Climate change has shaped our bodies and brains says new research

The research from Cambridge University has shown climate change has altered the size of our brains Credit: PA Images

Climate has changed the size of human bodies and, to some extent, human brains,research suggests.

The average body size has fluctuated over the last million years and is strongly linked to temperature, according to a new study.

Colder, harsher climates drove the evolution of larger body sizes, while warmer climates led to smaller bodies. And while brain size has also changed dramatically, it did not evolve in tandem with body size, researchers found.

The study, led by the Universities of Cambridge and Tubingen, gathered measurements of body and brain size for more than 300 fossils from the genus Homo found across the globe.

Climate has changed the size of human bodies research suggests

Experts pinpointed the specific climate experienced by each fossil when it was a living human by combining this data with a reconstruction of the world's regional climates over the last million years.

Our species, Homo sapiens, emerged around 300,000 years ago in Africa. But the genus Homo has existed for much longer, and includes the Neanderthals and other extinct, related species such as Homo habilis and Homo erectus.

A defining trait of the evolution of our genus is a trend of increasing bodyand brain size. Compared to earlier species such as Homo habilis, humans are 50% heavier and our brains are three times larger.

Professor Andrea Manica, a researcher in the University of Cambridge's department of zoology, who led the study, said: "Our study indicates that climate - particularly temperature - has been the main driver of changes in body size for the past million years."

The researchers also found that brain size tended to be larger when Homo was living in habitats with less vegetation, like open steppes and grasslands, but also in ecologically more stable areas.

In combination with archaeological data, the results suggest those living in these habitats hunted large animals as food - a complex task that might havedriven the evolution of larger brains.The research also indicates that non-environmental factors were more important for driving larger brains than climate, prime candidates being the added cognitive challenges of increasingly complex social lives, more diverse diets, and more sophisticated technology.

Researchers say the human physique is still adapting to different temperatures,with on average larger-bodied people living in colder climates today.

Brain size in our species appears to have been shrinking since the beginning of the Holocene (around 11,650 years ago).

The increasing dependence on technology, such as an outsourcing of complex tasks to computers, may cause brains to shrink even more over the next few thousand years, researchers suggest.

The research, published in Nature Communications, was funded by the EuropeanResearch Council and the Antarctic Science Platform.