Page pointed out that, while the Y chromosome may not share genetic material with the X chromosome, it can swap genes with other chromosomes as well as keep multiple copies of functional genes to increase their number on the Y chromosome. Makova and Wilson said that the increased rate of mutation on the Y chromosome could give rise to new genes that may prove beneficial and, therefore, remain on the chromosome.
Genetic change, whether by mutation, environmental stressors or by swapping bits of chromosomes, is the natural course of evolution, and evolution is weighted towards survival. Perhaps most importantly, Y chromosomes with defective male-specific genes, especially those involved in sperm production, are unlikely to reproduce and pass on those genes to their sons, which knocks highly defective chromosomes out of the gene pool. Genetic changes that do not favor reproduction are likely to get weeded out of the system.
"The most fundamental [principle] to all evolution is reproduction," said Dr. Ronald Crystal, chairman of the Department of Genetic Medicine at Weil Cornell Medical College. "No one knows why the Y chromosome has more pressures to evolve. It may be that the genes are irrelevant. ... But evolution figures out a way to maintain reproduction."
Even if the Y chromosome becomes obsolete, reproduction will continue, in some form. Makova and Wilson said that new sex chromosomes may rise from non-sex chromosomes or that essential genes might move to other chromosomes, which has happened in some species of deer.
"Presumably, we will have moved genes around," said Dr. Harry Ostrer, director of the Human Genetics program at the New York University School of Medicine. "But the reproductive structures will be well conserved."
In other words, men will not fade away, even if their Y chromosomes do.