Archaeologists and paleontologists are up against the same problem; bones and other fossils only get you so far.
There are cases where fossil evidence can give you some hints about behavior -- patterns of tracks, for example, or the rare case where the positions of the fossils themselves give you a picture of what was going on, like the recent discovery of an opossum-sized mammal, Repenomamus, attacking a much larger dinosaur, Psittacosaurus. The pair of fossil skeletons were preserved, locked in a battle to the death -- the death of both, as it turned out, because they were both engulfed mid-fight in a mudslide.
But such lucky finds are rare, and inferences of behavior from fossils are usually sketchy at best. This is why the study of a group of Neolithic human skeletons found near Gurgy-les-Noisats, France, 150 kilometers southeast of Paris, was so extraordinary.
The level of DNA analysis now possible allowed the analysis of the genomes of 94 of the 128 individuals buried at the site, to the level that the researchers not only were able to construct a seven-generation family tree for them, but make a guess as to what each individual looked like.
The analysis found that the bodies were buried in family groups -- the more closely two people were related, the closer together they were buried -- and that women who were not descendants of the original couple were mostly completely unrelated, suggesting they'd come into the family from another community. Just about all the males at the burial site, on the other hand, were related, leading the researchers to conclude that men in this community tended to stay put, and at least some women did not.
Another curious thing was that the study detected no half-sibling relationships. All of the sibling groups were from the same mother and father. In this family group, at least, monogamous relationships were the norm.
Of course, there's a lot we still don't know; while this is a stunning accomplishment, it still leaves a great many questions unanswered. For example, were the "outsider" women brought in because of a custom of outbreeding, or by conquest/capture? What were the religious practices and beliefs that led these people to bury family members near each other? Was the monogamy shown in this family universal in this culture, or was this grouping an exception for some reason?
It's an intriguing piece of research. "This type of work really breathes new life into our understanding of ancient peoples," said Kendra Sirak, an ancient-DNA specialist at Harvard Medical School in Boston, Massachusetts, who was not involved in the study. "I'm especially curious about the man at the root of the family tree. I would love to know what made this person so important."
And given that a significant percentage of my ancestry comes from central and western France, I have to wonder if anyone in this family tree is a direct ancestor of mine. There's no way to find out, of course, but the thought did cross my mind. It's kind of eerie to think when I look at those facial reconstructions, one of those faces looking back at me might be my great-great (etc.) grandparent.