Rising Temperatures Decreasing the Human Brain Size: Climate Connection Melting Minds

July 4, 2023
2 mins read
Source: Human Brain Size

Climate change has emerged as a potential factor influencing the evolution of human brain size, according to a recent study by cognitive scientist Jeff Morgan Stibel from the Natural History Museum in California. By examining climate records and human remains spanning 50,000 years, Stibel’s research offers valuable insights into the ways humans develop and adapt to environmental stress.

Unraveling the Impact of Climate Change on Brain Size:

Stibel’s investigation involved analyzing 298 specimens from the past 50,000 years alongside natural records of global temperature, humidity, and rainfall. The research revealed a significant reduction in average brain size during periods of warmer climates compared to cooler ones. 

Examining Macroevolutionary Trends:

Stibel expresses his disappointment at the lack of research on the broader macroevolutionary trends in brain size. While acknowledging the growth of the brain across species over the past few million years, he highlights the need for a deeper understanding of other evolutionary patterns that remain unexplored.

Methodology: Unveiling the Insights:

To gather data, Stibel collected information on skull sizes from 10 published sources, resulting in 373 measurements taken from 298 human bones spanning 50,000 years. Estimates of body size were included to accurately estimate brain sizes while accounting for geographical region and gender.

Periods of Climate Fluctuation:

Over the past 50,000 years, the Earth has experienced various climate fluctuations. Amongst them, the Last Glacial Maximum, is characterized by consistently colder temperatures until the end of the Late Pleistocene. The subsequent Holocene period witnessed rising average temperatures, leading up to the present day. Stibel’s analysis revealed a consistent pattern of changing brain size in Homo, correlated with fluctuations in climate as temperatures rose and fell.

Evolutionary Response: Brain Size Changes:

The analysis indicated that brain size changes tend to occur thousands of years after climate changes, suggesting that species-level adaptation often requires multiple generations. This evolutionary pattern occurred within a relatively brief period of 5,000 to 17,000 years, raising concerns about the potential impact of ongoing global warming on human cognition.

Beyond Climate: Factors Influencing Brain Size:

While climate plays a significant role in brain size evolution, Stibel acknowledges that other factors may contribute to the observed variations. Ecosystem elements, indirect climate effects like vegetation and net primary production, as well as non-climate factors such as culture and technology, could also influence changes in brain size.

Implications for the Future:

Stibel’s study emphasizes the need to comprehend the effects of climate change on human physiology, particularly brain size. Even a slight reduction in brain size among contemporary humans could have significant yet incompletely understood physiological implications. The findings demand continued research to determine the specific impacts of climate change on human physiology. Be it directly through temperature changes or indirectly through other elements of a changing environment.


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The Bottom Line:

The study by Jeff Morgan Stibel contributes to our understanding of the complex relationship between climate change and human brain size evolution. By uncovering the correlation between climate fluctuations and changes in brain size, this research highlights the potential impacts of ongoing global warming on human cognition. As we strive to comprehend the intricacies of the human brain, further investigations are warranted to explore the various factors driving brain size variations and their evolutionary implications.

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