Human World

Peter deMenocal: Climate change might drive human evolution

Climate change might have driven turning points in human evolution, according to an April 2012 gathering of scientists hosted by Columbia University’s Lamont-Doherty Earth Observatory (LDEO).

What’s more, scientists have within their grasp the ability to answer this question by filling gaps in the fossil record and reconstructing past climates. That’s according to LDEO paleoclimatologist Peter B. deMenocal. He told EarthSky:

One of humankind's greatest inventions: the two-sided stone cutting tool coincide with rise of genus Homo. Acheulean Biface from Saint Acheul, Amiens, Somme, France. (Wikipedia)
One of humankind’s greatest hits: the two-sided stone cutting tool coincides with rise of genus Homo. Acheulean Biface from Saint Acheul, Amiens, Somme, France.

The linkage between faunal change and climate change really has to do with a very basic observation, which is that organisms are fundamentally linked to the resource availability of a given landscape. As the energetics of the landscape, the utility of the landscape changes, the fauna have a series of options that that they can either adapt or become extinct.

The appearance of genus Homo about 2.5 million years ago and the later development of a two-sided stone blade tool set a million years later mark turning points of human evolution linked to climate, said deMenocal. He said:

We’re now beginning to place these evolutionary change points within the context of past environmental change in Africa to examine this question of whether the evolutionary changes themselves were coincident and perhaps linked to changes in the environment in East Africa.

The dry grasslands of East Africa today were once canopied woodlands, said deMenocal.

Those grasslands didn’t come into being until almost two million years ago. Actually, the first appearance of that really open dry, arid, vegetation coincided in time almost exactly with this Acheulian tool kit, this very sophisticated bi-facial rock blade.

It’s this transition toward more open conditions and more variable conditions that is thought to have been the motor behind some of the evolutionary changes that occurred at this time.

fossil skulls
‘The history of human evolution really takes place in East and South Africa several million years ago,’ said Peter deMenocal. Image credit: Smithsonian

What’s more, Homo errectus – the branch from which modern humans emerged – came out of Africa at roughly this same time two million years ago. DeMenocal added:

What really leads to new life forms emerging and new adaptations emerging comes from the challenges climate change presents. There are winner and losers to that process. There are things that go extinct and there are new organisms that pop up and become successful in a new climatic regime. It’s really climatic instability that leads to the best adaptations to a given environment, because it provides a shake-up the resources for a given environment.

The April 2012 symposium at Columbia University comes off the heals of a 2010 report by the National Research Council and a February 2012 article by deMenocal in Science magazine that examine the premise of whether climate change shaped human evolution. There simply isn’t enough evidence to firmly establish this link, but the scientific tools exist today to get answers, said deMenocal. This question has relevance even to what’s happening today, he added.

The lesson that we take home from the study of how climate change may have changed early human evolution is a recognition of the larger truth, which is actually echoed throughout the geologic record of the co-evolution of life on the planet and climate change — is that there are many, many examples of extinctions linked to events of massive environmental change.

And so if we take the biggest possible view of this, the story of life on Earth is really one that is a dance between the co-evolution of life on the planet and the physical environment, the climate. So as climate changes in the future, one has to expect, with one’s eyes open, that aspects of the living world will respond to the climate changes that are underway.

Bottom Line: In an EarthSky interview, paleoclimatologist Peter B. deMenocal spoke about how climate change might have driven turning points in human evolution. The rise of genus Homo and stone tools coincides with climate change two million years ago in East Africa. It’s too early to tell for sure, said deMenocal, but scientists have the ability today to start answering whether this link is solid.

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May 29, 2012
Human World

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