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Economic theory assumes we are all selfish. Everything we do, we do it just for ourselves. There is no such thing, in their theory, as altruism.

It is odd, because if you ask many entrepreneurs what motivates them, chances are that they will say that in addition to making money, and wanting independence, they have a desire to in some way change the world for the better.

It may be that it is in their genes. Richard Dawkins explained the theory in his seminal book, The Selfish Gene.

And that bring me to a row that broke out in the midst of the battle to become the next leader of the UK Tory party, and thus Prime Minister. In an interview with The Times, one of the two candidates, Andrea Leadsom, seemed to suggest that she had more of an interest in building a prosperous future as she had children, unlike her rival for the position, Theresa May, whose stake in the future resided in her being an aunt.

Now it may be that Ms Leadsom didn’t quite mean it like that. But it is worth considering this argument anyway.

And to illustrate the point, let’s use an anecdote.

The evolutionary biologist JBS Haldane was asked, or so goes the story, if he would give his life to save his brother. He was in a restaurant at the time, and he is supposed to have grabbed a napkin, and after making some furious calculations said “No, but I would to save two brothers or eight cousins.”

One of the men who was influenced by Haldane, WD Hamilton, “showed mathematically that, because other members of a population may share one's genes, a gene can also increase its evolutionary success by indirectly promoting the reproduction and survival of other individuals who also carry that gene.”

The idea has several names, Inclusive fitness, kin theory, or kin selection theory.

Richard Dawkins looked at this very idea. The gene wants to see as many copies of itself as possible. But it also compromises and settles for seeing as many close copies as possible. That is why we accept sharing our genes with another person when we have children. Evolution has made it so.

Inclusive fitness, by the way, explains why bees are willing to commit suicide to save the rest of the hive, to save the lives of their brothers, sisters, half-brothers, half-sisters, and future nieces and nephews.

But we are all related to each other. Geneticists have found that all humans have a common female ancestor who lived some 150,000 years ago.

Our genes are similar; our DNA is very similar.

Evolution has hardwired us into wanting to support our fellow humans, and the more closely related to us they are, the more we want to support them. It may make sense to give our lives to save two brothers or eight cousins, but it would surely, from an evolutionary point of view, make sense for us to act in the interest of 60 million countrymen, countrywomen, and the hundreds of millions yet to be born.

Of course, in reality, it does not work quite like that. We do not interpret these things perfectly. Our brain takes short cuts, and substitutes proximity for genetic relationship. That is why people care deeply for their adopted children, and why immigrants can care about the country they have migrated to.

And why a childless prime minister has a massive genetic stake in the future of her country.

By Michael Baxter, economics writer, author and entrepreneur