HUMAN EVOLUTION: Climate change may have helped shape human evolution, according to a new study.
Image: Flickr/William Warby
An ancient lake whose shores vacillated between lush forests and dry savannahs shows how the changing climate may have shaped humanity's dawn in eastern Africa, according to new research.
Scientists studying organic remains dating back 2 million years in Olduvai Gorge in Tanzania tracked how plant life adapted to the regional climate as it shifted from regular monsoons to scorching dry spells. The researchers published their findings last week in the Proceedings of the National Academy of Sciences.
The gorge was home to some of humanity's earliest hominid ancestors, and the surrounding landscape provides some of the best glimpses of the conditions they lived in from fossil remains, tools, artifacts and plant residues.
"It's an unusual and almost extreme situation," said Gail Ashley a co-author and a professor of earth and planetary sciences at Rutgers University. "[The Olduvai Gorge is] like a perfect environment because it was a closed basin and it filled up with sediment, and those sediments recorded everything around it, just like a book."
It was in these sediments that Ashley and her collaborators found waxes from prehistoric plants and algae, collected in samples over a decade from Olduvai. The team examined residues from 2 million years ago spanning a 200,000-year time frame, around the dawn of Homo erectus.
Clayton Magill, a geochemistry graduate student at Penn State University and a co-author, explained that by measuring isotopes in these waxes, the team painted a picture of what kinds of plants grew in the gorge and what environments they lived in.
"With carbon, we can delineate between grasses and trees," Magill said, noting that different plants have different carbon signatures. Hydrogen isotopes, on the other hand, measure aridity. "Heavier [hydrogen] isotopes are associated with drier conditions," he said. Water with lighter hydrogen isotopes tends to evaporate faster, so plants end up accumulating heavier hydrogen when the ground dries up.
How brain development connects with climate
From these measurements, the researchers traced what kinds of plants grew in the gorge over time and compared them with how the climate changed, constructing a continuous record of plant and water fluctuations. "What we find is that the period between 2 million and 1.8 million years ago is associated with extreme environmental variability," Magill said.
Grasslands gave way to woody forests and back again while water levels in the gorge rose and fell, often very quickly by geological time scales. "There was evidence that there was contraction and expansion over time," said Katherine Freeman, a co-author and a geosciences professor at Penn State. "What we show is a repeated transition from the driest to the wettest on the scale of a few thousand years."
Though not as dramatic as a towering black monolith, these changes may have spurred human evolution by forcing early hominids to adapt to a rapidly changing climate, driving them to develop new strategies to hunt, gather and survive with changes in food and fresh water. "That's where the connection has been; the development of the brain, food gathering, might have been triggered by the continually changing climate," Ashley said. These changes also created selection pressures in other species like birds and reptiles.
"Our findings are consistent with variability as a driver of human evolution," Freeman said. "Rather than a slow and steady change, what we see is a pretty intense variability." This challenges views that hold that a slowly drying continent forced early hominids to evolve and disperse.
Does this have any implications for modern climate changes? It may to an extent. "The speed at which modern climate is changing is fairly unique," Magill said. "We're not really quite sure what's going to happen."
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23 Comments
Add CommentWe still have the big animal migrations in Africa. Seasonally grazing animals follow the availability of food, and predators follow the grazing animals. Even some modern African herders follow their cattle and goats that follow the food source. Why did early humans not follow the vegetation and availability of food and evolve instead?
Reply | Report Abuse | Link to this@Fanandala, you are talking about very different time frames. As new ecological niches appeared, Savannah replacing jungle, organisms adapted to those new environments. The formation of the Himalayas caused the climate of East Africa (east of the great rift valley) to become drier. Our ancestors adapted to that new environment. The ancestors of modern chimps and bonobos remained west of the great rift valley and therefore did not experience the same climate change. Also, we are always evolving, adapting to the environment, it's not a matter of choosing to do one or the other.
Reply | Report Abuse | Link to thisYeah, larger brains required more protein. Plus that monolith wouldn't let them change channels and all the adolescents would watch were music videos.
Reply | Report Abuse | Link to thisLet us hope that climate change now will move people away from obesity and SUVs. Gonna be hard to get rid of the music videos, though. They all have the same format, too.
Re: "The speed at which modern climate is changing is fairly unique," Magill said. "We're not really quite sure what's going to happen."
Reply | Report Abuse | Link to thisThat would seem to be one of the more honest statements in the current debate.
Providing that you read "fairly unique" to be rapid and man made. My read on the statement is lip service to the climate change powers that funded their research. Don't want to bite the hand that feeds you.
Reply | Report Abuse | Link to thisWhy do I say that? I had to do it to get funds for a research project years ago. Unless it was tied to climate change in some fashion no one would fund it. Once the climate change angle was included funds were magically available from several government and corporate sources.
Funny how it works.
@Shoshin, prove it or prove yourself a liar, again.
Reply | Report Abuse | Link to thisWhat is about the US that causes people to be so antipathetic to climate change theory, evolutionary theory and other scientific thinking? Is it to do with the educational system? Or is there some specific sociological influence at work?
Reply | Report Abuse | Link to thisJust a humble suggestion that we (1) avoid ad hominem remarks, (2) avoid attributing ulterior motives (3) avoid questioning the education level and intelligence of those with whom we differ. it would vastly improve the level of debate.
Reply | Report Abuse | Link to thisJust a humble suggestion that we (1) avoid ad hominem remarks, (2) avoid attributing ulterior motives (3) avoid questioning the education level and intelligence of those with whom we differ. it would vastly improve the level of debate.
Reply | Report Abuse | Link to thisShoshin (comment 5),
Reply | Report Abuse | Link to thisWe would seem to be on the same page.
If the information available to me is correct, Ted Turner publicly stated his wish to see a 90% reduction in human population. He also donated a billion dollars to the U.N. which would seem to be one of the major sources of "agw" funding. Does that make me a conspiracy theorist? It does according to some of the responses to that comment in another venue.
jnturnbull (comment 7),
Reply | Report Abuse | Link to thisRegarding your inquiry concerning alleged "agw," perhaps the following quote will be of some help:
"It's understandable that many people have questions about climate change; the bright minds at NASA certainly do. In fact, they've listed the uncertainties on their website. Scientists don't understand long-term changes in the radiant energy of the sun. They don't understand how aerosols, dust, smoke and soot interact with climate, in some cases warming the atmosphere, in some cases cooling it. Clouds have an enormous impact on climate, but as NASA humbly admits, "current climate models do not represent cloud physics well." We don't understand ocean currents, or where the moisture will or will not fall on a warmer planet, or how much the seas might rise. About half the carbon we belch into the air each year is removed by natural processes, but we don't understand them. We don't understand, we don't understand, we don't understand.
Misplaced Curiosity
http://www.huffingtonpost.com/craig-bowron/misplaced-curiosity_b_2259346.html
If the subject of this web page were not limited to "agw," it would also be my pleasure to provide you some food for thought on the topic of evolutionism and why there might also be room for doubt.
Maybe I have the wrong NASA. Seaching for "climate change" on my NSA web site provides a quite differnet impression. Here is a small quote: "The current warming trend is of particular significance because most of it is very likely human-induced and proceeding at a rate that is unprecedented in the past 1,300 years."
Reply | Report Abuse | Link to thisSorry about the typos. But I seem to have quite a different web site for NASA from Bill_Crofut. I don't recognise the earlier comments about NASA's views on climate change. HELP!
Reply | Report Abuse | Link to thisWhat is puzzling to me is that I find so much comment in the US seems to be based on the idea that science claims certainty. No self respecting scientist ever claims anything more than striving for the best approximation available. Of course climate models are not exact. But they are the best we have got so far. I don't understand why they are dismissed as fraudulent or even politically motivated.
Heard you the first time and you are right.
Reply | Report Abuse | Link to thisjnturnbull The problem seems to be that, although the climate models may be 'the best we have got so far', they are not reliable and fail to predict with any consistency. Certainly not anything you would want to base national and international economic decisions on, or gamble trillions of dollars that they could be, but may not be, right.
Reply | Report Abuse | Link to thisI have a lot of experience of mathematical modelling and agree that one has to question the robustness of specific models. But I know very little about climate science and do rely on other experts. An earlier contributor seemed to be saying that NASA was very sceptical about the current consensus. This surprised me and I checked their web site - http://search.nasa.gov/search/search.jsp?nasaInclude=climate+change
Reply | Report Abuse | Link to thisIt seemed to me that NASA IS very concerned about the potential threats posed by climate change rather than dismissing it.
But I agree that we do have to look hard at the economic trade offs. But there is a political dimension. We in the West have had a lot of benefit from fossil fuels. But the damage we may be causing affects the whole world.
jnturnbull (comments 12 and 13),
Reply | Report Abuse | Link to thisThe url provided in my comment allowing you to verify the posted quote is not a NASA web page; it's Huffington Post.
A number of scientists, in my research experience, have stated nothing in science is ever proved. The quote you provided in comment 12 seems, to me, to fly in the face of the wisdom you provided in comment 13.
Maybe there is a misunderstanding between us. I had thought that in quoting from the medical doctor's blog you were expressing doubts about climate change as such. I often hear such doubts in the US. That surprised me as the change is a clearly observable and measurable phenomenon; vide the NASA web site for the data.
Reply | Report Abuse | Link to thisBut of course we can agree that there are uncertainties in mathematical models of the climate - and there always will be. Uncertainties exist in the modelling of cancer epidemiology, but we still have deal with the causes and effects of the disease.
"If the information available to me is correct, Ted Turner publicly stated his wish to see a 90% reduction in human population." >> You mean, it was public, and you couldn't find a direct quote?
Reply | Report Abuse | Link to thisMore innuendo, slyly suggested ulterior motives, as in "Protocols of the Elder Scientists of the UN". Your burden of proof, Sir.
jnturnbull,
Reply | Report Abuse | Link to thisIt's a minor point, but Huff Post is not a medical doctor's blog. It's rather, similar in construct and purpose to this web page. That aside, it's not at all clear to me that we're in a period of global warming; maybe so, maybe not, but not on my authority:
"...[S]uperconductors and plasmas of nuclear particles...are hard to understand in much the same way Earth’s climate is: the laws governing their constituents are perfectly well-known, but there are just so damned many constituents."
http://blogs.scientificamerican.com/critical-opalescence/2012/12/18/physicists-find-a-backdoor-way-to-do-experiments-on-exotic-gravitational-physics/?WT_mc_id=SA_CAT_physics_20121221
My skepticism is based on the assertion that alleged global warming is anthropogenic. Ted Turner has publicly stated support for population control as a solution to global warming:
http://www.youtube.com/watch?v=KMd0mGlKDEw
According to one source, Turner also donated 1 billion dollars to the U.N.:
http://edition.cnn.com/US/9709/18/turner.gift/
According to another source, the U.N./IPPC is a major funding source for global warming research (and with a rather checkered history):
http://cnsnews.com/news/article/us-taxpayers-cover-nearly-half-cost-un-s-global-warming-panel
Craig Bowron is a medical doctor.
Reply | Report Abuse | Link to thisjnturnbull,
Reply | Report Abuse | Link to thisOops! Please accept my apology.
My theory re 'creationism' is this:
Reply | Report Abuse | Link to thisBiologically, we humans are still pack animals, and therefore instinctively averse to question the 'leader'-so, why rock the boat and question 'the Boss'?
Our neotenous (that is, eternally 'childish',frozen-in-time brains have allowed us to be playful and inventive, right into our old age, unlike those other chimps that didn't learn 'proper' talking and walking ; and so it came that we could develop all those rather strange habits of 'Civilization'!
Thanks to our love of 'letters', we also like to devote a lot of time to 'observe The Scripture', and particularly love to revel in dreams about both past and future; and this is right where religion comes in handy: as a sort of 'afterlife insurance scheme', concocted by our own, still rather childlike chimpish brains.
Thank God, it's elementary, and as evolutionary as anything!