Climate change could shrink the human brain: what scientists warn about
Climate change is already having a significant impact on people's lives, changing landscapes and weather in all regions of the planet. But there are among its effects quite unexpected. For example, some scientists suggest that it may lead to a reduction in the size of the human brain.
As writes the edition of Science Alert, this conclusion was reached by cognitive scientist Morgan Staybel of the Natural History Museum in California. He studied climatic data and examined the characteristics of human remains over a period of 50,000 years. His goal was to investigate the relationship between temperature fluctuations and brain size and, consequently, human behavior.
For his work, he processed brain size data from 298 individuals of the Homo species and analyzed how they had changed over the past 50 millennia in relation to natural data on global temperature, humidity and precipitation. The correlation he found showed that during periods when the climate became warmer, the average brain size decreased markedly compared to colder periods.
Steibel was prompted to do this work by his earlier research related to brain shrinkage. The scientist wanted to understand the reasons for this trend. "We know that brains have grown in different species over the last few million years, but we know very little about other macroevolutionary trends," he said.
To reach his conclusions, Staibel processed skull size data from ten separate published sources. In all, he took 373 measurements of 298 human bones for his study. He also included body size estimates, adjusted for geographic region and sex of the individual, to estimate the size of the brain to which he belonged.
The fossils were also divided into groups based on their age. There were four groups in total - 100 years old, 5,000 years old, 10,000 years old and 15,000 years or more. This allowed the dating errors to be explained.
The scientist compared the findings with four climate records, including temperature data from the European Project for the Study of Antarctic Ice (EPICA) Dome C. This project examines ice samples, which provide fairly accurate data on the surface temperature of the planet more than 800,000 years ago.
The last glacial maximum was found to have occurred about 50,000 years ago. Because of it, average temperatures remained rather low until the end of the Late Pleistocene. The increase occurred in the Holocene and continues to this day.
Comparison of the data obtained showed a general pattern of changes in the brain size in Homo, which correlates with climate change as temperatures rise and fall. Thus, during the Holocene warming period, the average brain size decreased significantly, by just over 10.7% on average. "Changes in brain size seem to occur thousands of years after climate change, and this is especially evident after the last glacial maximum about 17,000 years later," Steibel explained the pattern he found in his paper.
The evolutionary change he identified occurred over a fairly short period of time - between 5,000 and 17,000 years. If this trend continues, it could have a negative impact on humanity's cognitive abilities.
The analysis showed that humidity and precipitation levels also affected brain growth. But periods of drought and wet periods showed little correlation on this measure.
Questions still remain about what causes changes in human brain size. The results show that climate does not explain all evolutionary changes, although it does have a significant influence. According to Steibel, ecosystem factors such as predation, indirect climate effects (vegetation, net primary productivity, etc.) and non-climatic factors like culture and technology can contribute to changes in brain size. The topic needs further, more in-depth study.
Previously OBOZREVATEL told about the discovery of DNA of a sea creature associated with climate change, hinting at a sad fate for humanity.