Friday, October 26, 2007

Polygyny and why male live shorter

Take the life expectancy statistics of any species. For most species, including human, female live longer than male. Among many theories, my favorite one (at least for human) is "male is the defect version of female." Remember that male have the XY chromosome, while female have XX. The Y chromosome is a 'mutated' version of the X - means that boys are by nature mutants (the 'defect' version of girls). That makes boys are more prone to death, which explains the higher rate of postnatal mortality rate.

A new research, cited in this article, offers another perspective: polygynous practice leads to shorter male life expectancy . According to the article:
In 16 of the 19 polygynous species in their sample, males of all ages were much more likely to die during any given period than were females. Furthermore, the older they got, the bigger the mortality gap became. In other words, they aged faster. Males from monogamous species did not show these patterns.

The point about polygyny, according to Dr Clutton-Brock, is that if one male has exclusive access to, say, ten females, another nine males will be waiting to topple the harem master as soon as he shows the first sign of weakness. The intense competitive pressure means that individuals who succeed put all their efforts into one or two breeding seasons.

The implication for human is:
Dr Clutton-Brock reckons that the sex difference in both human rates of ageing and in the usual age of death is an indicator that polygyny was the rule in humanity's evolutionary past—as it still is, in some places.
Well, at least it adds to the debate on the good and bad side of polygyny.


  1. "The Y chromosome is a 'mutated' version of the X - means that boys are by nature mutants (the 'defect' version of girls)"

    just to be clear,
    mutation is neither bad nor good. if a mutant turns out to be more adapted to the environment then it's good for them.

    i'm just helping my significant other's effort to correct common misperception on this matter. :D

  2. Hehehe... Roby, of course you and your significant other are correct. Even there are other theories refuting the theory that XY chromosome leads to lower life expectancy.

    Just thought that the XY theory may please the man-heater manager :-)