An provocative question to which a positive answer could surely change the whole debate.
This article from Smithsonian Magazine examines it.
Earth’s climate has always been in a state of flux. Ever since our ancestors branched off the primate evolutionary tree millions of years ago, the planet has faced drastic swings between moist and dry periods, as well as long-lived glacial freezes and thaws. It’s clear that early humans were able to survive such changes—our existence confirms their success. But a growing number of scientists think that major climate shifts may have also forged some of the defining traits of humanity.
In particular, a few large evolutionary leaps, such as bigger brains and complex tool use, seem to coincide with significant climate change. “I think, to be fair, all we have at the moment is coincidence,” said Peter B. deMenocal of Columbia University’s Lamont-Doherty Earth Observatory. But he and other researchers are exploring several lines of evidence, from ancient teeth to seafloor sediments, to see if a more concrete link can be supported.
The data is also helping scientists sift through the possible theories for just how climate might have triggered evolutionary advances. For instance, one idea is that big leaps forward were not driven by adaptation to a specific habitat change, but by a series of frequent changes. In other words, humans evolved to live with uncertainty. Rick Potts at the Smithsonian Institution’s Human Origins Program calls this idea “variability selection”, and it’s possible at least two major evolutionary events can be linked to periods of climate instability.
“Roughly between 3 and 2.5 million years ago, the lineage of ‘Lucy’ [Australopithecus afarensis] became extinct and the first members of our own genus, Homo, appeared. The first simple stone tools also appeared with those fossils, which featured some modern traits like bigger brains,” deMenocal says. “Then, between 2 million and 1.5 million years ago, we see Homo erectus.” That bigger-brained hominin had a skeleton very much like our own, more sophisticated tools like double-bladed axes and new behaviors that led early humans out of Africa for the first time.
Both of these events happened at times when the local climate was undergoing dramatic shifts. We know, for instance, that some 3 million years ago—around the time the first Homo species appeared—Africa was switching from wooded areas to open grasslands as the climate dried out. This straightforward change in scenery may be part of why early humans evolved away from climbing and toward walking upright. But recent evidence collected from the seafloor gives an even more detailed look at the climate change during this period.
For his work, deMenocal drills into the seafloor along Africa’s coasts, where sediments that would have been long since dispersed on land remain in orderly tiers. Sediments blown offshore from Africa and Arabia have accumulated here at a rate of some 1.5 inches per 1,000 years, creating a climatic layer cake of alternating light and dark bands. During dryer periods, layers feature the dark, gritty dirt blown out to sea by ancient monsoons. During wet periods, the layers contain light amalgamations of abundant fossilized plankton.
Retrieved March 17, 2015 from http://www.smithsonianmag.com/science-nature/how-climate-change-may-have-shaped-human-evolution-180952885/?no-ist