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Evidence for Gender Longevity Differences to Arise from Mating Strategies

That females live longer than males in numerous species is a topic of some interest to evolutionary theorists and other researchers in the life sciences. There are any number of possible explanations, but that this phenomenon exists in many different species tends to favor evolutionary arguments. Something fundamental to gender as it exists in most higher species is closely tied to aging, and the result is near always females that age more slowly than males. In the research noted here, scientists report on an experiment in fly populations that suggests this longevity difference will arise quite naturally from the differing mating strategies of male and female genders, each under selection pressure to maximize their success in reproduction.

Differences in aging and the length of life between males and females are common in the animal realm. Males often have shorter lifespans than females. Researchers used fruit flies, Drosophila melanogaster, to investigate whether sexual selection lies behind sex differences in aging. They wanted to determine whether the two sexes are affected differently when they are in poorer physical condition, in other words, when they have poorer access to nutrients and energy. In particular, they were interested in the ability of the flies to reproduce, and how this ability changes when the flies age, in a process known as "reproductive aging".

Researchers had manipulated the genetic material of some of the flies, such that they had many small harmful mutations in their genes. These mutations had a negative influence throughout life, meaning that an individual with such mutations converted food to useful energy slightly less efficiently. Thus, even though all of the flies had access to the same food and could eat equal amounts, the manipulated flies were in poorer physical condition.

In order to mate with available females, the aging males were compelled to compete with young males. It turned out, as expected, that males in good physical condition were better at this than those who were in poorer condition, independently of how old they were. The reproductive aging of males, however, decreased at the same rate, independently of whether they were in good or poor physical form. Things were different for females. Early in life, there was no difference between the number of offspring produced by females in good condition, who could use the available resources better, and the number produced by mutated females, who were in poorer condition. The two groups, however, aged at different rates. As the females became older, those who were in good physical form had more offspring than their less fortunate sisters.

"The results show that sexual selection contributes to the differences between the sexes in reproductive aging. This is probably because females in good condition, with good access to nutrients, invest the extra resources into maintaining their bodies, such that they can continue to reproduce to a more advanced age. Males, in contrast, seem to invest a great deal of their resources, independent of their condition, into trying to ensure that they achieve successful mating here and now."

Link: https://liu.se/en/news-item/darfor-aldras-honor-langsammare

Comments

Very interesting study. However, it does not explain why in humans women have menopause at the age when the men can still reproduce just fine. In fact, frim a reproductive point of view, women age faster than men. 35-40 is kinda young for men but women will start having difficulties conceiving

Posted by: Cuberat at October 12th, 2018 8:43 AM

The reason why I will never marry! ;-)

Posted by: Ariel at October 12th, 2018 2:02 PM

Hi, interesting, I think the lacking element of this study is 'extreme longevity'; which flies do not fall in. If we look at extreme longevity we see that indeed, animals that push back sexual reproduction live the longest (puberty entry/adult sexual capability). In mammals, at least, this is the case. That a woman might enter menopause quicker than a man enters andropause may be due to this somatic vs sexual reproduction resource allocation (which this study says that the female flies live longer because they are sexually capable longer (it makes me think of the salmon analogy, the salmon lives 3 years rough, but the infected salmon lives 13 years due to be infected with a host type of bacteria that activates a 'slowing' of aging in it; this infected salmon is sexually capable for all this time while a regular becomes sexually senescent very rapidly). In humans, sexual reproduction is at the junction between resource conservation for somatic maintenance (repair DNA, detoxify and such) vs resources for 'Fitness/sexual capability (this is the mTOR/IGF endrocrine growth domain'.
It was demonstrated that women with highest gravidity (4 children or more) had higher mitochondrial lesions (8-oxodG) than women whom had no kids. This was also demonstrated with high sexual output, which is costly. Flies that are 'hyper active' die the quickest (they become slow and can't fly anymore, then just perish there). There is such a thing as 'burning the candle by the 2 ends' (resource wise). Women would live longer than men Precisely Because they would put Less resources in sexual reproduction (such as in men do whom have sperm for their entire life), and more into Somatic Tissue maintenance - evolution chose female gender as indispensable, male gender dispensable; one woman is limited by number of kids she can make in certain amount of time; while a man can impregrante many women very rapidly (which constant sperm), women have set fixed number of eggs and most deal with those limits. IT means that evolution chose female gender for 'being there longer - to insure that kids happen', if she dies, specie dies. Thus, it is important that she lives the longest possible and in that time span, she can make kids one after another (for a period of time until menopause arrives).

It makes sense that male would be sexually capapble for whole life while female wouldn't; the net effect being short male life (since as said sexual resources take away from somatic ones);
long(er) female life. Just a 2 cents.

PS: In any case, the whole purpose of rejuvenation is attaining that neotenous body once again, being 'immature' once more (like that teenager body again, that is True rejuvenation and so far, only epigenetic signature erasing could achiever this dramatic, not just damage reduction).

Posted by: CANanonymity at October 12th, 2018 4:47 PM

My bet is that it is male human longevity that caused an increase in overall human longevity. Remember, we live quite a long time for a primate. I think that older males, reproducing later in life, caused the spread of "longevity genes" that made humans live longer, and that human females benefitted from this selection incidentally. (I have forgotten the term for traits that are shown by both sexes, but which benefit only one sex - sorry).

The fact that women live longer than men is due to two factors. First, the same genes that enhance life expectancy, despite the negative effects of testosterone on immune function and longevity in males (both well documented), cause greater life expectancy when that hurdle is removed. The second factor is, I believe, related to the stress of multiple pregnancies in our natural population (upwards of eight pregnancies being not uncommon). Like birds, who live longer than expected given their body size and heart-rate, but do live longer due to improved self-repair, women had to evolve improved self-repair rates in order to reproduce adequately.

Posted by: Benjamin Wade at October 12th, 2018 7:31 PM

@Benjamin Wade: Because of that reason I have encouraged my friends to reproduce at higher ages despite the government saying the opposite. They fear problems with fertility for women at higher ages. I say: Use assisted reproductive technologies (ART).

Posted by: thomasa at October 13th, 2018 7:15 AM

@thomasa
Regardless of the PAC effect, the paternal age effect is deleterious and at the present time assisted reproductive technologies will not guard against the types of diseases and disabilities that the paternal age effect can cause. If males want to delay reproduction due to economic or social reasons, frozen semen is a practical option. Technology has pretty much done away with human evolution via natural selection and has enabled directed evolution. I expect that by the time we can fix the problems caused by the paternal age effect, we will be able to engineer in longevity.
https://www.fertstert.org/article/S0015-0282(10)02417-9/fulltext
https://www.ncbi.nlm.nih.gov/pubmed/26055426

{OTOH, perhaps the world could do with more autistic people in it. }

Posted by: CD at October 13th, 2018 1:39 PM

edits:
PAC effect = paternal age at conception effect on telomere length
frozen semen = sperm banking

Posted by: CD at October 13th, 2018 1:43 PM

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