No, the human brain did not shrink 3,000 years ago: research

The 12th century B.C.E., when humans were forging great empires and developing new forms of written text, may have been the time when brain size was reduced. A UNLV-led team of researchers refutes a hypothesis that is growing in popularity among the science community.

A group of scientists made headlines last year when they said that our ancestors' ability to store information in social groups decreased our need to keep large brains. The evolutionary reduction of modern human brain size was the subject of their hypothesis.

UNLV anthropologist Brian Villmoare and John Moores University scientist Mark Grabowski disagreed.

The UNLV-led team analyzed the data that the research group used to dismiss their findings in a new paper.

The appearance of Egypt's New Kingdom, the development of Chinese script, and the emergence of the Olmec are just a few of the important innovations and historical events that took place during this time.

The brain size of humans has not changed over the last 30,000 years. We can't find a reduction in brain size in modern humans over the course of time.

There are a number of keyTakeaways.

The UNLV research team questioned several of the hypotheses that De Silva and his colleagues came up with.

• The UNLV team says the rise of agriculture and complex societies occurred at different times around the globe—meaning there should be variation in timing of skull changes seen in different populations. However, DeSilva's dataset sampled only 23 crania from the timeframe critical to the brain shrinkage hypothesis and lumped together specimens from locations including England, China, Mali, and Algeria.
• The dataset is heavily skewed because more than half of the 987 skulls examined represent only the last 100 years of a 9.8-million-year span of time—and therefore don't give scientists a good idea of how much cranial size has changed over time.
• Multiple hypotheses on causes of reduction in modern human brain size need to be reassessed if human brains haven't actually changed in size since the arrival of our species.

More information: Brian Villmoare et al, Did the transition to complex societies in the Holocene drive a reduction in brain size? A reassessment of the DeSilva et al. (2021) hypothesis, Frontiers in Ecology and Evolution (2022). DOI: 10.3389/fevo.2022.963568 Journal information: Frontiers in Ecology and Evolution