I recently watched a lecture called Homo sapiens Meets Neanderthals: The End of a World by Professor Jean-Jacques Hublin. The focus of the talk was on how Homo sapiens entered Eurasia and interacted with Neanderthals. It was intriguing to see how complicated the process was.
One of the most interesting facts was how long the two groups overlapped. Researchers used to think modern humans entered Europe around 40,000 years ago, but discoveries at Bacho Kiro in Bulgaria and Ranis in Germany revealed that Homo sapiens were present in Europe around 45,000-47,000 years ago. Since Neanderthals were present in parts of Europe until around 40,000 years ago, the two groups may have lived near each other for thousands of years.
The genetic evidence was also fascinating, as most people with ancestry outside Africa carry about 2% Neanderthal DNA. By studying the size of Neanderthal DNA segments, scientists could estimate when interbreeding occurred. Dr. Hublin explained that the main period of mixing likely happened around 45,000 to 49,000 years ago. What was especially interesting was that the size of these gene fragments can give scientists information about how long ago the two populations mixed. As time passes and DNA is passed down through generations, recombination causes the inherited Neanderthal sequences to become increasingly fragmented. Larger Neanderthal DNA sequences therefore suggest more recent mixing between the gene pools, while smaller sequences suggest that the mixing happened further in the past and that the original sequence has been broken into smaller pieces over time. I knew that DNA could reveal that interbreeding occurred, but I did not realize that the size of the fragments could also help scientists estimate when it happened.
My favorite part of the lecture was learning about ZooMS, which stands for Zooarchaeology by mass spectrometry. ZooMS is a technique that identifies tiny bone fragments by analyzing collagen proteins. Most of the bone fragments scientists recover from archaeological excavation sites are from animals, while only a small portion come from humans. This creates a problem because many fragments are too small or damaged to identify just by looking at their shape. ZooMS gives scientists a way to search through large numbers of these fragments and identify the rare human ones.
First, you start by extracting a small sample of collagen from a bone fragment. Then, using enzymes, the collagen is broken down into peptides. A mass spectrometer is used to measure the masses of the different peptides. Different species have characteristic patterns of peptides, almost like a molecular fingerprint. Scientists can compare the pattern from an unknown bone fragment with reference samples to determine which species it came from. This allowed scientists to find human remains that would otherwise be overlooked. Once a fragment is identified as human, scientists can study it further. The fragment can potentially be directly dated, and researchers may also be able to extract DNA from it to learn more about the individual and the population it belonged to. I thought it was interesting that a tiny bone fragment that might initially look unimportant could provide both chronological and genetic information about humans who lived tens of thousands of years ago. I love learning about new techniques, especially those that combine biology and technology.
The lecture changed how I thought about Neanderthal extinction. Their disappearance wasn’t a sudden event, but a long process over 700 years involving migration and interbreeding, with their DNA living on in us. Around 40,000-41,000 years ago, Neanderthals disappeared, replaced by Homo sapiens, but their DNA still lives on, leading to questions about the significance of that 2% most humans carry. What features did that 2% affect that caused it to be passed on so consistently? Where and when did the Neanderthals and Homo sapiens reproduce? Were there other variants of this mix that failed to reproduce? Learning how scientists can connect archaeological remains with genetic evidence made this especially interesting.
