Climate Has Changed the Size of Our Bodies &, to Some Extent, Our Brains

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Photo: Manuel Will

A team of interdisciplinary researchers led by the University of Cambridge and the University of Tubingen have collected measurements of body and brain size of over 300 Homo fossils found worldwide. Combining this data with the reconstruction of the global regional climate over the last million years, they identified the specific climate that each fossil experienced when it was a living human.

Studies average body Human size has fluctuated significantly over the last million years, with larger bodies evolving in colder regions. It is believed that the larger the size, the more it acts as a cushioning material against low temperatures. When the mass is large compared to the surface area, less heat is lost from the object. Results will be published in the journal today Nature Communications.

Our species, Homo sapiens, emerged in Africa about 300,000 years ago. The genus Homo has been around for a long time and includes Neanderthals and other extinct related species such as Homo habilis and Homo erectus.

A distinct feature of the evolution of our genus is the tendency for body and brain size to increase. We are 50% heavier and our brains are three times larger than early species such as Homo habilis. However, the driving forces behind such changes are still highly debated.

“Our study shows that climate, especially temperature, has been a major driver of body size changes over the past million years,” said a study by the University of Cambridge’s Faculty of Zoology, which led the study. Said Professor Andrea Manika.

“Today’s people see that people in warmer climates tend to be smaller and people in colder climates tend to be larger. We see that the effects of the same climate have worked over the last million years. “”

Researchers also examined the effects of environmental factors on the size of the Homo brain, but the correlation was generally weak. Brain sizes tended to increase when homo lived in less vegetated habitats such as grasslands and grasslands, as well as in ecologically more stable areas. In combination with Archaeological data, the results suggest that people in these habitats hunted large animals for food. This is a complex task that may have driven the evolution of the larger brain.

“We have found that various factors determine brain size and body size. They are not under the same evolutionary pressure. The environment has a far greater impact on us. Body size More than the size of our brain. ” Dr. Manuel Will of the University of Tubingen, Germany, is the first author of this study.

“In more stable and open areas, the size of the brain has an indirect environmental effect. The amount of nutrients obtained from the environment enables the maintenance and growth of our large, especially energy-hungry brain. Had to be enough. “

The study also suggests that non-environmental factors were important for moving larger brains. climateThe main candidates are the increasingly complex social life, more diverse diets, and the added cognitive challenges of more sophisticated techniques.

Researchers are with the human body Brain size It keeps evolving. Human physiques are still adapted to different temperatures, and today, on average, larger people live in colder climates. The size of the brains of our species seems to have shrunk since the beginning of the Holocene (about 11,650 years ago). Increased reliance on technology, such as outsourcing complex tasks to computers, can further shrink the brain in the coming thousands of years.

“It’s fun to guess what happens to your body's brain It will grow in size in the future, but many factors can change, so care must be taken not to over-externalize based on the last million years, “says Manica.

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