"Male enhancement" and reproductive senescence
Three products that profit on male insecurities (Enzyte, Viagra and Tiger Penis Wine)
In my earlier post The Evolution of Menopause I discussed how accumulating evidence suggests that reproductive senescence in women is an adaptation promoting inclusive fitness. In response Stew asked the question:
Where does this leave the so-called “male menopause”? . . . Is male menopause a real phenomenon, and if it is what could its benefits be to survival?
I confess that I had never even heard of male menopause before, so this question intrigued me. A quick Google search revealed an onslaught of online “health” sites ready to sell me a host of products to fight this, previously unknown, affliction. These ranged from “new super potent herbal formulations” to “pure potent 200:1 Tongkat Ali Extract” (whatever the hell that is) to the more general “Ultimate Male Potency Booster”. I think I’m noticing a trend in their advertising approach.
Even Harvard Health Publications announces “Is There a Male Menopause: Will Hormones Help?” Apparently we don’t even need to know if there is an actual problem before jumping to an expensive cure. However, after a great deal of discussion about the slow decline of testosterone in men after the age of 40 the good doctors state:
“A 1% yearly drop in testosterone production is imperceptible at first, but by the age of 70, the average man’s testosterone production is 30% below its peak. . . . Despite the obvious appeal of testosterone replacement for older men, most doctors advise against it.”
Their prescription: eat a balanced diet and get more exercise.
So while male menopause seems to have more to do with men’s desire to be 25 forever and less to do with an actual physiological condition (remember, in women menopause is a rapid event that is confined to a specific age window) there is something to this evolutionary question. Why do men undergo a decline in testosterone at all? If evolutionary fitness means leaving the most offspring, wouldn’t the 90-year-old with the enormous Enzyte grin be the ultimate example in "survival of the fittest"?
The answer has to do with life history theory, or evolutionary cost-benefit analyses. Testosterone has numerous behavioral effects, not least of which are risk taking and aggression. Writing in the journal Evolutionary Anthropology, Richard G. Bribiescas shows how among Ache foragers in Paraguay male reproductive value (i.e. what women want) is greatest between the ages of 18 and 30. During this period, Bribiescas euphemistically notes, “males exhibit an acute spike in mortality.”
In other words, males are willing to take excessive risks (or, in rare cases, even take someone out) in order to have a better shot with the ladies. It is during this same period that male testosterone is at its peak. However, it probably wouldn’t be in an individual’s long-term reproductive interests if they continued such behaviors once they were a successful father or grandfather. As it turns out, this is the pattern seen in many other species.
Human male senescence exhibits characteristics that are like those that occur in most mammals. As in other primates, human gamete production is continuous, robust, and relatively invariant with age. However somatic deterioration seems to reflect changes in investment away from reproductive effort to survivorship.
So the evolutionary strategy has been to invest heavily in reproduction during early adulthood and then to focus on yourself and your children in later years. So perhaps testosterone declines over time because in those individuals where it did the end result was having more children with those same genes than in the men who continued to display risky behaviors. While our culture encourages men to be young forever, our evolutionary history suggests this is ultimately a failing strategy.
As for male menopause, there doesn’t appear to be much to it. However, the obsession with male potency has long been a successful marketing ploy. In the Victorian era men would pay to have regular injections of crushed goat testicles and in cultures around the world men imagine that eating the reproductive organs of other animals will somehow provide power to their own. It’s all a load of hooey. But, at least with the “super potent herbs” you might get some of the vitamins that Harvard’s health specialists recommend.
Richard G. Bribiescas (2006). On the evolution, life history, and proximate mechanisms of human male reproductive senescence. Evolutionary Anthropology 15(4):132-41. doi: 10.1002/evan.20087