For many years, scientists have wondered why Neanderthals disappeared after surviving for hundreds of thousands of years.
A new study suggests that, at least in parts of Western Europe, Neanderthals were still healthy and thriving shortly before they vanished.
The research, published in Nature, examined the DNA of Neanderthals who lived in what is now Belgium and France between about 49,000 and 40,000 years ago.
Surprisingly, the scientists found no evidence that this population was in decline, even though Neanderthals became extinct only about 2,000 years later.
Neanderthals lived across a huge area that stretched from Western Europe to Central Asia. They survived major climate changes and lived alongside modern humans for a period of time before disappearing around 40,000 years ago.
Scientists still debate exactly why they went extinct. Possible reasons include climate change, competition with modern humans for food and resources, and interbreeding with our own species.
To better understand what happened, researchers analyzed DNA taken from the bones of 27 Neanderthals found in the Meuse Basin, a region that covers parts of Belgium and France.
One of the biggest surprises was that the researchers found no signs of close inbreeding. In some earlier Neanderthal populations, close relatives often had children together because groups were small and isolated.
Over time, this reduced genetic diversity and increased the risk of harmful inherited traits.
In this newly studied population, however, none of the individuals were closely related, even at the level of first cousins. This suggests that the Neanderthals were part of larger, well-connected communities where people could find unrelated partners from nearby groups.
The researchers also studied mitochondrial DNA, which is passed from mothers to their children. Most of the Neanderthals shared a common maternal family line that was widespread across Southern and Southwestern Europe.
However, one individual belonged to a different maternal line, showing that multiple family groups lived in the region at the same time.
The team also examined Y chromosomes, which are passed from fathers to sons. The three male individuals studied each came from different paternal family lines, adding more evidence that the population had healthy genetic diversity.
Scientists also searched for long stretches of identical DNA, which are a sign that parents were closely related. They found very little evidence of this. That means these Neanderthals were not suffering from what scientists call inbreeding depression, a condition that can reduce fertility, increase inherited diseases, and make it harder for populations to survive environmental changes.
The findings also showed that Neanderthals in Western Europe were more closely related to one another than to Neanderthal groups living elsewhere, but there was still enough movement between communities to keep their gene pool healthy.
Interestingly, all the remains found at one site called Goyet belonged to unrelated females, young males, and one newborn baby, offering a small glimpse into the makeup of one Neanderthal community.
The study raises an important question. If these Neanderthals were healthy and genetically diverse, why did they disappear so quickly?
The researchers believe Western Europe was likely a good place for Neanderthals to live at the time. However, conditions may have changed rapidly. A shift in climate, increasing competition with modern humans, or a combination of both may have pushed even these healthy populations beyond the point where they could survive.
The new findings suggest that Neanderthal extinction was probably not caused by poor genetic health alone. Instead, it may have resulted from powerful environmental and social changes that unfolded over a relatively short period of time.
Source: KSR.
