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If you ask seniors about their secret for a long life, they usually answer: healthy eating, a little exercise, little alcohol and drinking a lot of water.
One thing they don't mention: chromosomes.
But it is precisely these that probably make the difference why women generally have a longer life expectancy in mammals than their male counterparts.
Specifically: The duplicate X chromosome should be responsible for this.
At least that is the result of a study by researchers at the University of New South Wales in Sydney.
But let's start from the beginning: In mammals, the males have one X and one Y chromosome, the females have two X chromosomes.
Humans have a total of 46 chromosomes including the two sex chromosomes
Source: Getty Images / Science Photo Library RF / KATERYNA KON / SCIENCE PHOTO LIBRARY
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In birds, for example, it is exactly the other way around: in them the males have two Z chromosomes, while the females have one Z and one W chromosome.
So with these species, the men have an advantage.
The so-called homogamy, the double presence of a chromosome, is said to be decisive for longer life expectancy.
Because this means that important genetic information is available twice.
If one of these has mutated defective, the second, healthy version can compensate for the damage.
This hypothesis has been circulating in the research world for years.
The Australian scientists have now checked.
To do this, they examined the life expectancy of a total of 229 animal species.
“We not only looked at data from primates, other mammals and birds, but also from reptiles, fish, amphibians, arachnids, cockroaches, grasshoppers, beetles, butterflies and moths,” says study author and biologist Zoe Xirocostas in one Press release continues.
In butterflies, as in birds, the males are homogametic and carry two Z chromosomes
Source: Getty Images / sandra standbridge
In fact, the analyzes showed that across the animal kingdom, sex with two identical sex chromosomes lived longer - by an average of 17.6 percent.
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Small informal insert: In Germany, according to the Federal Institute for Population Research, the average life expectancy in 2016 was 83.3 years for women and 78.5 years for men.
What surprised the researchers: Homogametic males (such as birds) live an average of 7.1 percent longer than their wives, homogametic females (such as we humans) even live 20.9 percent longer than their men.
Heterogametic men with two different sex chromosomes therefore have a double disadvantage: They not only have a shorter life expectancy than their wives.
They also lose out in comparison with heterogametic females and die earlier than them.
Source: Getty Images / Cheng Jung Kuo
Why are the lords of creation so disadvantaged?
On the one hand, according to the scientists, the Y chromosome of the heterogametic male could be even more stunted compared to his homogametic counterparts.
On the other hand, the female sex hormone estrogen could also have a positive effect on women.
We already know that it promotes the enzyme telomerase, which surrounds the chromosomes and protects the DNA underneath.
Or third: males are subject to more intense sexual competition than females.
They have to take comparatively greater risks and fight more dangerous battles in order to reproduce.
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In the future, further investigations are to examine the explanatory approaches in more detail.
For the moment, however, the researchers are satisfied that they have been able to confirm the hypothesis that homogamy has a positive effect on men.
This article was first published in March 2020.