Old men and even older women
With progressive advancements in healthcare and proper nutrition throughout the world, the human race has transgressed the bounds of average life expectancies. If one were to look at our species at today, it would be observed that women have now come to considerably outlive men.(6) When women reach midlife, usually ranging anywhere as early as 45 to 55 years of age, they begin to experience menopause. It is defined as the time when a woman’s ovaries fail to produce viable eggs and consequently cease to generate estrogens, progestin, and testosterone. These hormones were once readily used in monthly reproductive cycles and its absence collectively ends a woman’s natural fecundity. This part of a woman’s life prevents them from directly taking part in the most primitive goal all living organisms attempt to achieve, that being surviving long enough to reproduce and carry down their genetic information to the next generation before they die.
Looking at elderly woman on a strictly genetic standpoint, they would deem to be rather dispensable. It seems as though man’s ability to force its species to live longer leaves women in a postmenopausal life that renders no evolutionary benefit. For the symptoms associated with menopause include, but are not limited to hot flashes, palpitations, mood swings, sleep disturbances, depression, anxiety, urogenital atrophy, lack of concentration, and osteoporosis, (2) making them more vulnerable to predation. But despite all of these disadvantages, older women still manage to live well past the 100 year mark. Because of this, it seems as though there should be some underlying evolutionary importance in women experiencing midlife and postmenopausal life.
Now the counterpart of menopause in women, which is commonly misinterpreted as a part of a midlife crisis, is called male menopause or andropause. This occurs in men at around the same age it does for women and involves a gradual decrease in testosterone levels and therefore reproductive ability. Men at this stage in their lives also experience impotency, inability to sleep, night sweats, and reduced bone density but the main difference between the two is that andropause functions more as a phase for men, they come out still capable of reproducing. (3) This evolutionary bias questions the logic behind limiting a woman’s reproductive ability but not a male’s.
What possible benefit is there in favoring older women to live long, infertile lives and men to shorter promiscuous ones with young girls? For the sperm made today is not the sperm made tomorrow. As men age, the probability of their sperm having more genetic abnormalities increases, ultimately increasing the likelihood of producing an unhealthy offspring. (4) Why should life allow these men to continue being sexually potent if it leads to more “less fit” kids in the next generation? A potentially good story to justify this is that with the increase in DNA fragmentation that will be carried down to the offspring, more genetic “defects” will be introduced into the next gene pool, which in essence opens the world to more possible variation for the human race to be composed of.
As women get
progressively older, they increase the odds of bearing children with a specific
genetic abnormality called Down syndrome. (4) Now if only women of older age
could continue to naturally bear children there would be more women that could
have children with these men that are passed the age of 40, increasing even
more so the amount of extreme variability in the next generation. Only here can
we see a potential synergy between older men and older women reproduction
because of the higher chances of mutation it would give rise to.
But women who either start or continue to give birth during the second half of their lives are more susceptible to miscarriages and risks that would put not only her but her child in danger. Eencephalization, the amount of exceeding brain mass in proportion to the total body mass of the animal, renders relatively large neonatal brain sizes which forces the uterus to be enlarged and weakens the abdominal muscles. This holds especially true when combined with multiple successive deliveries and results in repeated exposure of infectious diseases, atrophy of the endometrium and irregular positioning of the fetus. (5) Even if the child does survive the many repercussions of later pregnancies, it is less likely that s/he will be able to survive the mother’s immediate or soon to be timely death. For this reason, maybe it is not necessarily a disadvantage that woman eventually cease to reproduce after a certain age.
So what is a woman suppose to do with an entire other half of her life ahead of her? One theory that has been purposed is called the grandmother hypothesis in which all of the energy that was once reserved for procreation is used instead for the continued raising of her children and grandchildren. (7) This works to redefine elderly women’s role in a society that is filled with an extreme altriciality in its children and inexperienced caretakers in its men. This additional help can be advantageous because the survival of a man’s offspring, essentially his genes, depends greatly on the well being and longevity of the mother of his children. (6) If there are more mothers in the equation, the better the chances are that past genes will be preserved for the future.
5. Eckart Voland, Athanasios Chasiotis, Wulf Schiefenhevel Grandmotherhood. New Jersey: Rutgers University Press, 2005