Bryan Sykes, a professor of human genetics at Oxford University, says that because the Y chromosome doesn't mix with other genes, and is therefore unable to heal itself from genetic wounds, men will eventually become extinct.
Seven percent of men are infertile or sub-fertile and in roughly a quarter of cases the problem is traceable to new Y chromosome mutations, not present in their fathers, which disable one or other of the few remaining genes. This is an astonishingly high figure, and there is no reason to think things will improve in the future -- quite the reverse in fact. One by one, Y chromosomes will disappear, eliminated by the relentless onslaught of irreparable mutation, until only one is left. When that chromosome finally succumbs, men will become extinct.Brian Carnell says: "a recent study demonstrated that the Y chromosome does have the ability to repair genetic damage to itself through a rather unique method." Link