The human brain shrunk 3,000 years ago? Long accepted theory challenged by University of Nevada anthropology team

Did the 12th century BCE—a time when humans forged great empires and developed new forms of written text—coincide with an evolutionary reduction in brain size? Think again, says a team of researchers led by UNLV who refute a hypothesis that is increasingly popular among the scientific community.

Last year, a group of scientists made headlines by concluded that the human brain has shrunk during the transition to modern urban societies around 3,000 years ago because, they said, our ancestors’ ability to store information outdoors in social groups diminished our need to maintain large brains. Their hypothesis, which explored decades-old ideas about the evolutionary reduction in size of the modern human brain, was based on human fossils and comparison with evolutionary patterns seen in ant colonies.

Not so fast, said the UNLV anthropologist Brian Vilmoare and scientist from Liverpool John Moores University Mark Grabowski.

In a new article published last week in Frontiers in Ecology and Evolutionthe UNLV-led team analyzed the dataset used by the research group for last year’s study and rejected its findings.

“We were struck by the implications of a substantial reduction in the size of the modern human brain around 3,000 years ago, at a time of many important innovations and historical events – the appearance of the Egyptian New Kingdom, the development of Chinese writing, the Trojan War, and the emergence of the Olmec civilization, among many others,” said Villmoare.

“We re-examined the DeSilva et al. dataset and found that human brain size hasn’t changed for 30,000 years, and probably not for 300,000 years,” Villmoare said. “In fact, based on this dataset, we cannot identify any reduction in brain size in modern humans over any given period since the origins of our species.”

Key points to remember

The UNLV research team questioned many of the assumptions made by DeSilva et. al gleaned from a dataset of nearly 1,000 ancient human fossils and museum specimens, including:

  • The UNLV team says the rise of agriculture and complex societies occurred at different times around the world, meaning there should be variations in the timing of observed skull changes. in different populations. However, DeSilva’s dataset only sampled 23 skulls from the critical period for the shrinking brain hypothesis and pooled specimens from places such as England, China, Mali and Russia. ‘Algeria.
  • The dataset is heavily biased because more than half of the 987 skulls examined represent only the last 100 years of a 9.8 million year period – and therefore do not give scientists a good idea of ​​the change in skull size over time. .
  • Multiple hypotheses about what causes the modern human brain to shrink in size need to be re-evaluated if the human brain has not actually changed in size since the arrival of our species.

Read the original article here

Sharon D. Cole