Neanderthal populations were sparsely distrubuted. (Image: American Museum of Natural History)

For much of their 400,000 year history, Neanderthals were few and far between, a new analysis of genetic material from several of the extinct, ancient humans now suggests.

It’s difficult to put a number on the population of a species based on DNA alone, but less than a few hundred thousand of the archaic humans roamed Europe and Asia at any one time, says Adrian Briggs, an evolutionary geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig. “There never were million and millions of Neanderthals,” he told New Scientist.

That conclusion isn’t exactly Earth-shattering. Archaeological digs suggest that Neanderthals hardly lived in megacities, and the mitochondrial genome sequence from one individual found in Croatia also hints at low population sizes.


But the new findings represent the most detailed look at Neanderthal genetic diversity yet published.

Low diversity

What is most obvious is how little genetic heterogeneity they possessed. The mitochondrial genomes of six Neanderthals recovered in Spain, Croatia, Germany and Russia differ at only 55 locations out of more than 16,000 letters. This represents three times less mitochondrial diversity than modern humans possess.

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Because of this low diversity, Briggs’ team infers that Neanderthal populations must have been relatively small. “Populations with much larger sizes carry more genetic diversity, you have more individuals and more mutations,” he says.

The researchers analysed bone samples that, by and large, came during the twilight of the Neanderthal’s reign around 40,000 years ago. Neanderthals probably went extinct somewhere between 24,000 and 28,000 years ago.

It’s possible that Briggs’ team has taken a genetic snapshot of a species on the verge of extinction, however other genetic clues indicate that Neanderthal populations stayed low for much of their history, he says.

Highs and lows

Neanderthal mitochondria were far more likely than humans or chimpanzees to contain potentially harmful mutations in mitochondrial genes that changed the shape of proteins, Brigg’s team found. Since these mutations incur an evolutionary cost, they will eventually be weeded out. But this process occurs very slowly in small populations, Briggs says. Hence, Neanderthals numbers probably stayed low for a long time.

Chris Stringer, a palaeontologist at the Natural History Museum in London, agrees that Neanderthal populations were probably small. “They must have been on the edge of extinction by this time to have so few people scattered in Europe,” he says.

However during warm spells, their numbers and range probably swelled, only to contract in leaner times, Stringer says. “I think the numbers would have fluctuated. They would have had good times and bad times, and this data reflect that in the last 100,000 years they were having bad times.”

It’s tempting to think that the arrival of modern humans to Europe about 45,000 years ago pushed Neanderthal numbers even lower by competing for increasingly scarce resources. But the invading Homo sapiens would have been relatively rare too, Stringer says. “You’ve got to consider the possibility that they might not have met each other that often.”

Journal reference: Science (DOI: 10.1126/science.1174462)