It has been a while since I last posted anything here. Part of the reason is that since I arrived to Dundee i haven’t had access to my print issues of Science and haven’t had the time to read Nature and other journals online. Still, this morning I was browsing an issue of the Economist in which they mention this article in this week’s edition of Science.
This research tries to answer the question of why is it that in richer (wealthier) human societies, families have on average fewer children. Although people have put other reasons, based mostly on sociology, the explanation these researchers favour is based on genetics. In general, and from the evolutionary point of view, it is a good thing for an individual not inbreed. Having to many genes in common with your partner means that the offspring will inherit virtually the same copy of all your genes, be them good or bad. Looking farther afield for your partner would likely result in offspring with a more diverse set of genes which means that at least a subset of your children have a good chance of having a rather good genetic mix.
Wealthier societies tend to be also technologically more sophisticated and people are more likely to meet (and mate) with individuals who live farther away and whom which they share a smaller number of genes. Now, some diversity in the gene pool is a good thing but too much of it can be too much of a good thing. As the parents share a smaller share of the same variants of the same genes the number of genetic incompatibilities increase and the fertility rate decreases.
The conclusion? if your goal in life is to maximise the potential success of your genes to live on in future generations then you might do good to consider distant cousins when planning your family.