The Ape that Understood the Universe: How the Mind and Culture Evolve by Steve Stewart-Williams

Author:Steve Stewart-Williams [Stewart-Williams, Steve]
Language: eng
Format: azw3, epub, mobi
Publisher: Cambridge University Press
Published: 2018-09-12T16:00:00+00:00

A promising start. But how could you get your vehicle to reliably target such individuals? There are several ways, but the most important is that you could get your vehicle to target its genetic relatives. Kin! Your vehicle’s kin are more likely than anyone else in the world to possess copies of you, as a result of their recent shared ancestry. As such, by programing your vehicle to be nice to its relatives, you could potentially increase your representation in the gene pool. Importantly, your vehicle’s kin are also more likely than anyone else in the world to possess copies of every other gene in your vehicle’s genome. For that reason, those other genes would probably have no objection to your nepotistic masterplan, and some might even jump on the bandwagon and help you to achieve it.

This brings us to one of the most important building blocks of Hamilton’s theory: the coefficient of relatedness, also known as r. This is a metric which expresses the degree of genealogical relatedness between two organisms. There are several definitions of r, but for present purposes, the most useful is that r represents the probability that two organisms share any given gene as a consequence of recent shared ancestry. That’s quite a mouthful, so let’s break it down into bite-size pieces. The simplest case concerns relatedness between parents and offspring. Parents pass on half their genes to each of their children. That means that there’s a 50 percent chance that any given gene in the parent’s genome will be copied into any given child it produces. And this means in turn that relatedness between parent and child is 50 percent – or to put it in technical terms, r = .5. To work out r for grandparents and grandchildren, we simply perform this operation twice. There’s a 50 percent chance that the grandparent passed a given gene to the parent (its child), and then a further 50 percent chance that the parent passed the same gene to its own child, the grandchild. Thus, relatedness between grandparents and their grandchildren is 50 percent of 50 percent, or 25 percent (r = .25).

Things get more complicated for non-descendant kin. For half-siblings (who share one parent), there’s a 50 percent chance that the shared parent passed a given gene to one sibling, and a further 50 percent chance that the shared parent passed the same gene to the other. Thus, the chances that both inherited a given gene from the shared parent is 25 percent, and relatedness between half-siblings is .25. For full siblings (who share two parents), there’s a 25 percent chance that both inherited a given gene from one shared parent, and another 25 percent chance that both inherited it from the other shared parent. Add these together and you find that there’s a 50 percent chance that both inherited a given gene from either one of the two shared parents. Thus, relatedness for full siblings is .5.

Without going into all the details, it’s possible to crank out relatedness values like this for any family members you care to name.

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