From the University of Nebraska-Lincoln . Tom Nelson quipped earlier today that he hadn’t noticed any pygmy horses near the equator where it is warmer.
Study: Evolution of earliest horses driven by climate change
New research offers evidence of rising temperatures’ effects on body size
When Sifrhippus, the earliest known horse, first appeared in the forests of North America more than 50 million years ago, it would not have been mistaken for a Clydesdale. It weighed in at around 12 pounds — and it was destined to get much smaller over the ensuing millennia.
Sifrhippus lived during the Paleocene-Eocene Thermal Maximum, a 175,000-year interval of time some 56 million years ago in which average global temperatures rose by about 10 degrees Fahrenheit, caused by the release of vast amounts of carbon into the atmosphere and oceans.
About a third of mammal species responded with significant reduction in size during the PETM, some by as much as one-half. Sifrhippus shrank by about 30 percent to the size of a small house cat (about 8.5 pounds) in the PETM’s first 130,000 years and then rebounded to about 15 pounds in the final 45,000 years of the PETM.
Scientists have assumed that rising temperatures or high concentrations of carbon dioxide primarily caused the phenomenon in mammals during this period, and new research led by Ross Secord of the University of Nebraska-Lincoln and Jonathan Bloch of the Florida Museum of Natural History at the University of Florida in Gainesville offers new evidence of the cause-and-effect relationship between temperature and body size. Their findings also offer clues to what might happen to animals in the near future from global warming.
In a paper to be published in the Feb. 24 issue of the international journal Science, Secord, Bloch and colleagues used measurements and geochemical composition of fossil mammal teeth to document a progressive decrease in Sifrhippus‘ body size that correlates very closely to temperature change over a 130,000-year span.
Bloch, associate curator of vertebrate paleontology at the Florida Museum of Natural History, said multiple trails led to the discovery.
One was the fossils themselves, recovered from the Cabin Fork area of the southern Bighorn Basin near Worland, Wyo. Stephen Chester, then an undergraduate student at Florida, now an anthropology Ph.D. candidate at Yale and a co-author on the paper, had the task of measuring the horses’ teeth. What he found when he plotted them through time caught Bloch and Secord by surprise.
“He pointed out that the first horses in the section were much larger than those later on,” Bloch recalled. “I thought something had to be wrong, but he was right — and the pattern became more robust as we collected more fossils.”
A postdoctoral researcher in Bloch’s lab for the first year of the project, Secord performed the geochemical analysis of the oxygen isotopes in the teeth. What he found provided an even bigger surprise.
“It was absolutely startling when Ross pulled up the first oxygen isotope data,” Bloch said. “We looked at the curve and we realized that it was exactly the same pattern that we were seeing with the horse body size.
“For the first time, going back into deep time — going back tens of millions of years — we were able to show that indeed temperature was causing essentially a one-to-one shift in body size within this lineage of horse. Because it’s over a long enough time, you can argue very strongly that what you’re looking at is natural selection and evolution — that it’s actually corresponding to the shift in temperature and driving the evolution of these horses.”
Secord, who came to UNL in 2008 as an assistant professor of Earth and atmospheric sciences and curator of vertebrate paleontology at the University of Nebraska State Museum, said the finding raises important questions about how plants and animals will respond to rapid change in the not-too-distant future.
“This has implications, potentially, for what we might expect to see over the next century or two, at least with some of the climate models that are predicting that we will see warming of as much as 4 degrees Centigrade (7 degrees Fahrenheit) over the next 100 years,” he said.
Those predictions are based largely on the 40 percent increase of atmospheric carbon dioxide levels (from 280 to 392 parts per million) since the start of the Industrial Revolution in the mid-19th century.
Ornithologists, Secord said, have already started to notice that there may be a decrease in body size among birds.
“One of the issues here is that warming (during the PETM) happened much slower, over 10,000 to 20,000 years to get 10 degrees hotter, whereas now we’re expecting it to happen over a century or two,” Secord said. “So there’s a big difference in scale and one of the questions is, ‘Are we going to see the same kind of response?’ Are animals going to be able to keep up and readjust their body sizes over the next couple of centuries?”
Increased temperatures are not the only change animals will have to adapt to, Secord said. Greenhouse experiments show that increased atmospheric carbon dioxide lowers the nutritional content of plants, which he said could have been a secondary driver of dwarfism during the PETM.
Other co-authors on the paper are Doug M. Boyer of Brooklyn College, Aaron R. Wood of the Florida Museum of Natural History, Scott L. Wing of the Smithsonian National Museum of Natural History, Mary J. Kraus of the University of Colorado-Boulder, Francesca A. McInerny of Northwestern University, and John Krigbaum of the University of Florida.
The research was funded by grants from the National Science Foundation, with additional support from UNL.
This reminds me of this video…
Enjoy it.
Grass didn’t even evolve until 25 to 30 million years later. What was the cat-sized horse eating.
“Their findings also offer clues to what might happen to animals in the near future from global warming.”
Clues to what might happen? Did I read that right? Of course I did. A clue is a snippet. A tidbit of information. A clue to something that “might” happen is a snippet of infinitesimally small proportions, which just as likely “might” point to something else. In the near future. How far? Five minutes? Five Hundred Years? Might, squared. In other words, WTFK? Yes, who, indeed. Another Meme-Club member (inserts CC assertion here). I’ve given up trying to figure out what kind of world these people live in.
**Scientists have assumed that rising temperatures or high concentrations of carbon dioxide primarily caused the phenomenon in mammals during this period**
And there you have post-modern environmental science described in a nutshell.
http://www.archive.org/details/our_mr_sun
try our new video/audio player ? (beta!)
From the description in Rick Prelinger’s Field Guide to Sponsored Films:
Popular scientific film directed by Frank Capra that launched the Bell System Science series. Combining animation and live action, Our Mr. Sun uses a scientist-writer team to present information about the sun and its importance to humankind. NOTE: Produced in Technicolor, the film was originally telecast in 1956 and 1957 to 9 million homes; some 600 16mm prints were distributed to schools and community organizations through the Bell Telephone System film libraries.
I do enjoy the sci-fi of the past. I’m always astounded by what people come up with to descibe previous times; but moreso with what gets passed off as if it’s fact.
What an incredible collection of debunked nonsense, vague half-truths, and all out delusional speculation.
I damn near fell out of my chair when I read:
“Sifrhippus lived during the Paleocene-Eocene Thermal Maximum, a 175,000-year interval of time some 56 million years ago in which average global temperatures rose by about 10 degrees Fahrenheit, caused by the release of vast amounts of carbon into the atmosphere and oceans.”
These propagandists don’t bother to mention that most of NA was covered by dense woodland, not exactly the best environment for a Clydesdale. Sheesh!
Horses were extinct in the Americas until the Spaniards showed up.
Perhaps they shrank so much they dissapeared.
What a target rich source.
One could better assert that paleo-ponies respond to changes in oxygen isotope ratios. (More likely changes in their ecological niche, but that doesn’t get grant money.)
With a “one-to-one shift in body size” and a “warming of as much as 4 degrees Centigrade” inverse relationship, a hundred years from now race horses will be a quarter what they are currently. Unfortunately, that ecological niche is filled by greyhounds.
Even the least of us will be able to “ride tall in the saddle,” as they used to say about John Wayne.
I’d better quit.
Bill,
If memory serves – I’m feeling to lazy to struggle over to the Wikipedia – the early odd toed ungulates evolved in a forest environment and gradually lost their toes as they moved out onto the newly evolving savannah.
W^3
What will happen? Probably the same thing that happened when 3 ices ages saw the temperature go up and down even more dramatically that during ther 130,000 years: nothing.
I presume they have some proof from these teeth that the CO2 rise preceded the temperature rise by a few years, not followed it by 800 as happens the rest of the time.
This is a fine example of turning otherwise interesting and ordinary research into a nail-biting shriller.
Work it out, dudes. When the African elephant migrated to South Asia, the shock of the greatly intensified heat shrank the big fellas right down to their sperm and ova. No?
What if what ever it was that caused the temperature to rise also caused mammals to shrink. Since nobody’s looking past their nose we’ll never know.
Great video Nerd. I highly recommend it. Very funny.
w.w.wygart says:
February 23, 2012 at 5:34 pm
Bill,
If memory serves – I’m feeling to lazy to struggle over to the Wikipedia – the early odd toed ungulates evolved in a forest environment and gradually lost their toes as they moved out onto the newly evolving savannah.
W^3
—————————
Savannah didn’t really exist until about 8 million years ago. From 55 Mya until 8 Mya, the planet was mostly forested except for Antarctica (starting about 40 Mya) and the northern parts of Greenland (starting about 10 Mya).
So, these are not the same horses with the same digestive system that horses have today. Just as a further example, there were 50 different species of Apes on the planet 10 Mya (one of which lead to us and gorillas and chimpanzees – not sure about the other Apes).
This is exciting!
So if humans also shrink to half size that would be about one quarter our mass.
Viola population problem solved, we could then crowd at least 28 billion people on our planet.
Another benefit of global warming. /sarc
You are probably correct about the grass. Until then the food supply was limited and size varied with the level of food competition. I had a botany professor years ago who pointed out that there are a lot of silica edged grasses out there that nothing can really eat. He wondered what the large buffet was being set for, hypothesizing that eventually some successful species would figure out how to tap this huge food supply.
I am wary of their temperature correlation with size as most of our largest mammals are from warm regions. Duh.
It may just be my faulty memory, but weren’t the dinosaurs inhabitants of a rather warm, lush planet? And there were some fairly GIANT species.
Of course, their assumptions about CO2 are simply them spouting propaganda = the money phrase = please give us more funding.
Bill Illis says:
February 23, 2012 at 5:05 pm
Grass didn’t even evolve until 25 to 30 million years later. What was the cat-sized horse eating.
=================================================
LOL…..Bill you’re right
They were eating woody vegetation, fruits, roots, etc
The move to grasses made them smaller
….grass is harder to digest
But I guess they can blame global warming or higher CO2 levels for the evolution of grasses…
..Which would be more or less correct
Only that it was the evolution of grasses, and the fact that they are more efficient at reducing CO2 levels, that have brought CO2 levels so low now that it’s limiting
We’re only going to get smaller if we forget how to farm….
I thought the eocene saw the advent of the first plus-sized herbivorous mammals like the Coryphodon , Uintatherium and the Arsinoitherium along with carnivorous critters like the Mesonyx and Hyaenodon . Nevermind the presence of the avian gastornis giganteus which was probably a carnivore as well ?
With many heavy animals competing with them for for the large herbivore ecological niche and predators becoming heavier , losing mass and gaining agility would become a survival plus for the Sifrhippus . Not that we`ll ever know for sure because of gaps in the fossil record but food supply/competition and types of predatory animals are overwhelming drivers for size in either direction , and with the exception of rapid onset glaciation periods and it`s possible correlation with extinction events for megafauna at high latitudes ( snow/ice too thick for megafauna to survive in/on ? ) milder temperatures would seem to have little effect .
Also , the ability to store fat and increasing density of insulating fur are far more likely responses within species to cooling conditions and the loss of those abilities/traits during warming conditions than size but these are hard things to determine from fossil records so You need to look at modern equivalents .
If You compare two closely related modern animals that fill the same eco-niche , i.e. Grévy’s zebra and the Mongolian horse , they live in entirely different climates temperature-wise but very similar food supply , namely semi-arid grassland and are about the same size .
All in all it looks to Me as if some paleontologists struggling for funding have been forced to go to the global warming money trough to feed their research as in this age of post-normal science there seems to be no money availible for real research unless it supports the meme .
P.S.( If any paleontologists have theories/data on how the fauna of the eocene interacted range/ timescale I would love to see any links to it , I`ve always been fascinated with the post-dinosaur megafauna but it seems to be quite hard to find good sites covering it )
So, if the study says that a third of mammals got smaller during this period… what happened to the other two-thirds of mammals? Did they stay the same? Did they get bigger?
I mean, I read that line and it makes me think “most mammals during this period did NOT respond that way to the warmer climate.” Is that crazy of me?
It must be pretty cold where they raise those big Arabians.
Sifrhippus lived during the Paleocene-Eocene Thermal Maximum, a 175,000-year interval of time some 56 million years ago in which average global temperatures rose by about 10 degrees Fahrenheit, caused by the release of vast amounts of carbon into the atmosphere and oceans.
======================
okeee…..dokeee
http://www.climateconversation.wordshine.co.nz/docs/pics/co2_temp_last_600m_years.gif
This is a FWIW posting in case someone is interested.
Horses that landed on Sable Island (off Nova Scotia), either brought there intentionally or shipwrecked, have evolved smaller. But whether it is the chilly location or the limited food supply that caused the recessive evolution I can’t say, but my money is on the food supply mostly. Someone sentenced to Siberia noticed that it was the big people who died first, because the food ration was the same for everybody and bigger people just needed more food.
Well, this PROVES my theory that the rest of you have laughed at…
As temperatures rise, humans, as well as horses, get smaller. The obvious proof that this is causation and not simple correlation is seen in the range of human species inhabitants of various climates.
As you all will respectfully take note, the Inuit in the frigid north are HUGE, while their counterparts in the slightly warmer Rwanda region are horribly diminutive. Thousands of years of gradual climate change have caused this catastrophic anomaly, which we must study in depth to understand.
If we only had some more grant money…..
Over human history…. man was how big 10,000years ago? Man is, on average, how big now with what difference in global mean temperature?
Inuit in the very cold north are how big? Tutsi in the very warm equator, are….how big?
Perhaps temperature is not necessarily a good metric for what drives size?