Human male infertility, the Y chromosome, and dinosaur extinction

Study of the molecular genetics of human male infertility and the Y chromosome has helped to elucidate the evolution of our X and Y chromosomes. Particularly, the study of the Y chromosome in male infertility has also helped to clarify, in a surprising and unexpected way, a likely mechanism for dinosaur extinction, the biggest question all of us have entertained from our earliest childhood days.There have been many claims in the popular press of “discoveries” on how the dinosaurs went extinct. These claims all relate to climate change events that occurred 65 million years ago that no one disputes occurred. But none have explored the biology of how so many animals escaped extinction while the dinosaurs and at least half of all other species did not. For example, why did large dinosaurs, as well as small dinosaurs the same size as chickens go extinct, but birds survived? Possibly the evolution of sex chromosomes holds the answer to this question.Our studies of the Y chromosome and male infertility suggest that the default mechanism for determining the sex of offspring is the temperature of egg incubation, and that genetic sex determination (based on sex chromosomes like X and Y) has evolved many times over and over again in different ways, in different genera, as a more foolproof method than temperature variation of assuring a balanced sex ratio in offspring. The absence of such a genetic sex determining mechanism in dinosaurs may have led to a skewed sex ratio when global temperature dramatically changed 65,000,000 years ago, resulting in a preponderance of males, and consequentially a rapid decline in population.