A future without men?

2 minute read

H. Allen Orr reviews Brian Sykes' book, Adam's Curse: A Future Without Men in the May 12, 2005 New York Review of Books. This is a great review (with short comparisons to Steve Jones' Y: The Descent of Men and David Bainbridge's The X in Sex: How the X Chromosome Controls Our Lives

From the review:

Sykes's case for the extinction of men hinges on an unusual problem plaguing many genes on the Y chromosome -- they tend to pick up debilitating mutations and to ultimately degenerate into genetic junk. A couple of hundred million years ago or so, the X and Y were a pair of perfectly ordinary chromosomes that each carried a full complement of the same thousand genes. Since then, however, the Y has been slowly degenerating. As a result, while the human X still carries its thousand genes, the Y carries only about a hundred. Sykes believes that the genes that remain on the Y -- including SRY as well as others required for the fertility of men -- will also degenerate. The disastrous consequence, he says, will be the disappearance of fertile males. (Sykes sometimes says that males will become sterile, while at other times he suggests they'll disappear. Genetically, at least, the difference doesn't make a difference: if all males are sterile, they may as well not be there.)
I'm afraid that this is all just silly. ... The critical point is that most of the male fertility genes now residing on the human Y exist only on that chromosome and there's no way that selection will allow their loss.
Sykes's calculation suggests otherwise because it's wrong. He seems to assume that Y chromosomes carrying mutations that partially sterilize men will get passed on to future generations as often as normal, unmutated chromosomes. But they won't -- that's what it means to be partially sterile. This misstep leads Sykes astray. There are simply no sound evolutionary grounds to support his sensational claims of the extinction of men.

In this book, Sykes constructs and defends a fairly extreme model of biological determinism for the Y chromosome, drawing historical and prehistoric human events into the fold of this model. So war, empire, and Genghis Khan himself is drawn into the story. It is good to see Orr skewering this model and its lack of fundamental population genetic logic.

Personally, I can't see the appeal of reading a book entirely about a single chromosome. Not that most chromosomes don't have interesting stories -- hey, why not chromosome 11? -- or that you can't associate human stories with a chromosome. I regularly assign Matt Ridley's Genome in my intro-level course as a quick overview to how genetics relates to human lives, and that book is essentially a series of 24 essays riffing off each of the human chromosomes (X and Y separate). But it seems to me that chromosomes are a pretty poor way to organize human experience.