Science believes that genes play a major role in our health. We believe that, if our parents lived a long life, so will we, and if they had a major illness, we’re bound to get it too. Much research is devoted to finding the genes responsible for all kinds of diseases and conditions as well as ways to manipulate the genes to prevent the disease from being passed on.

Now some doubt has been cast on this theory. While many things are inherited, it seems that there are very few diseases that we’re likely to get just because our parents got them. Cancers, for instance, which are thought to be strongly inherited, turn out not to be. In a study conducted in 2000 that looked at nearly 45,000 pairs of twins, researchers found only three types of cancer that are likely to occur in both twins. And even for those, the probability was very low: if one twin had the disease, the chances of the other one getting the same cancer was only 15%.

This, and much more, is described in a wonderful New York Times article, Live Long? Die Young? Answer Isn’t Just in Genes.