Did infertility kill off the Neanderthals? Mysterious disappearance could be explained by just a 2.7 per cent decline in female fertility
- There is currently no accepted theory for why Neanderthals died out
- Focus mainly on catastrophic events such as disease, warfare or climate change
- New theory suggests it may actually be a result of decreasing female fertility
- Found a drop of 2.7 per cent would see the species eradicated in 10,000 years
- But a five and eight per cent decline accelerated this to 6,000 and 4,000 years respectively
Neanderthals may have gone extinct because the women of the ancient species slowly became infertile, researchers suggest.
Scientists have yet to agree on a single reason explaining why they disappeared.
Current theories focus on catastrophic events such as disease, warfare or climate change wiping them out, but there is little evidence supporting this.
A researcher from France looked into the possibility it was instead due to decreasing fertility and investigated how much of an impact it would have on the long-term survival of the entire species.
Mathematical models revealed a decrease in fertility of just 2.7 per cent would see the species eradicated in 10,000 years.
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Scientists have yet to agree on a single reason explaining why they disappeared. Current theories focus on catastrophic events such as disease, warfare or climate change wiping them out, but there is little evidence supporting this (file photo)
The research used computer models to predict how soon extinction came and was conducted by a team led by Anna Degioanni from Aix-Marseille University.
They looked at what would need to have changed in Neanderthal groups to see the population fall below 5,000 – which the study considered to be functionally extinct.
It included female fertility, adult mortality and infant survival rates.
They looked at what subtle changes would be needed to make them extinct in 4,000 years, 6,000 years and 10,000 years.
These time frames are considered by many scientists to be the most likely periods of time it took for Neanderthals to die out.
Researchers primarily focused on female fertility and found a 2.7 per cent drop would be enough to make the species extinct in ten millennia.
But a five and eight per cent decline sped their demise up to just 6,000 and 4,000 years, respectively.
The researchers write in the paper: ‘We show that, in the long run, a slight change in the fertility rate of younger females could have had a dramatic impact on the growth rate of Neanderthal metapopulation and thus on its long-term survival, in agreement with the observed extinction of Neanderthals within a 10,000, 6,000 or 4,000 years period’
| Years to extinction | Female fertility | Infant mortality |
|---|---|---|
| 10,000 | -2.7% | -0.4% |
| 6,000 | -5% | -1% |
| 4,000 | -8% | N/A |
Mathematical models revealed a decrease in fertility of just 2.7 per cent would see Neanderthals eradicated in 10,000 years. But a five and eight per cent decline accelerated this to 6,000 and 4,000 years respectively
A reason behind the decline is not stated by the researchers, but they tentatively suggest it would likely have originated from food scarcity.
The authors add: ‘Because the amount of stored body fat influences fertility in women a decline in resources (caused by climate degredation or competition with sapiens) may affect fertility mostly for young women giving birth for the first time.’
The study was published in the journal PLOS ONE and also discovered infant survival rate would have to be decreased by just 0.4 per cent to send them extinct in 10,000 years.
A marginal increase to one per cent sees this jump enormously to just 6,000 years, showing how important survival of offspring was to Neanderthals.
Like humans, they reproduced slowly and invested heavily in their children. other mammals have large litters to compensate for low survival rates but primates, and hominins especially, invest a large amount of resources in a few young.
A further finding in the study was that if adult survival was slashed by ten per cent it would have a catastrophic impact on the species as a whole, causing almost instant extinction.
Researchers suggest either disease from Homo sapiens or warfare a likely source of this sort of rapid decline.
WHO WERE THE NEANDERTHALS?
The Neanderthals were a close human ancestor that mysteriously died out around 50,000 years ago.
The species lived in Africa with early humans for hundreds of millennia before moving across to Europe around 500,000 years ago.
They were later joined by humans taking the same journey some time in the past 100,000 years.
The Neanderthals were a cousin species of humans but not a direct ancestor – the two species split from a common ancestor – that perished around 50,000 years ago. Pictured is a Neanderthal museum exhibit
These were the original ‘cavemen’, historically thought to be dim-witted and brutish compared to modern humans.
In recent years though, and especially over the last decade, it has become increasingly apparent we’ve been selling Neanderthals short.
A growing body of evidence points to a more sophisticated and multi-talented kind of ‘caveman’ than anyone thought possible.
It now seems likely that Neanderthals buried their dead with the concept of an afterlife in mind.
Additionally, their diets and behaviour were surprisingly flexible.
They used body art such as pigments and beads, and they were the very first artists, with Neanderthal cave art (and symbolism) in Spain apparently predating the earliest modern human art by some 20,000 years.
