Did human brains shrink 3,000 years ago, downsizing by an amount equal to around four ping-pong balls?
A controversial study last year proposed this idea, based on human fossils and a comparison to evolutionary patterns in ant colonies.
But University of Las Vegas, Nevada researchers reviewed the study and concluded that not only did human brains NOT shrink 3,000 years ago at the dawn of modern societies, but human brains are unlikely to have shrunk in the last 300,000 years.
UNLV anthropologist Brian Villmoare analysed the dataset that the research group from last year’s study used and dismissed their findings.
Villmoare said, “We were struck by the implications of a substantial reduction in modern human brain size at roughly 3,000 years ago, during an era of many important innovations and historical events — the appearance of Egypt's New Kingdom, the development of Chinese script, the Trojan War, and the emergence of the Olmec civilization, among many others.”
“We re-examined the dataset from DeSilva et al. and found that human brain size has not changed in 30,000 years, and probably not in 300,000 years.
“In fact, based on this dataset, we can identify no reduction in brain size in modern humans over any time-period since the origins of our species.”
The UNLV research team questioned several of the hypotheses in the previous study, base don dataset of nearly 1,000 early human fossil and museum specimens.
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.
The researchers say that DeSilva’s dataset sampled only 23 crania from the timeframe critical to the brain shrinkage hypothesis.
The study also lumped together specimens from locations including England, China, Mali, and Algeria.
The researchers say that the previous study 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.
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