In a previous post, I said that one of my interests was paleontology. In particular, one of the things I keep an eye on is fossil finds relating to early humans and human ancestors. Over the past 25 years, there have been a number of finds, helping fill in the “family tree,” answering some questions, and posing new ones. In addition to fossils, new technologies are being used. Back in the late 80′s, the Human Genome Project was proposed, and finally started. It was expected to take at least 15 years. Jumps in technology sped that process up, and it only took 10. In the time since, the technology sped up even more, and now genomic sequencing is “normal” – so much so that one journalist calls the reaction to a new genome being published “YAG – Yet Another Genome.”
Scientists have been sequencing genomes from people around the world. Some of this is to see “what’s normal” and some to see “why is this different?” There’s a lot of information and some of it no one knows what it means – yet. Another thing that happened is that scientists decided to see if they could extract DNA from old bones, and fossils. As it turned out, they could – sometimes. Some of the fossils they were able to do it on was one of our closest relatives: Neanderthals. Most of the samples came from European fossils, but one was from Russia, near a place called “Denisova.” That one was only a tooth and a few finger bones, but seemed to be the farthest east of anything found.
Neanderthals have been one of the great questions in human evolution. The fossils said they were different from us. They were stockier, had less chin, and more pronounced brow ridges. The general opinion was that they were a branch of humans, who had split off from the line that lead to modern humans. The big question was how different, and what happened to them? We know that around the time “modern humans” appeared, they disappeared. There were many theories as to what happened to them, ranging from “they were dying out anyways,” genocide, or just out-competed. Being able to get a complete genome from the fossils meant that at least some of those questions could be answered. We’d know how they varied genetically from us. Which is when things got … interesting.
When the Neanderthal genome was compared to modern people’s, something jumped out. A number of their genes were found in modern humans. More importantly, only in people who came from areas outside of Africa. We are carrying a few percent of Neanderthal in our genes. What does that mean? One of the big questions that fossils had never been able to answer was “was there interbreeding?” In other words, did a Neanderthal and an early modern human “hook up?” The fossil evidence said no, or was at best … shaky. The genetics say yes.
But that wasn’t the only surprise. The fossils from Denisova? That turned out to be something new. They were related to us and to Neanderthals – but weren’t the same. They were a whole new branch, now known as the Denisovans. Even more startling, when their genes were compared to modern humans, it turned out that people from southeast Asia and Australia had a few percent of their genes. So as people migrated out, they ran into these people, and interbred as well.
We now have some answers, but the answers pose a lot more questions. We don’t know much about the Denisovans, beyond their genes. We don’t know what benefits the Neanderthal genes gave us, or even answers about the “why?” It’s also shown that the nice neat line that was thought to be human evolution is more convoluted than thought. What were “branches” have grown back into the main trunk. It’s a little more complex. But that’s science. The answers pose new questions.
However, one question has been answered: Did the Neanderthals die out? The answer is no. They became a part of us. Their descendants are running around the world, and one of them is writing this blog. Personally? I think it’s rather neat that I have some old patched genes!