What can genes tell us about who we are? Millions of people around the world have begun using consumer ancestry services like 23andMe in an attempt to peer into their personal origins and understand where they came from.

Meanwhile, though, in a handful of elite genetics labs around the world, scientists have begun analyzing ancient DNA — which can now be extracted from skeletal remains that are thousands or even tens of thousands of years old — to ask, and try to answer, even more fundamental questions about the human past.

In only the past few years, as a new report in The New York Times Magazine describes, this burgeoning science of “paleogenomics” has begun to offer surprising revisions to the story of humanity. But at the same time, this research has generated significant controversy, including among some of the archaeologists, anthropologists and other academics who have collaborated with geneticists on this work.

Here are some key takeaways.

The study of ancient DNA has upended many of our assumptions about prehistoric times.

For decades, it was commonly believed that ancient communities tended to stay in one place — and thus didn’t mix very much with their neighbors. When a lab in Leipzig, Germany, sequenced the majority of a Neanderthal genome, in 2010, the scientists surprised just about everybody with the finding that humans and Neanderthals had actually interbred; we now know that most people, with the general exception of sub-Saharan Africans, can trace part of their genetic inheritance to our extinct cousins.