New research has found that climate change has altered the average body size of humans, fluctuating significantly over the last million years, according to CNN.

Researchers at the University of Cambridge in the United Kingdom and the University of Tübingen in Germany measured brain and body size of more than 300 fossils from the Homo genus or family, to which modern-day humans (Homo sapiens) belong.

They found that climate change, particularly temperature change, played a key role in changing body size for the past million years.

The researchers, who published their findings in the journal Nature Communications, found that colder, harsher climates were linked to larger bodies and warmer climates to smaller bodies.

Dr. Andrea Manica, Professor of Evolutionary Ecology, Department of Zoology, University of Cambridge, told CNN, “Larger bodies can buffer individuals from cold temperatures — the larger you are, the smaller your surface compared to your volume, so you conserve heat more efficiently.”

“This is a relationship that is found in many animals, and even among contemporary humans,” he added, “but we now know that it was a major driver behind the changes in body size over the last million years.”

The researchers noted that climate also played a key role in altering brain size. However, there has been a lot of variation in brain size that cannot be explained by environmental changes.

Dr. Manica said, “Interestingly, brain size changes were completely unrelated to temperature, so body and brain size evolved under distinct pressures. For brain size, we found that larger brains were found in stable environments — brains are expensive, so you can’t sustain them if you lack resources.”

“For early Homo, there was also a tendency to develop bigger brains in more open habitats, where our ancestors would have been required to hunt large mammals,” he added.

“Importantly, however, climate explains changes in brain size much less than it does for body size,” Dr. Manica explained. “This means that other factors such as added cognitive challenges of ever more and complex social lives, more diverse diets, and more sophisticated technology were likely the main drivers of changes in brain size.”

Dr. Manica noted, “The changes that we described have happened over thousands of years, or rather, tens of thousands of years. So a few years of climate change will do little to our bodies or brains.”

“If we managed to keep changing the climate without destroying the whole planet for a long time — we are not doing too well in that regard — then maybe, but thankfully this is an issue we don’t have to worry about for quite a while,” he added.

Considering the study findings, the team concluded that global warming is responsible for alterations in body sizes. The story first appeared on CNN.