Neanderthals were close relatives of present-day humans, but despite their control of fire and ability to make and use tools, they died out while people have spread. The genomes of Neanderthals have shown, writes Svante Pääbo in the New York Times, that they were genetically very similar to people. By comparing human and Neanderthal genomes, Pääbo and his colleagues have found that there are some 31,389 genetic mutations that modern people have.
"Among these mutations may lurk some subtle yet consequential differences between them and us that further research may eventually explain," he adds.
However, he notes, there are different ways to go about that work.
Some researchers, Pääbo says, have suggested engineering human stem cells to produce a Neanderthal embryo and re-create a Neanderthal individual. While Pääbo says this may not even be technically possible as the Neanderthal genome is incomplete, he also says that it should not be ethically permissible.
"Neanderthals were sentient human beings, after all," he writes in the Times. "In a civilized society, we would never create a human being in order to satisfy scientific curiosity."
Instead, Pääbo argues that Neanderthal stem cells could be created and developed not into individuals but into cells and tissues that could be studied in the lab. For instance, he writes that Neanderthal nerve cell function genes could be introduced into human stem cells that are then reprogrammed to become neurons that could then be studied.
"Perhaps much more of what we share and do not share with the Neanderthals can be revealed in this way," he says.