Ancestry was totally wrong about my feelings toward cilantro—they say I'm prone to disliking the herb, but I love it—but they nailed this one.
On the other hand, they are 180% out of phase in calling me a night person. Ideally, I'd sleep from 9:30 to 5:00.
So? About as reliable as a horoscope or a gypsy fortune teller?
Maybe, though overall I've found them more reliable than not; it's the areas of disagreement that stand out.
It's a statistical thing, with all the insights and dead-ends statistical analysis can give you. There's a huge database of DNA out there, albeit currently biased towards those of European ancestry (because the sample is self-selected). If we have given permission (another form of self-selection), companies like Ancestry and 23andMe make their anonymized data available for scientific research. They are careful to make the point that what they provide is not itself scientific research, but gives scientists data from which to form hypotheses and choose a direction and an approach for their research. For example, the data indicate that people with blood type A are more likely to have problems with COVID-19 than people with blood type O. (I may have the details wrong here, but you'll get the idea.) In itself, that proves nothing, but has inspired research into why it might be, in hopes of learning more about the disease and its treatment.
Statistically, most people in Ancestry's database with a bunch of the same genetic markers I have are night people, like to take naps, and hate cilantro. All statistical analysis reveals outliers. For my love of cilantro and the morning hours, I am one; for naps, I am not. Ancestry and 23andMe are careful to point out that our DNA is not a fixed destiny; how our genes are expressed can be affected by how we live.
More fascinating yet, Sharon Moalem's book Inheritance: How Our Genes Change Our Lives—and Our Lives Change Our Genes (thanks, Sarah!) reveals that how we live can even impact how we express our genetic inheritance to our children.
