As an adaptive response, the human brain is likely to shrink as the planet’s climate warms, says a new study published in the journal Brain Behavior Evolution, suggesting a link between past climate changes and a decrease in the size of the human brain.
“Given recent global warming trends, it is important to understand the impact of climate change, if any, on human brain size and, ultimately, human behavior,” wrote the cognitive scientist Jeff Morgan Stibel of the Museum of Natural History in California (United States).
We already know that climate changes are well-documented drivers of biological change. We see the effects on animals; in a warmer world, we see birds shrinking in size or small reptiles aging without time to adapt to climate change.
And the man?
Nor are we immune to these evolutionary changes. The researchers conducted an analysis of climate records and human remains from Homo specimens for 50,000 years. Stibel obtained data from 373 measurements of 298 human bones, concluding that the human brain is likely to shrink as the climate warms, a claim that could add to our understanding of how humans evolve and adapt in response to environmental stress.
“Understanding how the brain changes over time in hominids is important, but very little work has been done on this topic,” Morgan Stibel told PsyPost.org. “We know that the brain has evolved in species over the last few million years, but we know very little about other macroevolutionary trends.”
Fortunately, we have accurate measurements of what the surface temperature was at various points in Earth’s history. When comparing the brain size of these climate records (four climate records and temperature data from Dome C of the European Antarctic Ice Core Project), the brains of our ancestors shrank by more than 10% during the Holocene (about 11,700 years ago to the present), when the climate warmed.
Brain size doesn’t always equate to cognitive function, but it has a huge impact on how we look and act. “Even a small reduction in the size of the brain of existing people can affect our physiology in a way that is not fully understood,” the expert clarified.
“Changes in brain size appear to occur thousands of years after climate change, and they are particularly pronounced after the last glacial maximum, about 17,000 years ago,” explained Stibel in his work. “Whereas (acclimation) progresses over a generation and natural selection can occur over just a few successive generations, adaptation at the species level often takes many successive generations.”
The research leaves no doubt: when the climate became warmer, the average brain size became smaller than when it was colder. The study shows that human biology is driven by natural selection influenced by environmental pressures. And as the Earth begins to warm faster, it is unclear how this will affect us humans hundreds and thousands of years into the future.