Give me two!
The most probable explanation of why women live longer than men has been found
Sergey Kolenov, Hi-tech+
Australian scientists have found that the life expectancy of males and females in various animal species depends on the composition of sex chromosomes. Those who carry two identical sex chromosomes live longer than those who have different ones. This explains why the life expectancy of women (with a set of XX chromosomes) is higher than that of men (XY).
It is widely known that women live longer than men. This feature is also characteristic of many other mammalian species. But in birds, the opposite is true: the average life expectancy of males is higher than that of females.
One hypothesis explains these differences by the composition of sex chromosomes. The genome of males of most mammals contains unpaired sex chromosomes (XY), and in females – paired (XX). In birds, sex is determined differently – females carry two different sex chromosomes (ZW), and males – the same (ZZ).
It is easy to assume that the second copy of the sex chromosome serves as a kind of "insurance" in case the first mutates. The chromosome that remains unchanged will continue to work normally, so the effect on the cells will be minimal. However, if the copies are different, any mutation in the sex chromosome will immediately manifest itself. Perhaps this is exactly what happens in the cells of male mammals and female birds, as a result of which their life expectancy is shortened.
To test this idea, researchers from The University of New South Wales collected data on the sex chromosomes and life expectancy of 229 animal species, from insects to fish and mammals. Hermaphrodites and species whose sex is determined by the temperature of the environment during embryonic development were not included in the analysis.
Article by Xirocostas et al. The sex with the reduced sex chromosome dies earlier: a comparison across the tree of life is published in the journal Biology Letters, the press release Why men (and other male animals) die younger: it's all in the Y chromosome can be read on the website of the University – VM.
As the results of the study demonstrated, the presence of paired sex chromosomes increases life expectancy by an average of 17.6% compared to those who have different chromosomes or only one sex chromosome is present in the genome.
However, the gain from the "spare" chromosome was different for different sexes. For males, the presence of two identical sex chromosomes on average increased life by 7.1%, and for females – by 20.3%. Perhaps this is due to the fact that males are often at greater risk, for example, when fighting for a female or searching for new territories. Another possible explanation is the protective effect on the chromosomes of the female sex hormone estrogen.
Of course, the composition of sex chromosomes cannot be considered the only factor determining the life expectancy of males and females. It is also influenced by other features of each species, from the way food is obtained to social interaction. Thus, if this is a pattern, then with numerous exceptions, as it often happens in nature.
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