Sunday, December 20, 2009

Tiger Woods, Polygamy and Charles Darwin

At Christmas lunches everywhere, it has been inescapable no doubt to avoid a discussion about the extra marital affairs of golfing legend Tiger Woods. Such is the following of this athlete that the media has been relentless in pursuing new leads to this story.

At my Christmas lunch with fellow work mates, it inspired such robust conversations that it got me thinking about and investigating the theme of polygamy. According to Ted Bergstrom, the topic is more than just a curiosity. Of the 1170 different societies that have been ethnographically classified, 850 practice polygamy. The so-called marriage market in polygamous settings has been theoretically modelled by Bergstrom. He states that
(i)n human societies, males who inherit economic wealth from parents or other relatives can increase their reproductive success substantially by acquiring additional wives, mistresses, or concubines. For females, on the other hand, an extra husband adds little to her lifetime fertility. Once a female has achieved moderate prosperity, additional wealth does little to relax the biological constraints on the number of offspring she can have.
Aside from ensuring the propagation and extension of his genes to subsequent generations, research has uncovered another benefit: longevity for the male. Ewen Callaway in the New Scientist wrote last August that ecologists from the University of Sheffield, have found that
men aged over 60 from 140 countries that practice polygamy to varying degrees lived on average 12% longer than men from 49 mostly monogamous nations (...) The explanation could be both social and genetic. Men who continue fathering kids into their 60s and 70s could take better care for their bodies because they have mouths to feed. But evolutionary forces acting over thousands of years could also select for longer-lived men in polygamous cultures.
There are of course possible pitfalls in the scoring method adopted for measuring polygamy among societies, something which admittedly could be improved for future research, but this finding is interesting considering that this year marks the bicentenary of Darwin's birth and the 150th year since he published On the Origin of Species which details his theories on evolution.