THE BETTER HALF

A male physician and scientist argues that “women are simply stronger than men at every stage of life.”

Moalem (The DNA Restart: Unlock Your Personal Genetic Code To Eat for Your Genes, Lose Weight, and Reverse Aging, 2016, etc.) attributes female superiority largely to the two X chromosomes that determine female sex in humans, as opposed to the single X and much smaller Y chromosome that determines maleness. The two X’s vary—one inherited from the father and one from the mother—so they enrich the genetic library women can draw upon. The conventional wisdom is that one of a woman’s X’s is silenced in each of her cells and that this happens randomly, so that, say in the kidney, one cell may have the mother’s X silenced and be next to a cell that has the father’s X silenced. This means that even if there is a bad gene on one of the X’s, the other X will be present in sufficient numbers to compensate. Now, however, that conventional wisdom may need amending. There is evidence that some genes on the silenced X chromosome are functional, adding extra genetic power to females. Further, as Moalem accessibly explains, female cells can cooperate. For example, one female cell can generate an enzyme sorely needed by another female cell whose X has a mutation in the necessary gene. All this genetic endowment also leads to a more potent immune system, which is one of the reasons women generally outlive men; they are better survivors of infection and disease across the life span. There is a downside, however: Having a finely tuned immune system also leads to higher prevalence of autoimmune diseases in women. Ischemic stroke and Alzheimer’s are also more common in women, for unknown reasons.

Moalem’s sharp text serves as a challenge to explore the vast unknown territory of chromosomal differences in men and women.