Climate Change affecting Human Body Size and Even Brain

Climate changing our physical characteristics

Climate change has become a constant source of concern in modern society. While the majority of the attention is on the future, a new study indicates that the Earth’s climate has already influenced the growth of human bodies and even our brains over time.

The average human body size has “fluctuated significantly” during the previous one million years, according to University of Cambridge researchers, with a clear link to temperature. Colder, harsher conditions favored greater body sizes, whereas warmer climates favored smaller body sizes.

According to the research, brain size changed considerably but did not evolve in lockstep with bodily growth. Our brains are currently shrinking and may continue to shrink as a result of our over-reliance on computer technology, according to the researchers.

Bigger Bodies defense mechanism for cold

Authors from the Universities of Cambridge and Tübingen in Germany gathered data on body and brain size from more than 300 Homo genus fossils found around the world. They pinpointed the precise climate faced by each fossil while it was a living human by combining the statistics with a reconstruction of the world’s regional climates over the last one million years.

Their findings, published in the journal Nature Communications, show that human body size has changed significantly over the previous million years due to climate changes. Bigger bodies, according to the researchers, may act as a barrier against cooler temperatures since they lose less heat when their mass is vast compared to their surface area.

Our species, Homo Sapiens, first appeared in Africa some 300,000 years ago. The genus Homo, on the other hand, has been around for considerably longer and includes extinct species like Homo habilis and Homo erectus.

The pattern of increasing body and brain size is a “defining characteristic” of our genus’ history, according to the experts. Modern humans are 50 percent bulkier and have three times the brain size of older species such as Homo Habilis. Scientists, on the other hand, are still debating what causes such shifts.

Human fossils illustrating the variation
Human fossils illustrating the variation in the brain (skulls) and body size (thigh bones) during the Pleistocene period.

In a university announcement, study leader Professor Andrea Manica of Cambridge’s Department of Zoology said, “Our analysis reveals that climate change – notably temperature – has been the main driver of variations in body size for the past million years.”

Factors influencing our Brain Size

The researchers also looked at the impact of environmental influences on brain size in genus Homo but found that the link between the two is minimal. When Homo Sapiens lived in settings with less vegetation, such as open steppes and grasslands, but also more ecologically stable locations, their brains were larger.

The findings, when combined with archaeological evidence, show that individuals who lived in such habitats hunted enormous animals for food, a difficult undertaking that may have prompted the evolution of larger brains.

The study also implies that non-environmental factors, such as the extra cognitive challenges of increasingly complicated social lives, more diverse meals, and more sophisticated technologies, are more relevant than the climate in driving larger brains.

Technology Affecting our Brain

According to the researchers, there is “strong evidence” that the human body and brain sizes are continually evolving as the human body adapts to varied temperatures, with larger-bodied humans living in colder areas today. Our species‘ brain size, on the other hand, appears to have been “shrinking” since the Holocene began 11,650 years ago.

Prof. Manica believes that as people become more reliant on technology, such as outsourcing hard activities to computers, brains will continue to atrophy over the next few thousand years.

“It’s interesting to guess about what may happen to body and brain sizes in the future,” the researcher adds, “but we should be cautious about extrapolating too much from the last million years because so many factors can change.”



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