Average human size has changed significantly over the past few million years and is strongly linked to temperature, according to a study that indicates that cooler climates have driven the evolution of larger bodies, and warmer bodies into smaller bodies.
The results of this research were published in the journal Nature, in an article that also confirms that brain size has changed dramatically, although it has not evolved at the same pace as body size.
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To reach its conclusions, the interdisciplinary team of researchers, led by the universities of Cambridge (Great Britain) and Tübingen (Germany), gathered measurements of the body and brain size of more than 300 fossils of the genus Homo found around the world. .
Combining this data with a reconstruction of the world’s regional climates over the past few million years, the researchers identified the specific climate that each fossil experienced when it was a human being, explains the British university in a note.
The study reveals that the average human body size has fluctuated over the past few million years, with larger bodies in cooler regions; a larger size is believed to act as a buffer to cooler temperatures.
A defining feature of the evolution of our gender is the tendency to increase body and brain size; Compared to previous species such as Homo habilis, we are 50% heavier – and our brains are three times larger.
The causes of these changes remain highly debated. “Our study indicates that climate – especially temperature – has been the main driver of changes in body size over the last few million years”, summarizes Professor Andrea Manica, a researcher at the Department of Zoology at the University of Cambridge, who led the study .
According to the scientist, “we can see in people living today that those living in warmer climates tend to be smaller, and those living in colder climates tend to be larger.” “We now know that the same climate influences have been at work for the last few million years.”
The researchers also looked at the effect of environmental factors on brain size in the genus Homo, but the correlations were generally weak. Brain size tended to be larger when Homo lived in habitats with less vegetation, such as open steppes and grasslands, but also in more ecologically stable areas.
Combined with archaeological data, the results suggest that the inhabitants of these habitats hunted large animals for food, a complex task that could have spurred the evolution of larger brains.
“The environment influences the size of our body much more than that of our brain,” says Manuel Will, from the University of Tübingen.
Thus, research suggests that non-environmental factors were more important than weather in driving larger brains, including the additional cognitive challenges of an increasingly complex social life, more diverse diets, and more sophisticated technology.
The authors claim that there is “strong evidence” that the size of the human body and brain continues to evolve. The human physique continues to adapt to different temperatures and, on average, older people today live in colder climates. On the other hand, our species’ brain size appears to have shrunk since the beginning of the Holocene (about 11,650 years ago).
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