A new study finds that animals with a pair of matching sex chromosomes have a greater life expectancy. Share on Pinterest Across several species of animals, males exhibit mating behavior that may cost them their longevity, new research suggests. In humans and other mammals, females are homogametic, meaning they have two X chromosomes. The males are heterogametic, which means they have two different sex chromosomes — an X chromosome and one “smaller” Y chromosome. A new report from researchers at the University of New South Wales in Sydney, Australia, suggests that having a pair of the same sex chromosomes may be part of the reason females live longer. The authors find that across the animal kingdom, those with two identical sex chromosomes live an average of 17.6% longer than those with two different kinds of sex chromosomes. The paper appears in The Royal Society journal Biology Letters.

Diverse and yet the same Mammals are not the only animals in which a pair of matching chromosomes have associations with a particular sex. Also, not all females are homogametic. Male birds and some reptiles, for example, have ZZ chromosomes, while females are heterogametic, having a ZW chromosome combination. Some animals do not have a second sex chromosome at all, including most male arachnids. Using existing data from scientific books, papers, and online databases, the researchers studied the longevity records of both sexes in 229 animal species, including 99 families, 38 orders, and eight classes. Says lead author ecologist Zoe Xirocostas, “I thought it was really cool how, across insects and fish, we’re all showing the same sort of response.” The researchers found that those species in which the females have a pair of matching sex chromosomes see a more significant boost in longevity than homogametic males do. In species such as mammals, insects, fish, and some reptiles — where females are the homogametic sex — females live 20.9% longer. In species where the males are homogametic, such as birds and butterflies, the increase in lifespan is just 7.1%.