The social environment, then, is genetics one degree removed. And vice versa.

When scientists started decoding the human genome, many assumed the nature-nurture debate was over and the hereditarians had essentially won. Soon we’d know the genetic blueprints for everything: obesity, intelligence, susceptibility to chronic diseases, even individual personality traits. Pharmaceutical companies would develop drugs that could target the handful of genes responsible for, say, arthritis or heart disease or schizophrenia. The end of illness would soon be at hand.

It wasn’t that simple. These outcomes are controlled not by a few genes but by thousands of tiny variants across all your chromosomes, far too many to be just zapped away. Scientists did get something out of the inquiry, however. Starting around 2009, they found a way to summarize all these small genetic influences into a single metric that they called the polygenic index. Think of it as a FICO credit score for your biology. Or rather scores, plural, since there is a different one for each and every outcome we can measure.

Scientists don’t all agree about what to make of this new data or whether it can apply equally to all populations, but today roughly 6,000 studies have identified polygenic indexes, or PGIs, for more than 3,500 traits, from sleep habits to right- or left-handedness and extroversion. These indexes are not crystal balls, to say the least. They can’t tell you anything with certainty, and in some arenas they can’t really tell you anything at all, at least not yet. But they can offer some very tantalizing clues. Take the PGI for educational attainment — that is, how far we go in school. Research I participated in found that among adults whose scores were in the lowest tenth on that PGI, only 7 percent had finished college. Among those whose scores were in the top tenth, that number was 71 percent. That’s a significant gap.

At the same time, it’s far from destiny. Clearly, genes alone are not enough to explain the course of people’s lives, even if someday we get much better data than this nascent field can currently provide.

So what, then, should we do with those PGI scores, which — as the field of sociogenomics reveals — tell us so much and yet so little?