Kissing cousins ‘have more kids’
So I found this random and interesting piece on the BBC website. The part that peaked my interest was the following passage.
The researchers wrote that the shift from smaller, rural communities to large cities – a feature throughout the modern world, was “a new situation for humans in evolutionary terms”.
If “kinship” did offer an advantage, they said, then urban living, which reduced the chances of close cousins becoming partners, could slow the birth rate.
This is probably only a revelation to someone with so little knowledge of demography and biology, but it is fascinating, isn’t it? And it makes so much sense if one takes time to think about it. Until relatively recently the vast majority of humanity would have been fairly immobile, rooted in a particular locality for most of their lives. Even in the vast empires that existed sporadically through human history, most of the population would have lived in their villages and perhaps traveled to the nearest town, but that would have been the extent of their travels.
With the exception of princes and nobility, there would have been little marrying of partners who did not live relatively close together. If that was the normal state of human existence for much of history, then it makes sense that traits which favoured mating between distant cousins would have conferred an evolutionary advantage and prospered as a result.
This evolutionary process would have taken thousands of years to reach the point we are at now. Compared to that, the dramatic urbanisation we have experienced over the last couple of centuries is a very short, sharp shock. It’s not the sort of change humanity can rely on evolution to sort out. At least not for a very long time.
The two most obvious observations that strike me are that this could explain a large part of falling fertility of wealthier societies, and not so much the changing life-style of modern living, as has been assumed. The other is that the increasing urbanisation of China could have a larger impact on reducing the population than the one-child policy achieved. (Of course, in China’s case, the huge gender imbalance caused by the patriarchal cultural bias of that society is also having a growing effect on their population’s fertility.)
Before anyone gets carried away, there’s nothing in the study to suggest that we’re all going to die off as a result. There doesn’t seem to be any cataclysmic fall in fertility and there are well over 6 billion of us around. But, a definite fall in fertility could be an inevitable result of urbanization for all countries as they develop economically. The only way developed countries seem to have been able to cope with the economic and social consequences of this fall is immigration.
And that will be the subject of a post on another day, since I have studying to do.
