Hard wired 22: Kin selection

As we know there is much, much more to reproductive fitness than merely having sexual intercourse. We increase our chances of reproducing by ensuring longevity (dead animals don’t breed), by increasing social status for males (high status males fertilise more females) and by ensuring effective nurturing in females (dead babies are an expensive waste of biological resources). If that last sentence seems sexist it’s because it is – at least it is by modern standards.

Pleistocene family groupRemember that our evolved traits and tendencies didn’t arise in the modern world – they evolved in the Environment of Evolutionary Adaptation (EEA) otherwise known as the Pleistocene era. This is the period that began around 2.5 million years ago with the arrival of Homo erectus and ended around 12,000 years ago. The Pleistocene predates civilisation as we know it today with the first cities only arising between 7,000 and 10,000 years ago, let alone modern notions of sexual equality. What seems sexist today was less of an issue then.

The adaptive division of labour along gender lines would have been much less problematic than it is today. The differences between men and women so strenuously denied by some in today’s world evolved precisely because they helped our species to survive and thrive in the distant past. Small bands of hunter gatherers engaged in a constant battle against predation, starvation and the elements had little time to worry about the perceived unfairness of gender divisions. Indeed – the only divisions they were likely to consider were around kin and tribe. Little else matters very much in small, interdependent, subsistence economies. So for now we’ll talk about male status and female nurturing. Later we’ll consider the proprietary attitude of males to females, the constant male paranoia relating to cuckoldry and the remarkably unfair sexual double standard that leads to the remarkably irrational ‘Madonna/Whore dichotomy’. But for now we’ll keep it simple.

  • Strong, high status males get more sex.
  • Chaste, nurturing females get more male parental investment for their kids.

Add to this a simple equation about relatives and we have the basis of mutual co-operation within family groups (tribes) intended to boost genetic fitness among those who share genetic material at the expense of those who do not. It’s important to remember that there is no need for individual Homo erectus, Homo habilis, or even Homo sapiens consciously to calculate these odds. They simply need to behave as if they had and that’s where emotions come in. Natural selection favoured those Hominids who favoured relatives because their genes survived more often than the genes of Hominids who did not.

The equation is based upon genetic closeness and it works like this….

  • I carry 100% of my genetic material.
  • My son or daughter carries half of my genetic material.
  • My brother shares approximately half of my genetic material.
  • My brother’s son or daughter carries approximately a quarter of my genetic material.
  • My nephew’s son or daughter carries approximately one eighth of my genetic material.

Since natural selection favours those animals who protect their own genetic material it makes sense for me to favour my closest relatives (in descending order) before I even consider helping those not directly related to me. Consequently, by favouring close relatives (even without understanding the genetic calculation) I make it more likely that my own genetic material will survive. As more of that genetic material survives (inevitably at the expense of the genetic material of those Hominids who do not survive) the species moves more and more toward a bias of helping relatives until eventually there is nobody left who thinks differently. Once this universal saturation of aiding relatives is reached the practice of favouring relatives can be described as a part of ‘Human nature’.

This is why females are more likely to nurture, adopt or share the care of close relatives than the children of strangers.

This is why men are more likely to defend the ‘honour’ of female relatives (even committing murder) than that of non-related women.

This is also why step-children are significantly more likely to suffer neglect, abuse or even murder at the hands of step-fathers who would otherwise be expected to expend their parental resources nurturing somebody else’s genetic material.

This whole process of favouring relatives for special consideration is known as kin-selection. It’s one of the evolutionary forces that leads to loyalty (in this case family loyalty) and is expressed in less formal language with maxims such as….

“Blood is thicker than water” or

“Charity begins at home”.

The fact that this kin selection has nothing to do with the personal qualities or deservingness of the relative to be helped is irrelevant. The deciding factor is genetic closeness. That’s what natural selection favoured and that’s what we’re stuck with today. We’d rather see a deserving stranger starve to death than a thoroughly unpleasant relative, especially a close relative. That may not be particularly fair or rational but it is the most viable option for our genes and that, in the final analysis is all that matters for natural selection purposes.

About Stuart Sorensen

Nurse, writer, blogger and witterer. I work full time delivering care and wittering at people all over UK. It's great if you like the sound of your own voice (and I most certainly do). You can find me at http://www.stuartsorensen.wordpress.com or at http://www.thecareguy.com
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2 Responses to Hard wired 22: Kin selection

  1. Scout says:

    Really enjoying the series, it’s so refreshing to see this information widely available and in an easily digestible form.


    • Stuart Sorensen says:

      Thanks Scout, that’s good to hear.

      My only concern is that in making what I’m learning accessible I’m also risking making it a tad too superficial. Still – if people prefer to read more in depth they can always go and read the research articles themselves. I’m just teaching myself in overview through the blog really.

      It’s good to know you’re enjoying it.




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