Contrary to Popular Belief, Building Cities Probably Didn’t Reduce Humanity’s Brain Size

5 mins read

According to popular and scholarly belief, the development of cities coincided with a rapid decline in the size of the human brain roughly 3,000 years ago, but new research contradicts this theory.

Your brain can shrink for a variety of reasons, including living in Antarctica, being exposed to pollution, using alcohol, and COVID-19. However, a recent analysis of data that was previously used to argue that human brain size decreased around the time when huge urban areas arose reveals that living in cities isn’t one of them, at least not 3,000 years ago.

Anthropologists have used the internal size of our ancestors’ skulls as a proxy for intellect throughout millions of years. They came to the conclusion that brain size first increased gradually, starting five million years ago with our last common ancestor with chimpanzees, before speeding up around 2 million years ago.

However, a report published last year that claimed this trend reversed in the 12th century BCE, about the time that urban living became common, attracted a lot of interest. The consequences of this have been debated extensively, but an article published in Frontiers in Ecology and Evolution questions whether it even occurred.

Although the time and reason were deemed questionable, numerous publications lately raised the possibility of a significant shrinkage in brain size. The decline was dated to 3,000 years ago by Professor Jeremy DeSilva of Dartmouth College and his co-authors using a sample of 987 skulls from museum collections. They explained the decrease by pointing to the rise of writing and other technologies that reduced the need for memory. Similarly, as cities grew, people were able to specialize more, potentially developing larger brain regions for the particular abilities they used regularly while atrophying smaller brain regions for the tasks they delegated to others.

In a statement, Dr. Brian Villmoare of the University of Nevada said, “We re-examined the dataset from DeSilva et al. and discovered that human brain size has not changed in 30,000 years, and probably not in 300,000 years.” In fact, using this dataset, we are able to say that modern humans’ brain sizes have not decreased at any point since the emergence of our species.

Despite assertions of a reduction in human brain ability stretching back more than 40 years, the material presented had some clear flaws. Writing and major cities emerged at different times throughout the world; if these developments were to blame for brain shrinkage, this would have been evident far sooner in Egypt, for instance, than in regions where even agriculture didn’t become widely practiced until much later.

Villmoare and his co-author, Dr. Mark Grabowski of Liverpool John Moore University, draw attention to the fact that DaSilva’s skulls came from a broad variety of sites without taking into account the level of civilization in those areas at the time.

In addition, they point out that although 987 seems like a sufficient sample size at first, half of the skulls date from the 20th century. The remaining 500 samples cover a time period from 9.8 million years ago, before Australopithecines, much less humans, had emerged, until the 19th century. Only 23 skulls from the 5,000–1,000 years ago timeframe were present, which is clearly insufficient for drawing broad conclusions considering how diverse any community may be.

The recent skulls in DeSilva’s database have an average size that is substantially smaller than the majority of other estimations for the modern average.

Though it might seem irrelevant, the subject of whether sophisticated cultures have caused our brains to shrink is actually quite intriguing. However, the measurement of brain power has a troubled past, with bogus figures being used to defend atrocities like slavery.

The use of criteria like skull form to justify racism has increased in recent years. Although DeSilva and the other writers may have had the best of intentions, extrapolating broad generalizations from small samples leaves room for those who have more nefarious criticisms.

Ali Esen

Istanbul University, Department of Mathematics. Interested in science and technology.

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