Neanderthals and Humans Interbred for Nearly 7,000 Years, Research Finds

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New research indicates that humans and Neanderthals interbred 47,000 years ago over a period spanning almost 7,000 years.

This extended period of interbreeding has left lasting genetic traces in modern humans.

The study analyzed DNA from both prehistoric and contemporary human populations, providing significant insights into our ancient interactions with Neanderthals.

Understanding Neanderthals and Modern Humans

Neanderthals, our closest extinct relatives, diverged from the common ancestors of modern humans about 500,000 years ago.

These ancient relatives shared many similarities with Homo sapiens but were a distinct group.

Around 10 years ago, scientists discovered that Neanderthals interbred with the ancestors of modern humans who migrated out of Africa.

Today, approximately 1% to 2% of the DNA in modern human populations outside of Africa is of Neanderthal origin, a testament to these ancient encounters.

Research Details

To pinpoint the timing and duration of this interbreeding, researchers examined over 300 human genomes covering the last 45,000 years.

This extensive analysis included DNA from 59 ancient individuals and 275 contemporary humans from diverse backgrounds.

The scientists posted their findings on the BioRxiv preprint database.

Their results suggest a major period of interbreeding starting about 47,000 years ago, lasting approximately 6,800 years.

Where and How It Happened

Modern humans began migrating out of Africa at least 194,000 years ago.

As they moved into new territories, they likely encountered Neanderthals in western Asia, a region where Africa connects with Eurasia.

This area would have been a prime location for these two groups to meet and interbreed.

Humans carrying Neanderthal genes then spread across various parts of the globe, taking these genetic markers with them.

Impact on Modern Humans

The interbreeding with Neanderthals has had a lasting impact on modern humans.

Neanderthal DNA has influenced various traits, such as skin color, metabolism, and immune system function.

These traits likely provided adaptive advantages as modern humans encountered different environmental pressures outside Africa. Initially, over 5% of the modern human genome was composed of Neanderthal DNA.

This means that roughly one in every 20 ancestors in the early human population was a Neanderthal.

Other Interbreeding Events

While the study focused on a major interbreeding period 47,000 years ago, there may have been other instances of interbreeding that did not leave significant genetic marks.

For example, a human jawbone found in Romania, dating back 37,000 to 42,000 years, contains Neanderthal DNA not found in other modern human genomes.

This suggests that there were additional interbreeding events that did not contribute to the genetic diversity of contemporary humans.

Implications and Questions

The findings suggest that human dispersal out of Africa occurred later than previously thought, confined to less than 47,000 years ago

This contrasts with archaeological evidence suggesting human presence in northern Australia about 65,000 years ago.

This discrepancy raises several possibilities: the archaeological evidence might be incorrect, the early populations could have gone extinct or been replaced by later waves of migration, or the early inhabitants might not have been Homo sapiens.

Additionally, there is little evidence that modern human DNA entered Neanderthal genomes, hinting at potential differences in behavior or reproductive challenges between the two groups.

It is possible that hybrids with modern human DNA were less successful, less healthy, or less fertile, preventing the reverse gene flow from being significant.

Conclusion

This research offers a deeper understanding of a significant period in human history, highlighting the complex interactions between our ancestors and Neanderthals.

The study of ancient DNA continues to unravel the intricate story of our origins, revealing how interbreeding with Neanderthals has shaped the genetic makeup of modern humans.


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