Human ancestors not to blame for ancient mammal extinctions in Africa

Finally we can stop being guilty about SOMETHING~ctm

From Eurekalert

New research finds grassland expansion drove the decline of giant mammals over the last 4.6 million years
University of Utah

New research disputes a long-held view that our earliest tool-bearing ancestors contributed to the demise of large mammals in Africa over the last several million years. Instead, the researchers argue that long-term environmental change drove the extinctions, mainly in the form of grassland expansion likely caused by falling atmospheric carbon dioxide (CO2) levels.

Tyler Faith, curator of archaeology at the Natural History Museum of Utah and assistant professor in the Department of Anthropology at the University of Utah, led the study. The research team also includes John Rowan from the University of Massachusetts Amherst, Andrew Du from the University of Chicago, and Paul Koch from the University of California, Santa Cruz.

The study is published today in the journal Science.

“Despite decades of literature asserting that early hominins impacted ancient African faunas, there have been few attempts to actually test this scenario or to explore alternatives,” Faith says. “We think our study is a major step towards understanding the depth of anthropogenic impacts on large mammal communities, and provides a convincing counter-argument to these long-held views about our early ancestors.”

To test for ancient hominin impacts, the researchers compiled a seven-million-year record of herbivore extinctions in eastern Africa, focusing on the very largest species, the so-called ‘megaherbivores’ (species over 2,000 lbs.) Though only five megaherbivores exist in Africa today, there was a much greater diversity in the past. For example, three-million-year-old ‘Lucy’ (Australopithecus afarensis) shared her woodland landscape with three giraffes, two rhinos, a hippo, and four elephant-like species at Hadar, Ethiopia.

When and why these species disappeared has long been a mystery for archaeologists and paleontologists, despite the evolution of tool-using and meat-eating hominins getting most of the blame.

“Our analyses show that there is a steady, long-term decline of megaherbivore diversity beginning around 4.6 million years ago. This extinction process kicks in over a million years before the very earliest evidence for human ancestors making tools or butchering animal carcasses and well before the appearance of any hominin species realistically capable of hunting them, like Homo erectus,” says Faith.

Taking a Closer Look

Faith and his team quantified long-term changes in eastern African megaherbivores using a dataset of more than 100 fossil assemblages spanning the last seven million years. The team also examined independent records of climatic and environmental trends and their effects, specifically global atmospheric CO2, stable carbon isotope records of vegetation structure, and stable carbon isotopes of eastern African fossil herbivore teeth, among others.

Their analysis reveals that over the last seven million years substantial megaherbivore extinctions occurred: 28 lineages became extinct, leading to the present-day communities lacking in large animals. These results highlight the great diversity of ancient megaherbivore communities, with many having far more megaherbivore species than exist today across Africa as a whole.

Further analysis showed that the onset of the megaherbivore decline began roughly 4.6 million years ago, and that the rate of diversity decline did not change following the appearance of Homo erectus, a human ancestor often blamed for the extinctions. Rather, Faith’s team argues that climate is more likely culprit.

“The key factor in the Plio-Pleistocene megaherbivore decline seems to be the expansion of grasslands, which is likely related to a global drop in atmospheric CO2 over the last five million years,” says John Rowan, a postdoctoral scientist from University of Massachusetts Amherst. “Low CO2 levels favor tropical grasses over trees, and as a consequence savannas became less woody and more open through time. We know that many of the extinct megaherbivores fed on woody vegetation, so they seem to disappear alongside their food source.”

The loss of massive herbivores may also account for other extinctions that have also been attributed to ancient hominins. Some scientist suggest that competition with increasingly carnivorous species of Homo led to the demise of numerous carnivores over the last few million years. Faith and his team suggest an alternative.

“We know there are also major extinctions among African carnivores at this time and that some of them, like saber-tooth cats, may have specialized on very large prey, perhaps juvenile elephants” says Paul Koch. “It could be that some of these carnivores disappeared with their megaherbivore prey.”

“Looking at all of the potential drivers of the megaherbivore decline, our analyses suggest that changing climate and environment played the key role in Africa’s past extinctions,” said Faith. “It follows that in the search for ancient hominin impacts on ancient African ecosystems, we must focus our attention on the one species known to be capable of causing them – us, Homo sapiens, over the last 300,000 years.”



145 thoughts on “Human ancestors not to blame for ancient mammal extinctions in Africa

  1. “New research finds grassland expansion drove the decline of giant mammals over the last 4.6 million years
    University of Utah”

    Humans planting lawn.

  2. “Instead, the researchers argue that long-term environmental change drove the extinctions, mainly in the form of grassland expansion likely caused by falling atmospheric carbon dioxide (CO2) levels.”

    Blamed the extinctions on varying CO2 levels? Oy vey!!

    [sarc on] Maybe they’ll come back now, with the elevated levels of CO2 [sarc off]

  3. also elsewhere said:
    “A transition from eating mainly vegetables and fruit to predominantly eating meat may have driven the evolution of humans’ big brains. ”

    hm,… have your kids first, then go vegetarian.
    no offence meant, that advice sounds a bit dodgy, … no I didn’t mean that…

    • vukcevic – November 25, 2018 at 6:14 am

      also elsewhere said:

      “A transition from eating mainly vegetables and fruit to predominantly eating meat may have driven the evolution of humans’ big brains. ”

      “HA”, those silly anthropologists and paleoanthropologists have been touting that silly arsed “circular reasoning” crapolla for the past 200+- years.

      “DUH”, …. eating lots of high protein meats, ….. to evolve an intelligent brain, …. so they could invent the tool, …… that they desperately needed for killing n’ butchering the savannah dwelling animals that they needed to eat to evolve their intelligent brains.

      Oh yeah, almost forgot, …… those early Homo sapiens had to evolve their bipedal running abilities after they invented their tools ….. so that they could chase down and kill their high protein prey animals.

      And soon after they invented their “killing” tools and evolved to run bipedally across that “hot n’ dry” African Savannah, …… they first had to invent “water bottles” and “salt tablets” to take with them so that they wouldn’t die from profusely “sweating” out the salt and water that their body needed for survival.

        • “Yes”, but only after it is killed, butchered and cooked via use of a fire.

          Craig from Oz, go to a supermarket, pick up a big beef roast out of the cooler …….. and try to take a “bite” out of it.

          Only then will you have an appreciation for the butchering, cutting and the cooking of high protein meats.

      • There are many ways to get meat into your diet.
        Chasing down and killing large prey is only one of them.
        It’s not that the anthropologists are engaged in circular reasoning, it’s more that you haven’t thought through your position at all.

        BTW, it will probably surprise you, but early hominids were walking upright millions of years before they started making tools.

        • MarkW, you can chase down and kill small prey IF ONLY you could run fast enough, but you would still need “sharp” tools to kill and butcher it before you could eat it. And after you had been eating that high-protein meat for 15 to 20 thousand years you might have been intelligent enough to INVENT those “sharp” tools that you originally needed.

          MarkW, you are absolutely correct that “early hominids were walking upright millions of years before they started making tools”, …… but they sure as hell wasn’t “walking upright” on the hot African savannahs during that “millions of years” of evolving to walk bipedally. Those savannah predators would have eaten them faster than they could have reproduced.

          Quit believing in “fairy tales”.

          • Samuel,

            The fairy tales are all yours.

            Our bipedal savannah ancestors were indeed vulnerable to predators, but we enjoyed the refugee of trees when need be, in the mixed grassland and woodland savannah environment in which they evolved.

          • John T, ….. following is commentary that I am the author of, now you have the choice of either IGNORING it, ……. or reading it and then explaining why you consider it nothing more than “a fairy tale”, to wit:

            The evolution of bipedal locomotion, loss of protective body hair and the growth/formation of “sweat glands” over their entire epidermal skin area are just three (3) of the physical attributes that our early human ancestors (the only living sub-species in the Family of Great Apes) acquired during the past two (2) million years, ….. for them to best survive in the environment that they chose to live and reproduce in.

            So, the question is, what was their selected environment like that best suited a bipedal stance or movement, ….. did not require the protection of a heavy coating of body hair, ,,,,, but absolutely, positively required that their entire body surface (epidermis) contain sweat glands that secrete copious amounts of salt (NaCl) containing water (H2O).

            Surely that environment was not a hot, semi-arid African savannah, …. simply because salt (NaCl) and water (H2O) are the two (2) most important, precious resources necessary for pre-human or human survival, ….. and thus it would be highly detrimental to one’s survival if they indiscriminately rid their body of said without an immediate means of replacing said losses. Too little, or too much water (H2O) or salt (NaCl) is a cause of certain death to humans.

            As far as anyone knows, ….. the evolving of “sweat glands” in the epidermis covering of the human body may have specifically evolved for ridding the body of excess salt (that was/is ingested as a result of their primary food source) …… because the retention of too much salt will kill you “deader than a door nail”, There has been more than one (1) human that has died from drinking “salty” water. And a “heat stroke” is the result of “sweating out” too much of the body’s salt content.

            If one is only focusing on or only considering “human furlessness”, …. then I agree, one will not readily see anything particularly aquatic about it. And the same goes for human bipedalism, you won’t see anything particularly aquatic about it either. But you can’t be “focusing on” human furlessness or bipedalism if you are going to apply a kind of “reverse evolution” to determine the environmental “driver” of said attributes. Thus said, one has to focus on the “environmental driver(s)” responsible for the evolved attributes, …… and not the attributes themselves.

            Thus, it is of my learned opinion that human “furlessness” is a direct result of human “bipedalism”. In other words, human bipedalism was the “environmental driver” responsible for human furlessness.

            And I say that because, if our early human ancestors had never evolved the ability of bipedal walking over the course of 300K or a million years, ….. then there would not have been any logical reason (environmental driver) for their body to evolve furlessness. Human bipedalism and furlessness go “hand-in-hand”, no need of one without the other.

            And, the next obvious question that I am sure you will want me to provide an answer to/for is: “And just what is the “environmental driver” responsible for human bipedalism?”

            And the simple answer to the aforesaid question is, ….. our early human ancestors, which eventually evolved to be a sub-species of the Family of Great Apes, established a close association with an aquatic environment by taking up residence on or near the shoreline of a river, lake, tidal zone, estuary or inland sea simply because said body of water (H2O) provided them an easily accessible, abundant supply of high-protein foods that did not require the expenditure of great amounts of time and energy, …… or the use of tools, …. for harvesting said food or for eating of said foods. Life is good …… for any animal species that doesn’t have to spend all their waking hours searching for food and evading predators.

            And bipedal walking evolved as a result of ….. harvesting their food from the shallow waters. It is quite easy to learn to walk bipedally by walking (wading) in water because the water provides buoyancy to easily hold oneself in an upright position. And thus, our early ancestors that were the best bipedal waders/walkers in the water ……. were also the bestest provider of aquatic foods ….. and the bestest food provider got to do the mostest procreating with the females.

            Loss of body hair/fur by early humans resulted in the loss of a protective covering of the epidermis, which meant that it would have been highly improbable for early humans to walk or run amongst or through the brush, weeds, thorns, briars, etc., of the hot/dry African savannahs while looking for tubers or fruits, …… or either trying to catch a prey animal or trying to evade a predator animal ……. without their “bare” skin being cut, scraped, gouged and/or lacerated …. which would have surely resulted in their demise. Loss of body hair/fur also meant a loss of protection from blood-sucking and biting insects that commonly inhabit brushy fields, grasslands, savannahs and hot/humid locales.

            Loss of the majority of body hair/fur by early humans meant that they could more easily walk or wade bipedally in the water when harvesting aquatic foods. Heavy or thick body hair/fur would cause a severe “drag” on quick movements required to capture aquatic prey animals, especially in deep water.

            Humans retained their body hair under their arms and between the legs in their groin area simply because said patches of hair serves the purpose of a “dry lubricant”.

            And humans retained their body hair on their head most likely because of their bipedal stance. It protected their head and brain from the solar irradiance …… as well as providing a “glare reducing” aid or shield when bipedally walking in the water harvesting their food.

            “YUP”, the harvesting of their aquatic grown foods whose remains provided them with a variety of “natural tools” (bivalve shells, spines, claws, fish bones, etc.) that didn’t need any “inventing” by those early humans, …… who just had to figure out how best to use them for other purposes. And they had plenty of “free time” to do their “figuring” ….. because they were not spending all their awake hours searching for food and evading predators.

            It is utterly asinine and idiotic for anyone to claim that our early pre-human ancestors expended 200/300+ thousands of years on the African savannahs, at first evolving to walk bipedally, then to run bipedally, in order to chase down, kill and butcher Savannah living animals in order to acquire a sufficient source of high-protein foods, …… that they required for evolving a large brain and greater intelligence, ……. that was prerequisite to them being capable of “inventing” the tools ….. that was absolutely, positively necessary for the killing and/or butchering of the aforesaid animal protein.

            Cheers, …… S C Cogar

          • I don’t have an opinion on this “debate”, but I did find this video to be both amusing and informative, and it offered a pretty cool take on one aspect of this discussion: what factors help make humans dominant.




          • @ ripshin

            Sorry bout that, but I don’t watch videos on my PC, because ….. Upload speed is only 0.38 mbs

          • It doesn’t matter, my download speed is only a whopping 1.53 mbps

            Too bad I’m not a retired government employee with a 6-figure retirement check so as to afford a quickie IP.

          • ripshin November 27, 2018 at 6:24 am


            That was fun.

            Human lack of fur on most of our bodies is clearly part of our adaptation to long distance running, with our evaporative cooling system, not because we went through a marine or aquatic mammal phase. Our ancestors did however exploit aquatic and marine resources. But we didn’t live in the water.

          • John Tillman – November 28, 2018 at 7:59 am

            Human lack of fur on most of our bodies is clearly part of our adaptation to long distance running, with our evaporative cooling system

            John Tillman, what is it that you refuse to accept/understand about ….. hairless humans, long distance running, extremely hot near-surface temperatures and the over-heated human body SWEATING OUT copious amounts water (H2O) and salt (NACL), …… two (2) of the most precious commodities required for maintaining one’s life.

            And the above was “true” about the physiology of our early human ancestors of 40,000 to 2 million years ago …… and it is still “true” about the physiology of present-day humans.

            Tell ya what, …… John Tillman, ……. prove me wrong, ….. and prove to yourself that you can bipedally run around on oval athletic track for 2-3 hours, ….. on a “hot” Sun shining day, without the aid of a water bottle and salt tablets, …… and without any fear of succumbing to dehydration or hyponatremia.

            And iffen you attempt to do that, do you know what they will call you? “HA”, they will call you an ambulance because you will surely need one.

            Hyponatremia is a condition characterized by low levels of sodium in the blood. Its symptoms are similar to those caused by dehydration, and in severe cases the brain may swell and lead to headaches, seizures, coma and even death.

            Risk factors for dehydration include exerting oneself in hot and humid weather, endurance athletics. Most people can tolerate a three to four percent decrease in total body water without difficulty or adverse health effects. A five to eight percent decrease can cause fatigue and dizziness. Loss of over ten percent of total body water can cause physical and mental deterioration, accompanied by severe thirst. Death occurs at a loss of between fifteen and twenty-five percent of the body water

          • John Tillman – November 28, 2018 at 7:59 am

            Human lack of fur on most of our bodies is …….. not because we went through a marine or aquatic mammal phase.

            BUT, BUT, BUT, …… John Tillman, ……. the gestation period that every human fetus has to endure, …… is, ……. in actuality, ……. an aquatic mammal phase.

            “DUH”, to wit, ….. “During pregnancy, your baby is surrounded and cushioned by a fluid-filled membranous sac called the amniotic sac. Typically, at the beginning of or during labor your membranes will rupture — also known as your water breaking.

            Our ancestors did however exploit aquatic and marine resources. But we didn’t live in the water

            You messed up, ……. John Tillman, …… you should have stated all of what you were taught to say, which was: “But we didn’t live in the water and we didn’t evolve from monkeys.

            And ps, ….. just where on the hot, dry African savannahs did our early human ancestors find aquatic and marine resources to be exploiting?

            “DUH”, Africa’s Great Rift Valley is not comprised of hot, dry savannahs.

          • Samuel,

            Sorry you’re not able to watch online videos, I too had poor internet for years and missed out on a lot of really interesting and informative things.

            At any rate, to summarize the point the zoologist makes in the video (though he does much more humorously and authoritatively than I can), the ability of humans to sweat give us an endurance bonus unequaled in the animal kingdom and is presumed to be a net benefit to our advancement and evolution. Whether that, in itself, speaks to the origins of our ancestors is debatable, but the point being made is it’s a feature not a bug.

            I suppose when you consider that the only reasons to run were to escape a predator or chase prey, with both being relatively short durations, the negative consequences of sweating can be seen as positives. (In that it enables higher endurance.) However, it’s also clear that rapid replenishment of water, and yes, salts, would have been required.

            Interesting topic for sure.



          • @ ripshin – November 29, 2018 at 1:15 pm

            Thanks for your kind response, …… and my parting words on the subject …… concerns this statement about the video, to wit:

            the ability of humans to sweat give us an endurance bonus unequaled in the animal kingdom

            Ripshin, the above makes no logical sense. For early humans to take advantage of said “endurance bonus” they would have had to carry containers of salt and water with them when they were doing the “chasing” ……. but it wouldn’t help them one bit if they were the ones being chased. Bipedal running cannot outpace quadrapedal running (unless you are an ostrich).

            To correctly figure out how things evolved, one has to logically “reverse-engineer” (reverse-mutation) the evolutionary changes.


        • MarkW,

          Right, if you specify stone tools.

          As chimps make tools, IMO the key distinction between australophithecines and genus Homo is stone tools. Although some have cited evidence for genus A. making and using stone tools.

          Our australopithecine ancestors should probably be included in Homo. Indeed, many argue for congeneric status of Pan and Homo. Among them were Linnaeus, but he knew he’d run afoul of religious authority if he classified humans and chimps in the same genus.

      • What helped brain development was fat, acquired from scavenging megafaunal carcasses as well as hunting and gathering.

        H. erectus’ hand axe was a tool of many uses, but among them was smashing long bones to get at the marrow.

        • What helped brain development was fat, acquired from scavenging megafaunal carcasses

          Shur nuff, ….. John T, ….. and they screamed “BOO”, … “BOO”, … ”BOO”, … to scare off all the buzzards, vultures and other predators vying for a mouthful of dead meat.

          “Yup”, intelligence at its bestest, claiming that 15K to 50K years of snitching a bite of fat meat every now and then ….. was plenty more than enough to nurture the evolution of a large, intelligent thinking brain.

          And “Yup”, those flint hand axes were also great tools for killing large aquatic animals such as sturgeons, salmon, etc., …… that that is why the majority of those flint hand axes have ben found in stream and river beds/channels.

          • No salmon or sturgeon in East and South Africa, from whence come the first hand axes.

            Nor are they ideally suited for processing such fish.

            Please cite a source for your claim that a majority of hand axes have been found in stream and river bed channels. My impression is that those at Olduvai at least were from living areas. There were intermittent dry lakes in the area, of course.

          • My impression is that those at Olduvai at least were from living areas.

            John Tillman, an expertly napped flint axe of yesteryear …… would be the equivalent of a fine hunting rifle now days, …… and the owners take great care of them and they are passed down to relatives or traded for goods or services, lost or stolen. But never discarded as trash in one’s living area.

  4. The Miocene and Pliocene spread of grasslands is associated not just with less CO2, but cooler and drier conditions.

    However, Africa still has two rhino species. Whether the modern giraffe consists of one species or many is controversial. But a number of giraffe species in Africa and Asia went extinct after the advent of anatomically modern humans.

    It’s also possible that humans wiped out the largest member of the elephant family, and possibly biggest land mammal of all time, in Asia:

    • JT: ” … but cooler and drier conditions.”

      Agree, take away the rain for a few years and you get bare dirt and dead animals.

      • Still rains in East Africa, but just not all the time, rather seasonally. Compare and contrast still forested Central and West Africa. Some blame the Rift Valley from c. 8 Ma for drying out eastern and southern Africa. Others global cooling from the Oligocene onwards.

        The lakes of the Rift Valley separate the savannah habitat of our upright walking ancestors from the woodland biome home of chimps.

        • Yes, of course, but we’re talking about actual climate change, where the rain can drastically decrease for a few centuries or fluctuate sharply for millennia. In other words, chronic water stress with a strongly-punctuated population dynamic and ‘trajectory’, that eventually ends in local extinctions that extend to a general species extinction of a core component or two of the food chain, which pushes others to extinction (dominos style).

          Add predation pressure by humans to the mix (scale and significance unknown) and you get another pressure. And as I’m sure you know, it isn’t either or, as many seem to argue, it’s clearly both. Humans were probably a minor player but not a non-player, in the demise of the species.

          So IMO its clear that pronounced and chronic issues with precipitation change could produce this outcome and CO2 change is not required (at all) to explain it, although it is a (smaller) factor. If we apply the Okham’s Razor rule we should say that precipitation changes are the simpler more complete thesis. Removing rainfall, or most of it, is a killer of habitat and range extent—we already know this, and it could not be clearer. So I don’t see why this article, and other people, are invoking lower CO2 to explain the demise (or to explain glacial dustiness) when precipitation changes can already do this (rift topo changes being a part of that of course), and is the much more convincing and complete mechanism.

          No rain produces dead plants and dead animals, and less trees. So it’s not so much a “development of grasslands”, but a demise of trees, which again a punctuated and chronic precipitation stress for a few ky can easily account for.

          See this also (my post never reappeared so I wrote another):

          • WX,

            IMO and that of those who’ve studied extinction of the Pleistocene megafauna, humans are primarily responsible. The same species survived the much warmer and longer Eemian interglacial and in many cases previous ones as well. Only when human hunters are added to climatic stresses did mass extinction of large animals occur.

            As to whether cold and drought sufficiently explain the evolution of new species and extinction of old during the Oligocene to Pleistocene, or whether falling CO2 were also a factor, I can’t say. But it seems reasonable, as C4 and CAM plants evolved during those epochs to conserve water and make more effiient use of lowered CO2 levels.

          • John..I find most of your argument valid and probably correct in the final analysis with early Man delivering the final blow to the megafauna everywhere. Especially on some the smaller tropical islands, it is without question. However, how would we ever know now if the megafauna had been severely distressed over multiple ice age advances since the Pleistocene began with lowering CO2 and climate suitability leading to diminished habitat and food supply/chain issues because of cold and drought due to lower CO2 over the last 1-2 million years? Which would make them a lot easier to be hunted to extinction if they were already on a slow route to natural extinction with lower numbers and declining habit. How would we know with any certainty, especially in the continental new world, that it isn’t a combination of both? Why can’t it be a combination of both lower, less resilient populations and early human hunting pressure delivering the final blow?

          • E2,

            IMO we can have confidence that the megafauna would have survived the Holocene, just as prior interglacials, without the intervention of human predation.

            CO2 didn’t get materially lower during the last glacial maximum than during prior maxima, if at all. Nature provided us with a controlled experiment. The same species wiped out during the last glaciation and transition to the current interglacial survived the much warmer and longer Eemian and often prior interglacials even more temperate and longer lasting.

            IMO it’s a simple QED. Proponents of climate change as the killer will persist, thanks to the ruling paradigm and the bucks it brings, but IMO any dispassionate analysis has to recognize the new variable in the equation, ie anatomically modern hunters.

            Whether it be isolated islands (the Caribbean, HI, Mauritius), microcontinents (Madagascar, NZ) or continents (Oz/New Guinea and the Americas), the story is always the same. It takes, IMHO, willful denial of reality to reject the obvious conclusion.

            Climate change does stress big animals, but they have always enjoyed the option of migrating during past intervals of colder and warmer conditions. Humans gave them no such refuge. Paleolithic modern humans were superpredators, then as we are now.

            No alternative explanation can explain the demise of the big beasts and persistance of the little ones. No other story can tell why the late Pleistocene and Holocene suffered such catastrophic losses, but not the Eemian or earlier transitions. No other hypothesis says compellingly why ground sloths, for instance, were wiped out on the mainlands of the Americas when people first arrived, but not on Caribbean islands until we managed to get there, too.

            But please provide an alternative explanation, if you can conjure one. Thanks!

          • I just had a post “disappear”, but I’m pretty sure it will reappear.

            It does that every time I refer to our early ancestors as ….. H— sapiens.

          • Samuel C Cogar
            Perhaps if you said “Hominidae” instead of “H–“?
            (Or even “Shomo”, or “Itomo”, or …)

          • Maybe CTM and the Mods (sounds like a groovy rock band) are just getting to the bit buckets and now a few hundred comments are all going to show up at once. lol

    • Nobody denies that humans today are able to wipe out species on a regional or global scale. But that requires literally hundreds of millions, if not billions of humans, plus the supporting technological infrastructure to support such large populations in to create that kind of environmental change.

      In “ancient times” – whatever that is – there simply were not those kinds of numbers. The systems of human organization – towns, and governments stretching across entire regions – and technology – mainly agriculture, and animal husbandry, wheels, and metal tools and weapons – necessary to support a large enough hominid population to fosterglobal species and ecosystem wipeouts did not exist across most of the planet until just the last several thousands of years.

      The critter you provided a link to died out about 24,000 years ago according to the fossil record, and its population was spread across three continents. Blaming its demise on humans is mere speculation and conjecture, as there is zilch scientific evidence to support your conclusion. The entire earth’s population of humans 24,000 years ago can only be roughly estimated, but it is something well under 1 million for the entire planet. That works out to a population density worldwide of less than 2 times ten to the minus eighth humans per square mile. Not conducive to wreaking catastrophic impacts on global species.

      • Correction – my math was in error … the human population density 24,000 years ago across the entire land area of the planet worked out to less than 1/57th person per square mile. Still infinitesimal.

        Of course, humans were not uniformly spread out across the entire land surface of the planet, but were concentrated in livable environments. But the ancient megafauna cited in the link was itself spread across Europe, Asia, and Africa, which were the habitable parts of the planet but for the Americas, which was just seeing the initial migrations from Asia 24,000 years ago.

      • “Nobody denies that humans today are able to wipe out species on a regional or global scale.”
        Thanks to Mikhail Kalashnikov :<)

        • I do think that it was a case of diminishing CO2 for a few million years of successive ice ages that finally wore down the ancient Megafauna that allowed early prehistoric Man to finally finish them off with hunting during and after the last age when they were at their weakest. It wasn’t one or the other, but a perfect storm of events that finally did them in, because they were also in serious population decline already due to CO2 starvation of their plant food or food chain as well as incredible pressure on habitat as the ice ages took their toll on general habitat and populations everywhere simultaneously. If the ancient megafauna had been as healthy as the Plains Buffalo had been, it is possible they would have all survived until the arrival of the rifle. It is usually never one thing or another, but a piling on of successive pressures that cause an extinction.

          • Had all the American Indians in AD 1500 been concentrated against even the vast herds of bison on the Great Plains, as Paleoindians were against the megafauna, the “buffalo” too would have been toast, as they almost were in decades against 19th century tech, not that much more effective than atlatls and stampeding with fire or drives.

            Modern humans are deadly, no matter whether with stone-tipped weapons or lead rifle bullets.

      • Not speculation.

        Hunter gatherers from ~60,000 to 10,000 years ago wiped out the megafauna of Australia and the Americas, and much of them in Asia and Europe. Small numbers of agriculturists then did the same in NZ and on other oceanic islands.

        As for Paleoloxodon, it went extinct during the Last Glacial Maximum, but its tropical and subtropical habitats weren’t greatly affected by the colder climate, which was already cold. The difference from the prior glacial maximum some 100,000 years previously was modern human hunters in its environment.

        • Jonathon Tillman.

          The claim that humans “wiped out the Australian megafauna” is also speculative.
          We have no observation. We have no records. We have no time machine.

          All we have is a little evidence of interaction and some potential – but loose -correlation WRT timing…… and as any student of logic knows, Correlation is not proof of Causation.

          The discussion of extinctions is very, very like that about Climate Change. Everyone is happy to accept hundreds of millions of years of extinctions for perfectly natural, Darwinian, reasons – but as soon as humans appear on the scene, every extinction becomes our fault.

          • Peter,

            As noted elsewhere, we have causation as well as correlation.

            LNot every extinction is our fault, of course. But most Pleistocene megafauna, yes. Losses in the late Pleistocene were way outside background extinction, and preferentially among the biggest game. These species had survived previous glacial-interglacial transitions.

            In this case, the overwhelming preponderance of the evidence is that humans were indeed responsible for late Pleistocene and Holocene mass extinctions.

          • You only believe that you have causation.
            The mere fact that humans hunted an animal is not proof that humans caused it to go extinct.

        • Anyone that thinks humans from 20,000 years ago hunted to extinction rhinos, elephants, et al, have nearly seriously contemplated running up to said creatures and trying to poke them with a sharp stick.

          • Agreed.
            But projectile weapons – where I do not need to even contemplate running up to said creatures and trying to poke them with a sharp stick – were a game changer.
            Earliest bow and arrow? IIRC [and I am not sure] but possibly 100,000 years ago. Of course, that was not the Olympic bows of today – but the folk back then would have gradually improved the weapons.
            It was in their interests.
            So, one day, enough arrows, and an elephant could be taken down.

            The other factor I wish to mention is naivety.
            Animals unused to humans – certainly in Australasia, Madagascar, isolated islands [like New Zealand] and perhaps elsewhere – would allow humans to approach almost to touching distance.
            Especially multi-tonne ones that have no fear of any animal in their environment once adult.

            None of this proves that humans did indeed eliminate megafauna.
            I think that, in NZ, humans were responsible [perhaps with commensal rats etc.] for the extinction of moas.
            Australia – in my view [and YMMV], humans were at least partly responsible – and there was climate change going on then.
            The Americas – well, naive animals suddenly encountered a full big-game hunter technology, about 11-14,000 [ISH] and most of the megafauna has vanished.
            Correlation is not Cause.
            But – what else was there to strike down these large animals?

            Again, YMMV.


          • That bison still roamed in large numbers in AD 1800 does not mean that their much larger ancestors and other megafauna even bigger weren’t wiped out by people. Ancient buffalo jumps show that they were. One reason that bison herds grew so vast is that Pleistocene compeitors had been wiped out.

            The evidence in Australia and the Americas isn’t coincidental. We have actual kill sites, with, for instance, Clovis points inside mammoth carcasses.

            But even if it were only coincidental, what is the most reasonable conclusion to be drawn from the fact that mass extinctions followed human occupations of Australia, North America, South America, the Caribbean islands, New Zealand, Hawaii, Reunion, Madagascar, etc?

            The animals which went extinct after the arrival of humans had survived prior climatic swings greater than those of 60 to 10 thousand years ago. And there was no meaningful climate change for the mass extinctions on islands in the second half of the Holocene, especially in the tropics. But not even associated with the loss of Stellar’s sea cow in the subarctic.

            We also have mammoth kill sites in Eurasia, to include in its far north as long ago as 45,000 BP. As with the near extinction of the American bison, concentrating on killing females in a population already under other stresses is a sure fire prescription for wiping out a species.

          • If any animal lets a human get close to it, it isnt because they are unused to humans, it’s because they are unused to predators. No wild animal that grows up with predators of any type will let any unfamiliar animal get close to it. As for bows and arrows, none of them could penetrate deep to inflict a fatal wound on something like an elephant.

          • SUP,

            Sadly, history is replete with naive animals lacking fear of humans.

            Mammoths weren’t brought down with arrows, but with atlatl darts, which do penetrate pachyderm skin.

          • auto – November 25, 2018 at 1:02 pm

            The Americas – well, naive animals suddenly encountered a full big-game hunter technology, about 11-14,000 [ISH] and most of the megafauna has vanished. Correlation is not Cause.

            But – what else was there to strike down these large animals?

            auto, ….. or anyone else who wishes to know “what else”, …… other than a few widely dispersed tribes of scraggly “bow & arrow” hunters, ……. could have been, and surely was, …… highly detrimental to the resident populations of megafauna, ….. just “click” on this hyperlink to view a composite graph of the Post Glacial Sea Level Rise and the proxy temperature graph of the Younger Dryas, …… which means said megafauna was subjected to both a 60+ meter rise in sea levels and a brutally cold period of ice n’ snow, accompanied by an extreme decrease in biomass growth, which would have DIRECTLY affected the herbivore prey animal populations, resulting in said megafauna ALSO dying of starvation.

            Just imagine how many humans would die if there was a repeat of the Younger Dryas.

          • Elephants killed with single [shots] from bow and arrow:


            It would be even easier to put a sneak on mammoths totally unused to human hunters. And ancient bows could have heavy draw weights, since men trained from boys in their use. The weights of English Medieval war bows were astonishing, and the archers using them practically deformed, not only by musculature but some unfused bones. The long bow is a self bow, made from one stave containing both sapwood and heartwood, in the same way as the most ancient of bows.

            And of course herd animals can be stampeded with fire or by drives off cliffs or into blind canyons.

          • auto November 25, 2018 at 1:02 pm

            I hope my links appear showing that a large African elephant can be killed by a single arrow.

          • Also, modern bison were no longer naieve. American Indian hunters had to sneak up on them to get close enough for a kill before the arrival of horses and firearms. Or stampede them over cliffs.

          • John Tillman – November 25, 2018 at 5:09 pm

            That bison still roamed in large numbers in AD 1800 does not mean that their much larger ancestors and other megafauna even bigger weren’t wiped out by people.

            The evidence in Australia and the Americas isn’t coincidental. We have actual kill sites, with, for instance, Clovis points inside mammoth carcasses.

            So what, Otzi “the iceman” was found with a flint projectile point imbedded in his cadaver, but that doesn‘t prove that the majority of northern Italy’s population succumbed to “bow & arrow” villians.

            John Tillman, iffen you are going to be touting those highly subjective claims about the demise of the megafauna, ….. you really, really need to cite some creditable estimates of said human population numbers verses the megafauna population numbers ….. because ya can’t be claiming that 30K to 80K early Amerindians ……… was responsible for the extinction of 150K to 400K megafauna predators.

            And keep in mind that, ….. given the age of sexual maturity of the offspring, …… with the exception of elephants/mastodons, ……. both the megafauna predators and their prey, could out-produce (birth) humans like 4 to 1.

            Sexual maturity of most all megafauna predators and their prey, ranges between 2 and 4 years of age, ….. whereas the sexual maturity of early humans ranged between 12 and 15 years of age.

            And the majority of early humans couldn’t keep “reproducing” much past 15-20 years of age ……. simply because their “life expectancy” was mighty short during those turbulent times.

          • StandupPhilosopher November 25, 2018 at 5:27 pm

            Herbivores with no reason to fear possible predators not only don’t avoid them, but seek closer contact with them, out of curiosity.

        • John Tillman –November 25, 2018 at 8:24 am

          Hunter gatherers from ~60,000 to 10,000 years ago wiped out the megafauna of Australia and the Americas,

          John T, …… do ya suppose those real early native Americans didn’t like the taste of “bison burgers” or “buffalo steaks” ….. because there was like 80 million of those big ole hairy grass eatin beasts on the western prairies when the Europeans came on shore?

          The native Americans were NOT killing very many of them until after they got hold of horses that the Spanish brought over.

        • “Hunter gatherers from ~60,000 to 10,000 years ago wiped out the megafauna of Australia” …
          Where’s the evidence John? … there’s no depictions of mega-fauna game in Aboriginal cave paintings of any era … only fish, macropods and reptiles … and there’s no mega-fauna ‘kitchen scraps’ in aboriginal middens … this indicates that mega fauna were not part of the environment when aboriginals arrived in Australia … aboriginals arrived during the last glacial minimum, when most of Australia was cold, arid grassland … I suspect the mega-fauna had died out by then …

          • MarkW,

            My replies are still not posting, so again, the short answer and a link.

            It’s not just coincidental. We have kill sites, with Clovis points inside mammoth carcasses.

            In all the continental and island instances I’ve cited, coincidence alone shows the correlation, but there is also evidence of causation. As with Oz, the evidence has become overwhelming that people caused the megafaunal extinctions of the late Pleistocene and Holocene.


            What was an hypothesis 50 years ago is now well established. No valid arguments are left against the “overkill” scenario.

          • That men hunted these animals is not in dispute.
            That this hunting resulted in extinction is. Once again, you have no evidence, just a lot of fanciful imaginings.

          • MarkW,

            I have all the evidence in the world. No fanciful imaginings required.

            It is not post hoc reasoning to point out the 100% correlation between humans entering new continents and islands with the extinction of the largest prey species and the predators which relied upon them. That’s a lot of coincidences:

            Australia, North America, South America, Madagascar, Caribbean islands, Hawaii, New Zealand, Reunion, Mauritius, etc. Note also that mammoths managed to survive on remote Arctic islands into the Holocene because there were no people there to hunt them. They couldn’t survive on the main Eurasian landmass. IMO it’s fanciful to imagine any other explanation for these observations than that humans entering habitats with naive large animals causes their extinctions.

            But I’d be happy to hear your explanation for the Pleistocene megafaunal extinctions. Thanks!

          • And I might yet again that the same species had survived previous interglacials by moving to habitats more conducive to their needs, ie, usually north onto the formerly submerged continental shelves.

            Note also that in the Americas, the largest and most slowly reproducing species went extinct first, eg mammoths, then the next largest groups were wiped out, eg Bison antiquus, stag-moose, camels, horses, ground sloths, etc. Probably same goes for Oz.

            An exception to this trend is mastodon, which survived longer, thanks to its forest rather than grassland environment. In South America, same applies to gomphothere.

        • There was another important distinction as the beginning of the present interglacial was interupted by the Younger Dryas.

  5. One of these days, when humanity comes to its senses over CAGW, we will be trying to figure out how to keep our atmospheric CO2 levels up sufficiently to feed the Earth’s population.

    China and India may be doing us a favor by burning all that coal.

  6. Very interesting study.

    Some key take-aways:

    1) You mean CO2 concentrations used to be a lot higher, before we humans started driving SUVs? WTF?

    2) Lower CO2 levels promote grasslands at the expense of forests, and vice versa. Most people would consider an increase in forests to be a very good outcome, right? More of the landscape we love, more of the critters we love that live in forests, much less boring to drive through or fly over, etc. etc. etc.

    3) This study begs the question: Has anyone ever quantified hominid population levels? For hominids to wipe out entire species and the ecosystems they thrive in, would there not have to be some pretty hefty populations of hominids to bring about such massive environmental change? I would seem to me that there would have to be millions of Lucy’s running about east Africa to make that kind of change, but I never see any studies that say, “Well there were __ million Lucy’s running about east Africa at that time.” Lucy and 10 or 20 or her cousins could not bring about the kinds of change that they’ve been blamed for causing.

    • Despite the decades of studies mentioned in this report, IMO few scientists have blamed early hominins for extinctions. That distinction generally rests with anatomically modern humans, or at least H. heidelbergensis-grade ancestors of moderns, Denisovans and Neanderthals.

      Lucy was more prey to predators than a threat herself to the megafauna with which she shared the spreading grasslands. H. erectus’ multitool “hand axe” probably did crush the bones of large animals to extract marrow, but more likely from scavenged carcasses than acctive hunting. Genus Homo did hunt, but not the biggest game.

      • To become effective hunters of megafauna would require some major species developments … aside from simply having the raw population numbers to overwhelm existing species, humans would have had to develop spoken language, necessary to coordinate the activities of multiple hunters necessary to bring down a large, dangerous beast, and also to pass down to succeeding generations the skills necessary for such effective coordinated action. Effective weapons would be needed, but the stone age weapons were certainly capable of harrying and killing a large beast by a sizeable coordinated human pack of hunters.

        Language development is only dimly understood at this time, and it is not known if it was sufficient 24,000 years ago to allow a wholesale slaughter of entire species of megafauna.

        The main drawback to human caused extinctions in that era really comes down to raw population numbers. There simply were not enough humans spread across Europe, Asia, and Africa to wipe out megafauna species that themselves were populated across those three continents.

        • All anatomically modern humans have the same biological basis for speech as do those of us living today. Language was just as complex 24,000 years ago as now.

          The hunters coming out of Africa weren’t spread evenly across the continents. They concentrated in a killing front wherever large, naive easy prey congregated. And they kept moving, following the game. This clearly evident in the Americas. Their numbers increased rapidly, thanks to abundant food.

        • Yet again my comment has failed to appear.

          The short version. Humans 24,000 years ago were just like us, but with slightly larger teeth. Their language abilities were the same as ours, shown by their anatomies, art and culture.

          They concentrated where the big game was, and their numbers rapidly expanded, thanks to all the food in the previously unpeopled continents.

        • Wolves manage to bring down prey many times larger than themselves without the benefit of a spoken language.

        • Duane – your logic about language is quite credible. However, if you look at the way wolves operate in packs to kill large herbivores like moose, you can see them doing it without much in the way of language. Of course, with language, hunting in packs can become much more sophisticated and efficient, but wolves are still doing not too badly.

          The development of language is perhaps one of the consequences of rapidly evolving intelligence, along with tools, weapons, social structure, fire, clothing, shelter etc. Intelligence, which gave our ancestors the ability to survive and prosper in tough glacial times, is the primary characteristic, and those other manifestations appeared because of the ability to think and make plans.

          A curious side effect of intelligence is the ability to believe in the supernatural, which we are now in the process of slowly outgrowing.

    • But the fallback safe position is to avoid saying that humans caused the extinctions, instead they say humans ‘contributed’ to them.

      If Lucy or her pals consumed even one grass seed that a megavore might have consumed, then early hominids have ‘contributed’ to their demise. Easy peasy.

  7. “drove the extinctions, mainly in the form of grassland expansion likely caused by falling atmospheric carbon dioxide (CO2) levels.”

    Once again, researchers or their vague press relations promote a possible assumption to correlation to causation.

    “the researchers argue that long-term environmental change drove the extinctions, mainly in the form of grassland expansion likely caused by falling atmospheric carbon dioxide (CO2) levels.”

    At least here they use a waffle word and appear to recognize how weak their presumptions are…

    Though, that presumption isn’t as weak as the paleo immediate assumptions that “mankind” is responsible.

    Welcome to reality, maybe.

  8. The closing up of the Isthmus of Panama 3.2 MYA and the start of the Pleistocene after that which led to lower CO2 levels because of cooling and glaciations probably had the most to do with it. When the Pacific Ocean didn’t flow directly into the Atlantic near the equator was probably the most significant geological event in 60 million years, along with the Himalaya uplift that happened much earlier. Much of Africa would have changed significantly to a much drier and grassland environment that was also responsible for the rise of humanoids. Humans didn’t have much to do with anything until at least 50,000 years ago. The start of the glaciations after the Isthmus closing up explains a lot of the last 3 million years, including the glaciations and vast changes to global climate that reduced habitat into the Pleistocene.

    • The Cenozoic ice age began at the Eocene-Oligocene boundary some 34 Ma, leading to Antarctic ice sheets. The world then started cooling and drying out globally, with profound effects on evolution and biomes.

      The closing of the Inter-American Seaway spread the ice sheets to the Northern Hemisphere, although Greenland might already have had at least and ice cap or caps in the Pliocene.

    • As the water was taken out of the system by the growth of ice Jungle area greatly reduced. Forrest became savannah, grasslands transitioned to desert. Cold times are dry times.

  9. Yes, repetitive, but by this time isn’t all of it?

    Politics, money, peer pressure and the lying, fact-free, fake news media’s censorship (BBC) have completely corrupted science. Climate change hysteria mongering has turned science, engineering and economics into full time bullshit factories.

    The Radiative Green House Effect theory contains a fatal flaw.

    For RGHE to perform as advertised requires the earth’s surface to radiate upwelling LWIR as an ideal black body, i.e. 1.0 emissivity at 16 C, 289 K, 396 W/m^2. (TFK_bams09)

    The contiguous presence of atmospheric molecules participating in non-radiative heat transfers through conduction, convection, latent renders impossible such BB LWIR, the effective surface emissivity being 0.16, i.e. actual 63 W/m^2 / ideal 396 W/m^2.

    The theoretical calculated “what if” ideal BB LWIR upwelling 396 W/m^2 does not exist – the 333 W/m^2 GHG energy loop simultaneously “warming” the surface and atmosphere does not exist – and the global warming and climate changes that are attributed to carbon dioxide do not exist.

  10. We must say Human Ancestors killed the animals because saying American Indians killed the animals would be insensitive.

  11. No no no no.

    “Mega critters ate ‘woody material” they say. That’s all we need to trash this thing, it is cr4p from the outset.

    Herbivores eat the leaves off of plants, the leaves being the ‘sugar factories’ and as such, the only place where there is any significant digestible nutrition. Sugar.
    Cellulose is not digestible and lignin even less so, *unless* you are A Termite OR A Mushroom (White Mould to be accurate)

    Are they *really* saying that these huge animals were expert tree climbers?
    Low hanging leaves/twigs/branches would rapidly be consumed, then what?

    The mega-critters *had* to be grass eaters.

    It was they who created the grassland and by being mega-critters could trash the trees in the search for ‘extra nutrition’
    Anyone who has ever kept a herd of cows will know what I’m talking about.

    But why did they trash the trees?
    Why did they need ‘extra nutrition’ What was in the trees that was not in the grass?

    Who knows, it could have been any one or more of the 52 different chemical elements that can and do go into making plants. The trees had it, the grass did not so they ate the trees to get the ‘missing something’
    Vitamin A perhaps?
    But trees only grow slowly compared to grass and baby trees would be eaten before getting 2 feet tall – hence the trees disappeared.
    But with them, went the missing vitamin from the mega critter’s diet and thence, so did they.

    Nothing to do with climate change, nothing to do with carbonoxide, nothing to do with hunters either and EVERYTHING to do with soil erosion.
    The dirt got old, weathered and eroded, the plants hit the Liebig limiting buffers on one or more vital soil nutrients and everything fell apart.
    Including the climate.
    Because, the trees (forest) created the weather. They retained moisture in themselves while alive and in the soil from fallen leaves, twigs, branches and other detritus. They then pumped it into the atmosphere and could create thunderstorms during the hottest part of the day even inside anti-cyclonic (High Pressure) weather situations. This kept them alive, also any grass that was nearby and thence forth, any critters that ate the grass, namely= The Megacritters.

    They wiped themselves out by trashing the trees looking for missing Vitamin X.

    Sound familiar……..

    I saw this story somewhere else a few days ago and in that version it mentioned how the consumption of critters made our brains larger than previously on a diet of vegetables.
    And NOT because we are carnivores.
    Like the Big Cats did and still do nowadays, we killed critters to get their livers, their blood, brains and to to suck on their bones.
    Like the cats now, we would reject the meat/flesh because it is tough to eat, hard to digest and a lot of protein can and does make you seriously ill.

    We got big brains from eating fat.
    We are Lipivores. Makes prefect sense coz that’s what brains are made of.

    What would anyone propose to happen if we gave up eating saturated fat?
    Brain shrinkage? Ooooh hello, sounds like Kwashkior
    Brain malfunction. like Depression and Paranoia. (Easily frightened)
    Self medication using addictive and harmful chemicals.
    Easily confused, leading to errors relating to Cause & Effect
    ‘Unreasonable behaviour’, especially as regards the opposite sex – leading to plummeting birth rates?

    A perfect description of this story here.Its got the lot.

    • Lot of common sense there, Peta.

      While it is true that low CO2 might favour the metabolics of grasses, the limit line between savannah and forest is more likely associated with precipitation nowadays, and probably was then. There might be a link between the two but it looks like the CO2 theory is seriously speculative. J Tillman’s contribution I also find very useful.

      Of course, I’ve not read the paper. Can anyone provide a link to the CO2 numbers they are using?

    • Herbivores, are further divided!
      Grazers eat grasses.
      Browsers may eat grasses, but they prefer woody materials.
      Not the solid wood portions as you infer, but the twigs, growing tips and leaves.
      Those portions are nutritious and have far less lignin than you claim.

      The entire deer family are mostly browsers, including the massive moose.
      Which is why deer visiting gardens eat the shrubbery and bushes, not your grass.

      “ELEPHANT: Loxodonta africana; DIET: Herbivore (browser), Leaves and fruits from trees and shrubs. Elephants will knock down trees if they cannot reach the leaves.”

    • @ Peta of Newark – November 25, 2018 at 8:39 am

      Great post, I liked it. When one offers their common sense thinking, intelligent reasoning and logical deductions in support of what they believe to be factual truths and evidence, ….. it always impresses me.

      To wit:

      We got big brains from eating fat.
      We are Lipivores. Makes prefect sense coz that’s what brains are made of.

      I never thought about “fat”, ….. coz 😊 I was always mimicking “high protein meat”, …. but from now on I will be stipulating “high energy fat” as the evolutionary “driver” of H. sapiens large, intelligent brain.

      And it doesn’t negate my belief of the “type of environment” that our early human ancestors evolved in, but on the contrary, it reinforces my belief that our early ancestors evolved in a “seashore” environment, at the edge of a salty inland sea, tidal zone or estuary, where they could easily harvest all of the HIGH fat and/or HIGH protein foods that they wanted to eat, without having to spend most all of their awake hours searching for something on land that was edible. Clams, mussels, oysters, lobsters, shrimp, urchins, eels, fish, etc., etc., were there for “easy pickings” ….. and they didn’t need any invented “sharp” tools to kill or butcher their food in order to eat it.

      And ps, …. fish skin, brains and roe are of “high fat content”. Grizzly bears take advantage of that “fact” when its Salmon “eatin” time.

      As a matter fact, it is only logical to assume that the exoskeletons of their food were the first “tools” that our early ancestors learned to use. (clam shells, spines, fish bones etc.) And bipedalism evolved out of the necessity to wade in the water for harvesting their food.


  12. Bond WJ, Midgley GF, Woodward FI (2003) The importance of low atmospheric CO2 and fire in promoting the spread of grasslands and savannas. Global Change Biology 9(7): 973-982.


    The distribution and abundance of trees can be strongly affected by disturbance such as fire. In mixed tree/grass ecosystems, recurrent grass‐fuelled fires can strongly suppress tree saplings and therefore control tree dominance. We propose that changes in atmospheric [CO2] could influence tree cover in such metastable ecosystems by altering their postburn recovery rates relative to flammable herbaceous growth forms such as grasses. Slow sapling recovery rates at low [CO2] would favour the spread of grasses and a reduction of tree cover. To test the possible importance of [CO2]/fire interactions, we first used a Dynamic Global Vegetation Model (DGVM) to simulate biomass in grassy ecosystems in South Africa with and without fire. The results indicate that fire has a major effect under higher rainfall conditions suggesting an important role for fire/[CO2] interactions. We then used a demographic model of the effects of fire on mesic savanna trees to test the importance of grass/tree differences in postburn recovery rates. We adjusted grass and tree growth in the model according to the DGVM output of net primary production at different [CO2] relative to current conditions. The simulations predicted elimination of trees at [CO2] typical of the last glacial period (180 ppm) because tree growth rate is too slow (15 years) to grow to a fire‐proof size of ca. 3 m. Simulated grass growth would produce an adequate fuel load for a burn in only 2 years. Simulations of preindustrial [CO2] (270 ppm) predict occurrence of trees but at low densities. The greatest increase in trees occurs from preindustrial to current [CO2] (360 ppm). The simulations are consistent with palaeo‐records which indicate that trees disappeared from sites that are currently savannas in South Africa in the last glacial. Savanna trees reappeared in the Holocene. There has also been a large increase in trees over the last 50–100 years. We suggest that slow tree recovery after fire, rather than differential photosynthetic efficiencies in C3 and C4 plants, might have been the significant factor in the Late Tertiary spread of flammable grasslands under low [CO2] because open, high light environments would have been a prerequisite for the spread of C4 grasses. Our simulations suggest further that low [CO2] could have been a significant factor in the reduction of trees during glacial times, because of their slower regrowth after disturbance, with fire favouring the spread of grasses.

  13. At last climate change you can believe in..?

    Looks like Stig may have found himself a good defence lawyer at last.

  14. Meh, man started with developing from “Nutcracker” man to to Homo Erectus about 2.5 million years ago eventually changing into the small meat eating units called Homo Erectus 1.8 million years ago, our teeth changed, bodies, everything to eat big things. Calories of elephants are in the millions, enough to feed a tribe. They got very very good at it. And wherever they went the size of animals got reduced as large meat bags mean major calories. Spears and eventually the throwing spear with Atlatl made short work of large mammals that previously when they got to a big enough size nothing could kill them, now they they ofter were slow moving calories for humans, and as we got better – species died out. When Modern Humans arrived in North America 15,000 years ago, the average mass of mammals fell from 216 pounds to just 17 over a very short time. In every single area, Africa, Asia, Australia, North America, everywhere humans and ancestors went the large mammals went away, giant meat bags that their size protected them now became the prize. Humans with spears and later dogs were a force that large animals that couldn’t run away fast enough died. What we have left is what can run away fast enough. Despite what media says, our ancestors didn’t respect the land or animals, they ate what they could and bred more that do the same. Evolution.

  15. Excerpted from: Human ancestors not to blame

    Instead, the researchers argue that long-term environmental change drove the extinctions, mainly in the form of grassland expansion likely caused by falling atmospheric carbon dioxide (CO2) levels.

    The loss of massive herbivores may also account for other extinctions that have also been attributed to ancient hominins.

    says Paul Koch. “It could be that some of these carnivores disappeared with their megaherbivore prey.”

    Did anyone else notice the “carefully chosen wording” in the above excerpted quotes?

    IMO, the authors didn’t want to offend those silly “old-school” anthropologists for the silliness that they have been preaching, teaching and writing about for past decades n’ decades.

    Of course, it is a literal fact that animal extinctions are primarily driven by “decreasing atmospheric CO2 quantities”.

    Of course, it is a literal fact that if the populations of massive herbivores begin drastically decreasing due to “decreasing atmospheric CO2 quantities” ….. then the populations of their predator animals will follow suite.

    The above “predator-prey” cycle is still common to this day, and the most well-known one is the “fox-rabbit” cycle that repeats itself every 8 to 10 years.

    With only a few foxes around, the rabbit population increases each successive year. That provides plenty of food for the foxes and the fox cub survival rate increases each successive year. After the foxes eat too many of the rabbits the foxes start dying off. And the cycle repeats itself.

    Now a month or 2 ago, I posted what I believe is a literal fact, and that is, a meteorite striking the earth 66 mya DID NOT CAUSE the extinction of the dinosaurs. Like stated above, …. “the dinosaur extinction was surely caused by falling atmospheric carbon dioxide (CO2) levels”.

    • Samuel Cogar, an obvious problem with your asserted “literal fact” is that paleoclimate reconstructions show that throughout the span from the last half of the Trassic, the full period of the Jurassic and the full period of the Cretaceous (the interval of 252 to 62 million years ago, commonly referred to as the “age of the dinosaurs”) the atmospheric CO2 content stayed in the very-comfortable-for-plant-and-animal-life range of 500 to 2500 ppm.

      If anything, there was a relatively marked increase in atmospheric CO2 at the Cretaceous-Paleogene (aka Cretaceous-Tertiary) transition:
      “Using the inverse relationship between atmospheric CO2 and the stomatal index of land plant leaves, we reconstruct Late Cretaceous-Early Tertiary atmospheric CO2 concentration (pCO2) levels with special emphasis on providing a pCO2 estimate directly above the KTB. Our record shows stable Late Cretaceous/Early Tertiary background pCO2 levels of 350–500 ppm by volume, but with a marked increase to at least 2,300 ppm by volume within 10,000 years of the KTB.” — extract from abstract of “An atmospheric pCO2 reconstruction across the Cretaceous-Tertiary boundary from leaf megafossils” by
      D. J. Beerling, B. H. Lomax,, (see )

      • Gordon,


        IMO Late Cretaceous CO2 was not that low, but clearly levels did spike after the bolide impact, from burning vegetation, release from carbonates struck by the collision and other causes. CO2 concentration remained high through the Paleocene and Eocene epochs, spiking at the PETM, then reaching even greater levels at Eocene peak.

      • Gordon Dressler – November 25, 2018 at 5:44 pm

        Samuel Cogar, an obvious problem with your asserted “literal fact” is that paleoclimate reconstructions show that throughout the span from the last half of the Trassic, the full period of the Jurassic and the full period of the Cretaceous (the interval of 252 to 62 million years ago, commonly referred to as the “age of the dinosaurs”) the atmospheric CO2 content stayed in the very-comfortable-for-plant-and-animal-life range of 500 to 2500 ppm.

        Gordon F, …… GETTA clue, ……. 500 ppm CO2 is not exactly comfortable for plant growth sufficient enough to feed those giant plant-eating dinosaurs that evolved when atmospheric CO2 averaged between 1,800 and 2,600 ppm. The dinosaurs started dying off after the CO2 started its drastic decline at around 190 MYA.

        Of course you and John Tillman will probably claim that both the published papers and included proxy graphs in the cited papers below, are nothing more than “junk science” tripe n’ piffle thst should be ignored by all, to wit:

        Geologic Global Climate Changes

        Climate and the Carboniferous Period

        • Samuel,

          Those standard CO2 reconstructions show your conjecture false. There not only is no evidence to support your baseless assertion that the non-avian dinosaurs were wiped out by falling CO2 levels, rather than a falling space rock. And all the evidence in the world against it.

          Not only is there no evidence of a decline in CO2 at the end of the Maastrichtian Age (end Cretaceous Period), but CO2 remained high in the following Paleocene Epoch, and well into the Eocene.

          Besides which, hosts of other groups also went extinct or suffered massive losses at the K/T (K/Pg now) boundary.

          While 500 ppm is below ideal, 2500 ppm is higher than needed for C3 plants. The optimal range is around 800 to 1300 ppm.

          • John Tillman – November 28, 2018 at 7:43 am

            Not only is there no evidence of a decline in CO2 at the end of the Maastrichtian Age (end Cretaceous Period), but CO2 remained high in the following Paleocene Epoch, and well into the Eocene.

            John Tillman, it highly irritates me when miseducated people attempt to “blow smoke at me” just to save face. You should have tagged your above paragraph as being “a joke”.

            According to both those CO2 proxy graphs I posted the urls for, CO2 was at 2,200 ppm at the end of the Jurassic Period (180mya), ……. and at 2,000 ppm at the start of the Cretaceous Period (150mya), ….. and began a steady decrease all during the remainder of the Cretaceous Period at 66mya, and then continued during the Tertiary Period.

            And the rise of CO2 at the start of the Triassic at about 252 million years ago “MARKS” the officially recognized beginning of the Age of the Dinosaurs, whereas, the extremely reduced CO2 at the end of the Cretaceous at about 66 million years ago “MARKS” the officially recognized end of the Age of the Dinosaurs.

            So, John Tillman, it is your choice, … you can continue deluding yourself by believing your nurtured “junk science”, ….. or you can embrace the factual science presented in the above 2 references I posted and/or the following published abstract, to wit:

            Concentration of carbon dioxide in the Late Cretaceous atmosphere


            Stable carbon isotope data from Late Cretaceous (Maastrichtian) palaeosols in India are used to estimate the concentration of carbon dioxide in the Late Cretaceous atmosphere. We show that the Maastrichtian atmosphere is unlikely to have contained more than about 1300 ppm by volume of CO2.This value agrees with an independently modeled value of CO2 in the Late Cretaceous atmosphere. A low concentration of the greenhouse gas carbon dioxide in the Maastrichtian atmosphere (relative to concentrations in the earlier Cretaceous) is consistent with palaeotemperature information from terrestrial plant and marine fossils, which suggest that the global climate cooled toward the end of the Cretaceous Period.


  16. North America and the Bison is a good point. It took modern man with firearms to redeuce the Bison numbers.

    While early man would have used fire to force e some animals over a cliff, mot of the time humans were prey not predeators,


    • I suspect that the North American Bison may have been pushed nearly to extinction by the very large population of Native Americans prior to European Contact. Most of these people had died out and their civilization crumbled in the 16th century due to European diseases, with most never even making contact with a European. This allowed the Bison population to surge, until Europeans began hunting them in earnest in the 19th century. The Plains Indians encountered were likely only a tiny fraction of the original population.

      • American Indians also managed the prairies with fire to increase wildlife habitat and make farming easier.

        I don’t know to what extent the mound-building Mississippian culture peoples might have exploited the Great Plains to their west, but most likely did, at least up the river valleys to some extent.

    • “Adam and Eve” aren’t meant to be taken literally, and the two didn’t live at the same time or place.

      Nor does that finding, if it might be called such, doesn’t necessarily imply an extinction. It just means that you have to go back a ways to find two ancestral animals from which all members of a species descend. Differing generation times should however produce different ages, although population size and litter number also matter.

      Also “hā·yə·ṯāh” occurs many times in the Bible, with various meanings besides “was” and “became”.

      It’s best rendered in Genesis 1:2 as “was”, as in at least two dozen English translations.

      • הָיָה hayah {haw-yaw}
        Meaning: 1) to be, become, come to pass, exist, happen, fall out 1a) (Qal) 1a1) —– 1a1a) to happen, fall out, occur, take place, come about, come to pass 1a1b) to come about, come to pass 1a2) to come into being, become 1a2a) to arise, appear, come 1a2b) to become 1a2b1) to become 1a2b2) to become like 1a2b3) to be instituted, be established 1a3) to be 1a3a) to exist, be in existence 1a3b) to abide, remain, continue (with word of place or time) 1a3c) to stand, lie, be in, be at, be situated (with word of locality) 1a3d) to accompany, be with 1b) (Niphal) 1b1) to occur, come to pass, be done, be brought about 1b2) to be done, be finished, be gone

        Usage: AV – was, come to pass, came, has been, were happened, become, pertained, better for thee;

        It is used in Gen 2:7 and translated “became” in the KJV plus many others.
        When הָיָה hayah is used, there is usually the sense of a “change”, a “becoming”. It’s not used as a simple statement of the past tense of “is”.

        The Bible doesn’t say a lot about what happened between Gen 1:1 and 1:2. A few things (ie 2 Peter: 6,7) but not much.

        We’ve drifted a bit from the main topic.
        To avoid a “food fight”, I promise the MODS that I won’t respond further to John or anyone else along these lines but I do ask that John be allowed a response to what I’ve said. (Assuming you allow this comment to remain.8-)

        • GD,

          It is not translated as “beccame” in the KJV or any other English translation with which I’m familiar. Here is the KJV translation:

          “2 And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.”

          Easily enough checked.

          The Bible says that Genesis 1:1-5 were all on the first day of creation.

          In Genesis 1, day and night exist on Day One, before the creation of the sun and moon on Day Four. Which is all the more remarkable, since the waters already existed, and the heavens were created on Day Two, then land and green plants on Day Three.

          • GD,

            Please feel free to free your tongue and see what biblical traffic the mods are willing to bear.

            Genesis 1 clearly has not just day and night before the sun, but also the plants reliant on sunlight for photosynthesis. Just a few of the ways in which it makes no sense in terms of observed reality.

            And then along comes Genesis 2, which contradicts Genesis 1 at every point. As do most of the rest of the mythological parts of the OT.

        • John,

          We’ve drifted a bit from the main topic.
          To avoid a “food fight”, I promise the MODS that I won’t respond further to John or anyone else along these lines but I do ask that John be allowed a response to what I’ve said. (Assuming you allow this comment to remain.8-)

          I stand by that.

  17. Creatures don’t just have to co-evolve with their large competitors and predators which leave conveniently observable skeletons. They also have to cope with all manner of evolving viruses, bacteria, and living critters at the small end of the scale. They are just as important, if not more so, for all these mammals today and yesterday. It’s very easy to attribute causality to the things you can easily detect, even when we now know how important these other factors are.

    Of course people used to have the simplistic view that populations didn’t vary wildly over even short time periods without some large external impetus. As with climate variations, that is known to be wholly incorrect, over short, medium, and long time periods. But it doesn’t stop people in the field pretending to not know it when they have a theory to sell.

  18. There seems to be an agenda to increase the role of climate change and CO2 levels in extinctions.
    I don’t buy it.
    Megafauna extinctions around the world have been shown to happen when human migrate to the area (at widely different times)
    If climate was the only factor then there would be some areas left for these animals could migrate to.

  19. From the Caveman chronicles -first documented jingle- “My Baloney has a first name- it’s Pachy- My Baloney has a second name it’s derms -Oh I love to eat them everyday – they’re so tame -an easy Prey- Cause Mainstream Science cannot say -Catastrophism is here to stay .

  20. I am relieved to know that my great*100,000 (+/-) grandparents are not responsible for the significant die-off in large mammals in Africa some 2.6 to 4.6 million years ago. A heavy weight has been lifted from my shoulders.

  21. An Alternative Theory: Man with Torch did it.

    The earliest hearth discovered so far is in Swartkrans Cave in South Africa and is dated 1.5 million years old. However, it is likely that hominids domesticated fire even earlier, as much as 2.2 million years ago. Our jaws and intestinal tracts are adapted to eating cooked food, (not big food). Our upright posture is adapted to carrying stuff in our hands — such as sticks for firewood into the caves where the hearths were.

    And if we could make fires in caves, we could absolutely make fire outside the caves, too. Like in the brush under the trees, in the grass, or anywhere we could get the landscape to burn.

    It was pre-dudes and pre-dudettes with torches that altered the vegetation — not CO2 levels. The anthro-burned savannas favored some quadrupeds and not others.

    Every other theory mentioned neglects the KNOWN propensity for fire starting by the only creature in creation that is ignition-enabled (and indeed totally fire dependent). Apparently all you so-called homo sapiens have forgotten about this.

    • Those who study extinctions have surely not forgotten. Please see my links to NZ extinctions below. Thanks.

  22. It think I’ve seen it written, that it wasn’t so much that “meat eating” lead to better nutrition and bigger brains…. It was the use of fire to cook raw foods, both meat and vegetable alike to make them more digestible and release more calories and nutrients. Raw meat is high in protein and hard for a body to digest unless it is cooked. It takes quite a bit of energy to digest meat and derive the protein from it.

    As for CO2 having an effect on plants rather than climate….. Yep, absolutely. We even see that today with satellites showing “greening” of the Earth, while statistics for crop growth also show CO2’s beneficial effects on Plantlife.

  23. Okay. So a megafauna prey/predator ratio is stable. H. Somebody shows up and starts after mammoth calves. Each time H. Somebody takes a mammoth calf, Smilodon is done out of lunch. H. S. isn’t a sportsman but a businessman, going after the easy ones. Like Smilodon, looking for the sick, lame, lazy, and clueless.
    Could a case be made that, first, Smilodon was erased by H. Somebody? Or if not Smilodon, some predator in roughly the same niche?
    So, at least at first, the prey/predator ratio might not have changed much, including the take quantified either as individuals or pounds of meat.
    Not until H.S. out took the local version of Smilodon would the pressure have led to reduced population.
    The reasoning about taking just one calf per H. S. every so often is interesting, but I wonder if it takes into account that a nursing female may not be fertile. Once her calf is dead, she no longer nurses and will be fertile sooner. So a replacement may come along relatively soon. To the extent she is not eating for two, marginally more resources are available for those who are. So that survival would, marginally, be more likely.
    A weaned calf is eating, except if it’s been killed, in which case somebody else gets the graze/browse. In a hard season, this may make the difference. Various hunter-gatherers we know of practiced infanticide, abandoning the old, and various kinds of birth control. Including the undergrads’ fave, Ritual Subincision Among the Arunta. Admittely, these are relict cultures driven to the edges of survivability. Not like our sturdy H. S., lord of protein plenty in fat city. There is no reason to dismiss the likelihood of a population of megafauna similarly living on the edge. And, paradoxically, being culled might have been a good thing.

    • Like American bison hunters, H. somebody would have taken not just calves, but their moms as well.

      Humans in historical times have wiped out many species. Ancient hunter-gatherers were also capable of killing too many large, naive beasts. Their weaponry and cooperative hunting skills were up to the task.

    • PS: The Pleistocene megafauna however weren’t wiped ou by H. somebody, but by H. sapiens sapiens, ie AMH, ie us.

      • If so, true as to Sap. But the article was talking about pre-Sap eras. So if it happened, it wouldn’t have been Sap.

        • RA,

          As above, I don’t think that Pliocene hominins wiped out any species. H. heidelbergensis, Neanderthal and Denisovan grade humans, maybe. But our species and subspecies, not only yeah, but Hell, yeah!

          As to extinction potential, not much difference between anatomically modern humans of 60 Ka and today. Main distinction now is that we’re aware of our devastation potential.

  24. JT is right.

    Also please note that one individual with a torch can burn a million acres quite easily if the setting is ripe. Every animal doesn’t have to be speared. H. something wasn’t a careful conservationist constrained with hunting and burning regulations. Those were the days…

  25. I don’t understand why the role of pathogens is almost always overlooked in the study of mass extinctions.
    When a new species, including hominids, enter an area, they likely bring new fungi, bacteria and viruses with them for which native fauna have no resistance.

    • Humans ourselves probably brought few pathogens with us dangerous to the indigenous fauna of most of North America, there being then few primates north of Central America. Our dogs however might have infected wolves, coyotes or even bears. Humans did however pick up pathogens from American animals. The syphilis spirochete is for instance closely related to that which causes yaws in bears (bacterial Genus Treponema).

  26. Recent (2016) further confirmation of Martin’s 1973 “Overkill” hypothesis:

    Test of Martin’s overkill hypothesis using radiocarbon dates on extinct megafauna

    Following Martin [Martin PS (1973) Science 179:969–974], we propose the hypothesis that the timing of human arrival to the New World can be assessed by examining the ecological impacts of a small population of people on extinct Pleistocene megafauna. To that end, we compiled lists of direct radiocarbon dates on paleontological specimens of extinct genera from North and South America with the expectation that the initial decline of extinct megafauna should correspond in time with the initial evidence for human colonization and that those declines should occur first in eastern Beringia, next in the contiguous United States, and last in South America. Analyses of spacings and frequency distributions of radiocarbon dates for each region support the idea that the extinction event first commenced in Beringia, roughly 13,300–15,000 BP. For the United States and South America, extinctions commenced considerably later but were closely spaced in time. For the contiguous United States, extinction began at ca. 12,900–13,200 BP, and at ca. 12,600–13,900 BP in South America. For areas south of Beringia, these estimates correspond well with the first significant evidence for human presence and are consistent with the predictions of the overkill hypothesis.

    • Martin actually first proposed the hypothesis in 1966. With each passing decade, it receives more support and confirmation not just for the Americas, but the Antipodes, parts of Eurasia, Africa and isolated islands and habitats.

      This despite the many who, for devotion to CACA, prefer to blame climate change rather than the “A” in CACA, ie anthropogenic factors.

    • At about the same time (1967), Belarussian climatologist M. I. Budyko, who later became notorious on both sides of the CACA hypothesis, proposed human hunting for the abrupt decline of Pleistocene megafauna in Eurasia:

      On the Causes of the Extinction of Some Animals at the end of the Pleistocene

      That’s right! The Soviets invented the overkill hypothesis first! As with all else.

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