Evolutionary Study Shows Human Bodies Were Partially Shaped By Climate Change 

As humans evolved, it’s become common knowledge that our body’s and brain’s have both increased in size as we developed into the Homo Sapiens we are today. The original Homo genus emerged about 300,000 years ago, and today we are much larger and have a brain three times as big as our human ancestors who lived a million years ago. 

Scientists have long debated why humans evolved the way that they did. There’s a multitude of potential explanations for why our bodies and minds grew into what they are today, but one of the newer possibilities has to do with climate change, and the role it’s played in our evolution overall. 

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A research team led by Cambridge University and Tübingen University in Germany have combined data on more than 300 human fossils from the Homo genus alongside climate models to establish a direct connection between the Earth’s climate and our evolutionary journey.

The study, published in Nature Communications, explained “what temperature, precipitation and other climate conditions each of the fossils, spanning the last million years, would have experienced when it was a living human. We found a strong link between temperature and body size, showing that climate was a key driver of body size during that period.”

The colder it gets, the bigger the humans are. If you’re bigger, you have a bigger body – you are producing more heat but losing relatively less because your surface is not expanding at the same rate,” said Dr. Manuel Will, a Tübingen University researcher and author on the study.

“It’s not completely surprising, but it’s interesting to see that in this respect our evolution isn’t that different from other mammals. We face similar problems when it comes to gaining and losing heat, so we seem to have evolved in similar ways,” said Dr. Nick Longrich.

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The study also linked changes in climate to brain size among the Homo genus species, however, it found that the environment has a much greater impact on body size than brain size. 

“This phenomenon shows that body and brain size are under different selective pressures. This study really manages to detangle the fact that both brain and body size are increasing, but increasing for very different reasons.”

“The more stable [the climate] is, the larger brains are. You need a lot of energy to maintain a big brain – in stable environments, you find more stable food, so you likely have sufficient nutrition to give you that energy,” said Dr. Will.

Dr. Will also pointed out that evolution is ongoing, “but there are different drivers now to a million years ago. The past gives us clues about the future; we can learn from it. But we cannot simply extrapolate from it. While we are currently seeing that the climate is getting warmer, we cannot assume that our bodies will get smaller as a result.”