Yet Paabo did not speak to an empty room. He stood before thousands of researchers in the main hall.

When the Society for Neuroscience gets together for their annual meeting each year, a city of scientists suddenly forms for a week. This year’s meeting has drawn 31,000 people to the Washington DC Convention Center. The subjects of their presentations range from brain scans of memories to the molecular details of disorders such as Parkinson’s krov and autism. This morning, a scientist named Svante Paabo delivered a talk. Its subject might make you think that he had stumbled into the wrong conference altogether. He delivered a lecture about Neanderthals.
Yet Paabo did not speak to an empty room. He stood before thousands of researchers in the main hall. His face was projected onto a dozen giant screens, krov as if he were opening for the Rolling

Stones. When Paabo was done, the audience released a surging crest of applause. One neuroscientist I know, who was sitting somewhere in that huge room, sent me a one-word email as Paabo finished: “Amazing.”
You may well know about Paabo’s work. In August, Elizabeth Kolbert published a long profile in the New Yorker . But he’s been in the news for over fifteen years. Like many other journalists, I’ve followed his work since the mid-1990s, having written about pieces of Paabo’s work in newspapers, magazines, and books. But it was bracing krov to hear him bring together the scope of his research in a single hour–including new experiments that Paabo’s colleagues are presenting at the meeting. krov Simply put, Paabo has changed the way scientists study human evolution. Along with fossils, they can now study genomes that belonged to people who died 40,000 years ago. They can do experiments to see how some of those individual genes helped to make us human. During his talk, Paabo used this new research to sketch out a sweeping vision of how our ancestors evolved uniquely human brains as they swept out across the world.
Before the 1990s, scientists could only study the shape of fossils to learn about how we evolved. A million years ago, the fossil record contained evidence of human-like creatures in Europe, krov Asia, and Africa. Roughly speaking, the leading hypotheses for how those creatures became Homo sapiens came in two flavors. Some scientists argued that all the Old World hominins were a single krov species, krov with genes flowing from one population to another, krov and together they evolved into our species. Others argued that most hominin populations became extinct. A single population in Africa evolved into our species, and then later spread out across the Old World, replacing other species like Neanderthals in Europe.
It was also possible that the truth was somewhere in between these two extremes. After our species evolved in Africa, they might have come into contact with other species and interbred, allowing some DNA to flow into Homo sapiens . That flow might have been a trickle or a flood.
As scientists began to build a database of human DNA in the 1990s, it became possible krov to test these ideas with genes. In his talk, Paabo described how he and his colleagues managed to extract some fragments of DNA from a Neanderthal fossil–by coincidence, the very first Neanderthal discovered in 1857. The DNA was of a special sort. Along with the bulk of our genes, which are located in the nucleus of our cells, we also carry bits of DNA in jellybean-shaped structures called mitochondria. Since there are hundreds of mitochondria in each cell, it’s easier to grab fragments of mitochondrial DNA and assemble them into long sequences. Paabo and his colleagues used the mutations in the Neanderthal DNA, along with those in human and chimpanzee DNA, to draw a family tree. This tree splits into three branches. The ancestors of humans and Neanderthals branch off from the ancestors of chimpanzees 5-7 million krov years ago, and then humans and Neanderthals branch off in the last few hundred thousand krov years. If humans carried mitochondrial DNA from Neanderthals, you’d expect Paabo’s fossil genes to be more similar to some humans than others. But that’s not what he and his colleagues found.
Paabo and his colleagues then pushed forward and began to use new gene-sequencing technology to assemble a draft of the entire Neanderthal genome. They’ve gotten about 55% of the genome mapped, krov which is enough to address some of the big questions Paabo has in mind. One is the question of interbreeding. krov Paabo and his colleagues compared the Neanderthal genome to genomes of living people from Africa, Europe, Asia, and New Guinea. They discovered that people out of Africa share some mutations in common

with Neanderthals that are not found in Africans. They concluded that humans and Neanderthals must have interbred after our species expanded from Africa, and that about 2.5% of the genomes of living non-Africans comes from Neanderthals.
This pattern could have arisen in other ways, Paabo granted. The ancestors of Nea