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Image Credit: Wikipedia Image Credit: Anne Knock
From Live Science:
At Olduvai Gorge, where excavations helped to confirm Africa was the cradle of humanity, scientists now find the landscape once fluctuated rapidly, likely guiding early human evolution.These findings suggest that key mental developments within the human lineage may have been linked with a highly variable environment, researchers added.
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Scientists had long thought Africa went through a period of gradually increasing dryness — called the Great Drying — over 3 million years, or perhaps one big change in climate that favored the expansion of grasslands across the continent, influencing human evolution. However, the new research instead revealed “strong evidence for dramatic ecosystem changes across the African savanna, in which open grassland landscapes transitioned to closed forests over just hundreds to several thousands of years,” researcher Clayton Magill, a biogeochemist at Pennsylvania State University, told LiveScience.
The researchers discovered that Olduvai Gorge abruptly and routinely fluctuated between dry grasslands and damp forests about five or six times during a period of 200,000 years.
“I was surprised by the magnitude of changes and the rapid pace of the changes we found,” Freeman told LiveScience. “There was a complete restructuring of the ecosystem from grassland to forest and back again, at least based on how we interpret the data. I’ve worked on carbon isotopes my whole career, and I’ve never seen anything like this before.”
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The research team’s statistical and mathematical models link the changes they see with other events at the time, such as alterations in the planet’s movement.
“The orbit of the Earth around the sun slowly changes with time,” Freeman said in statement. “These changes were tied to the local climate at Olduvai Gorge through changes in the monsoon system in Africa.”
Earth’s orbit around the sun can vary over time in a number of ways — for instance, Earth’s orbit around the sun can grow more or less circular over time, and Earth’s axis of spin relative to the sun’s equatorial plane can also tilt back and forth. This alters the amount of sunlight Earth receives, energy that drives Earth’s atmosphere. “Slight changes in the amount of sunshine changed the intensity of atmospheric circulation and the supply of water. The rain patterns that drive the plant patterns follow this monsoon circulation. We found a correlation between changes in the environment and planetary movement.”
The team also found links between changes at Olduvai Gorge and sea-surface temperatures in the tropics.
Here’s the paper abstract
The role of savannas during the course of early human evolution has been debated for nearly a century, in part because of difficulties in characterizing local ecosystems from fossil and sediment records. Here, we present high-resolution lipid biomarker and isotopic signatures for organic matter preserved in lake sediments at Olduvai Gorge during a key juncture in human evolution about 2.0 Ma—the emergence and dispersal of Homo erectus (sensu lato). Using published data for modern plants and soils, we construct a framework for ecological interpretations of stable carbon-isotope compositions (expressed as δ13C values) of lipid biomarkers from ancient plants. Within this framework, δ13C values for sedimentary leaf lipids and total organic carbon from Olduvai Gorge indicate recurrent ecosystem variations, where open C4 grasslands abruptly transitioned to closed C3 forests within several hundreds to thousands of years. Carbon-isotopic signatures correlate most strongly with Earth’s orbital geometry (precession), and tropical sea-surface temperatures are significant secondary predictors in partial regression analyses. The scale and pace of repeated ecosystem variations at Olduvai Gorge contrast with long-held views of directional or stepwise aridification and grassland expansion in eastern Africa during the early Pleistocene and provide a local perspective on environmental hypotheses of human evolution.
Also, here’s the Supporting Information Appendix and an AGU ePoster from the same authors.
So research finds that climate change influences human development versus the inverse, Live Science appears to be an objective and informative information source, and Penn St. has honest and credible researchers, amazing stuff. I can end 2012 with a smile, I hope you all do so as well. 🙂 Just The Facts
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Nothing like pure unsubstantiated speculation presented as science.
I think I prefer to get my human origins explanations from anthropologists and not climate scientists. (Do we need another myth about climate science).
To correct some of the misinformation in this article …
About 8 million years ago, the climate started drying out for whatever reason, At this time C4 grass pollen starts to become more common in sedimentary deposits while before this time, there was almost none. These grasses evolved 24 million years ago but they did not become prevalent until dryer conditions and less rainfall overall started to give them an advantage over C3 bushes and trees.
By 6 million years ago, the first savannas developed as the climate continued drying out. Before this time, the entire planet was one big forest, There was no grasslands or savanna or deserts. It was planet of the Apes and there was 50 different species.
As the Sahara started to develop grassland at the 6 million year timeline, our story begins with the development of up-right walking.
A BBC documentary called the Origins of Us is probably the best explanation about how climate change and our physiological developments led to us. Several new things you would not have heard of in this documentary.
Search “bbc origins of us youtube” on google.
I have pictures of “Lucy” in a museum in Addis Ababa in 2006.
William McClenney says:
December 26, 2012 at 10:52 pm
“An examination of the fossil record indicates that the key junctures in hominin evolution reported nowadays at 2.6, 1.8 and 1 Ma coincide with 400 kyr eccentricity maxima, which suggests that periods with enhanced speciation and extinction events coincided with periods of maximum climate variability on high moisture levels.”
Trends, rhythms and events in Plio-Pleistocene African climate
Quaternary Science Reviews 28 (2009) 399–411
=======
Remarkable that the 400kyr cycle should exert some sort of tidal influence on our DNA without exhibiting any statistical power in the ice or sediment cores.
This sedimentary evidence for rapid and multiple transitions forest-grassland is interesting and important, though of course hardly new as several including William McClenney have pointed out. It introduces a set of important players like a Quentin Tarantino movie. CO2 in air was decreasing toward a life-threatening level. In response, C4 grasses evolved. Their arrival destabilised / de-equilibrated the climate-ecosystem phase space with the resulting flicker between two quasi-stable attractors of grassland and forest.
It is well known from Vostok and other ice-core records that “glacials” are not very stable and are punctuated by many abortive interglacials and even “micro-interglacials” of century scale duration. Thus human evolution has taken place during the predominantly glacial pleistocene characterised by acute climate fluctuation and instability. An evolutionary advantage in intelligent adaptation to climate change clearly existed (and still does today).
With the overall focus of human origin correctly on Africa, it is sometimes forgotten that hominids temporarily disapppeared from Africa. OVer the last million years or so there have been about 5 major “out of Africa” radiations. One of these established an enduring population of hominids in Asia. It is just as well, since homosubsequently went extinct in Africa. Africa was later repopulated with hominids from Asia. The genetic evidence for this is presented in “The Ancestor’s Tale” by Richard Dawkins.
Its clear why the climate and media elite dont want climate change. They feel threatened by intelligence.
It may be “pure unsubstantiated speculation presented as science” (arthur4563), yet is it one of the few such papers I have seen where believers in evolution and Darwin actually included humans and did not try to stop every bit of the evolution on the planet. Current belief seems to be that Darwin was right until “save the earth Greens” realized that Darwin was SO wrong and that nothing ever should change. And it wouldn’t if we just would stop burning fossil fuels and using up resources. No extinct species, all happily-ever-after. I was very shocked that someone actually thought humans were part of Darwin and the change is good, even though we should stop it to save the planet.
Desmond Morris first noted the thing that sets us apart in his book ‘The Naked Ape’ but made little of it. The human female is permanently receptive to the male, does not advertise when she comes in to season and can breed at any time of the year. This makes it almost impossible to be a human alpha male with a harem, you’d be on your knees, it completely restructures the social groupings.
Homo errectus survived well over a million years of climate change but the last ice age forced him to evolve or die. You have to ask yourself, what did H.heidelbergensis have that he did not? Could it simply be that without a constraining alpha male everyone got destressed, had a lot more free time and the full potential of the gene pool for evolution was opened up by pair bonding?
The cart and donkey images at the top remind me of this image:
https://docs.google.com/file/d/0B_RXGJAF_XL5ZVltNTVjMkM1WFk/edit
Any suggestions for an evolution-related quote?
phlogiston says:
December 27, 2012 at 8:42 am
The cart and donkey images at the top remind me of this image:
………………………….
Vukcevic had a good one.
http://www.vukcevic.talktalk.net/IPCC-GT1995-2011.htm
Reality check says:
December 27, 2012 at 7:38 am
“Current belief seems to be that Darwin was right until “save the earth Greens” realized that Darwin was SO wrong and that nothing ever should change. ”
Darwin actually thought that evolutionary change happens gradually; his ally Huxley had a different opinion. Today we know Huxley was right and that evolution happens by punctuated equilibrium.
The Greens still believe that Darwin was right and usually say that the rate of change we are producing overwhelms evolutionary processes. I don’t think it would be possible to explain punctuated equilibrium to them as it’s a little complicated.
For better or worse, we now adapt socially, that is, our societies adapt.
@DirkH: Excellent point!
@DirkH, reality check
Indeed the greens in question would do well to read some Steven J Gould (punctuated equilibrium).
@Gail Combs
Good one by Vuk, looks like he flipped it left-right for the hockey-stick effect; or maybe I did, I dont remember
I think reduction in atmospheric CO2 also give the grasses advantage over the trees. I will try to find it but I believe there is correlation between a reduction in atmospheric CO2 and the rise of the C4 plants. Along with the rise of the grasses we see the demise of many other plants. For example the Araucariaceae family of trees sees a dying off that is just about coincident with the rise of the grasses. Today there are only a few species of this family of tree (Norfolk Island Pine, and “Monkey Puzzle Tree” being a few popular examples) left around the world. The demise of these trees probably has more to do with atmospheric reduction of CO2 than any change in moisture. We still have places in the world where it is quite wet, but these species which once dominated the entire planet (the huge logs at Petrified Forest are examples of this family) are now nearly gone.
Crosspatch –
Thanks for your excellent summary. Your comments about artificially keeping the river flowing especially made me think – first, I remembered a big piece of Texas news from the early 2000’s. The Rio Grande failed to flow all the way to the Gulf of Mexico, mostly from overuse. There were some ridiculous attempts to dig a trench some hundreds of yards (or whatever it was) out to the sea, but that would have just let the sea flow into the river, instead of the digger’s intent…
Also, I recently saw this picture (link goes to PB):
http://tinyurl.com/c2gjkuw
Definitely one of the things that our smarts and technology has given us is the ability to overcome natural shortcomings – for example, I wear contact lenses for myopia – Anthony Watts uses a hearing aid – etc. It would be pretty hard for us to function, normally, or at all, without these things, and most likely the faulty genes or behavior (staring at lasers/too much loud music) would be weeded out, evolutionarily speaking.
Fortunately, this idea is not lost on low levels of education, and certainly comes to mind in most high school students. More commonly discussed are popular, “interesting” topics, like are we evolving away our little toe, but the overall message is there – we have, and have been practicing for some time, the ability to overcome natural selection.
Perhaps there is an ultimate control factor kicking in, and as others above have mentioned, perhaps we are evolving smaller brains, to ultimately become dumber, and “return to nature”. Time will tell, and the only certainty is that if we don’t get off earth at some point in the far distant future, we are destined to disappear. But this is far enough off to not be a concern for most likely the next several centuries, at least.
So we see it is easy to tell where humans get their tremendous ego that leads to these massive green schemes. Even a teenager understands that we have conquered nature when it comes to ourselves. We have a demonstrated ability to decide whether whole species and ecosystems live or die. I have said before that the greatest survival trait an animal can possess or evolve in the modern world is to look cute, or otherwise be attractive to humans. So while we can control ourselves, we can control life all around us, it is an easy mental step to say we can control inanimate natural processes as well. And with civil engineering and landscaping and agricultural methods, to some extent we believe we really can.
The fallacy, of course, is that none of this is true, and that we as humans maintain the illusion of control by implementing artificial controls, just like in your river scenario. Nature holds all the trump cards, and will ALWAYS have the ability to go farther than we can master. In practice this is simple escalation – it rains, so we dig a drainage pond. It doesn’t rain, so we irrigate. It floods, so we build dykes. It droughts, so we dam rivers for on-demand water. And so-on and so-forth. But we can’t stop an earthquake. We can’t control a volcano. We can’t make it rain, or stop raining – we can’t affect the weather/climate. So we are trying to. And some prefer the illusion of control, and the delusion that in this case we have it, with CO2; to the hard reality that we do not.
So an argument like Monckton’s becomes practical not just in the economic sense that he espouses. (I am talking about the argument that we should hold off on climate change measures for now, and react/adapt instead of attempting to prevent/control.) THIS is our true advantage. THIS is what we should be capitalizing on, instead of struggling so hard against it. We have evolved this tremendous intelligence that gives us the ability to adapt, to react to changes in our surroundings, to survive. Stop trying to control the world, and instead adapt ourselves to where the world is going.
Stop trying to control things, and instead adapt to where things are going.
Unfortunately, going from the first half of that sentence to the second half is the most severe mental hurdle many people will ever face, and the implications of it may been seen in every aspect of human life (e.g. controlling economic markets vs. letting them go, parents attempting to enforce decades-old ideas on their children, elderly refusing to adopt new technologies, drug users of all kinds manipulating their emotions instead of dealing with them).
Forced progressivism is equally as bad and wrong as forced regressivism or artificial controls maintaining the status quo. Time is passing, life is happening and going by, whether we want it to or not. Why should we waste ourselves swimming upstream?
Erratic environment? Are you sure the environment can be erratic?
Well, I believe things like myopia were what led to division of labor. Take a time many thousands of years ago when all males were hunters/warriors. Some males would have better eyesight and make better hunters than others. Those with poor eyesight probably weren’t able to feed as large a family or maybe fell prey to a wild animal or stepped on a snake or something. This tended to reduce the number of men with poor eyesight. Then somewhere along the line, someone realized that the guy with poor eyesight who wasn’t much of a hunter made really good spear points or was good at making fish traps or other fine work that could be done close up. We then start to see a division of labor where someone makes fish traps in exchange for fish or spear points in exchange for meat. So once we have people specializing in various things, we develop a situation where the results of the hunt are brought back and shared among the community because everyone in that community played some supporting role in obtaining it. Those who did not pull their weight or were some sort of burden to the community (say, by stealing) were exiled to the wilderness alone where they probably didn’t survive long, particularly once winter came in the temperate regions.
Someone who has some handicap that makes them less able to survive on their own might actively seek out some other skill that makes them worth having around. And some of these traits might be hereditary so that the skill is passed from father to son because the father’s poor eyesight was passed from father to son and the father is passing along a worthwhile skill. We also see that the way labor was often divided between men and women, myopia would be less of a handicap for their sort of work and we see that generally more women than men are nearsighted though in today’s world we see much more nearsightedness than we did before spectacles were invented because before that time, nearsighted individuals might not have been able to provide quite as much of their own food or maybe were more likely to suffer accidents. I would imagine that drafting of men for an army in the 1600’s would have brought out people with a wide variety of different degrees of eyesight. I would also be willing to bet that warrior clans were those where good eyesight ran in the family. Good eyesight is “expensive” to produce genetically and eyes tend to be only as good as required. If we suddenly lost the ability to make corrective lenses, we would probably see the population decline but the overall average eyesight would improve.
phlogiston says:
December 27, 2012 at 11:31 am
“@DirkH, reality check
Indeed the greens in question would do well to read some Steven J Gould (punctuated equilibrium).”
It can be observed in genetic algorithms. I often have weeks with no process, then a cluster of days with successive improvements. I observed this in logic optimization evolutions as well as in trading strategy optimizations. In both cases, I use analogons to s3xual reproduction (crossovers, introns).
I have had a question for some about why the North Pole is generally warmer than the South Pole. Could someone tell me where my understanding is incorrect or incomplete?
In simple terms: I can see one major reason, but am not sure. But first, there are two major phenomena which cause the climate of the poles. Nearness to the sun and axis of rotation. During the southern hemisphere’s summer, the earth is closer to the sun. Of course the tilt of the earth has a far greater affect on temperatures in that hemisphere than does the distance. One would think it logical for the southern hemisphere to have a warmer summer than the Northern Hemisphere. Conversely, the South Pole during winter is both tilted away from the sun while the earth is farther from the sun during its winter so it should have colder winters than the Northern Hemisphere.
All else being equal (and it isn’t), the average energy in both hemispheres should be the same, however. I’ve always thought that since the North Pole is all water and that water circulates, there would be more warmth there than in the South Pole region which is a giant land mass.
My conclusions:
1) North and South Hemispheres get the same energy from the sun over a calendar year.
2) South Hemisphere has more extremes (more energy in summer, less energy in winter than North hemisphere.
3) Land Mass in South Pole has the greatest affect on climate there, being an island which is less affected by direct contact with water circulation.
Is it much more complex than this?
Heh, now I wonder if those animal paintings on the walls of caves were an eye test for hunters. The idea being someone had to stand some distance away while someone pointed to different animals and the prospective hunter had to be able to discern which animal was which. Those who could do so accurately were accepted to become hunters and those who didn’t became weavers or some other job.
2kevin
December 26, 2012 at 10:42 pm
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Climate variability has been one of the strongest factors in Carnivore evolution.
DesertYote says:
December 27, 2012 at 2:22 pm
Climate variability has been one of the strongest factors in Carnivore evolution.
Close, however the intent of your thought is better expressed …
Prey variability has been one of the strongest factors in Carnivore evolution.
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I caution ALL readers (and writers) to remember that – unless one accepts “Evolution” as a forwardly cognizant Intelligent Designer who (simultaneously!) observes things as they actually are in the current world, correctly anticipates the future world and the future environment and “plans” genetic improvements in tens of millions of species FOR the specific and unique future that the Intelligent Designer has projected hundreds and millions of years into the future – one can only describe “evolution” as “repeated accidental and random genetic mutations that don’t immediately kill its victim nor the children of its victim
“Evolution” – as it is accepted in today’s “science” – cannot predict, adapt,defend, change, nor prevent changes in any single generations Only an Intelligent Designer can act deliberately and with forethought.
It is impossible to take these people seriously. They use “transition” as a verb.
“in which open grassland landscapes transitioned to closed forests”
Difference in temperature of the poles: Two things: altitude and proximity to open water. The South Pole is at 10,000 feet altitude and is a long way from open water. What is the temperature 10,000 feet above the North Pole?