Let’s be honest, you hate your daughter’s boyfriend. Don’t you? You’ve tried to rationalise it, you want to be supportive, but anyone can see he’s just not right for her.

You have tightlipped conversations about it with your friends (“Well, she seems happy. I’m just glad she’s happy”); you write down ideas for crushing remarks in a notebook you keep by your bed (“Sean, how are you? Sorry... Steve...Stan! I knew it was Stan.”) You embed strands of his hair in small wax statues, and burn them at the equinox. You have attempted murder twice.

There are many, many online forums devoted to talking about sons- and daughters-in-law, and the unsuitable choices of your children. There is a lot of angry content (the above was just a brief precis). But it’s odd, really, in evolutionary terms, that more people don’t approve of their children’s partners. After all, parents and their children are rooting for the same set of genes. They should go for pretty much the same people. Why don’t they? Why is tension with the in-laws such a cliche?

Two scientists have come up with an evolutionary argument. In a study published in the journal of Evolution and Human Behaviour, Franjo Weissing and Bram Buunk argue that it all stems from children trying to get money out of their parents.

To show this, they built a computer model detailing a vast fictional population. The men had different abilities to provide for future children, and women had varying strengths of preference for this trait. Children of the pairs who got together would inherit their characteristics (with a few mutations). There were a couple of other variables, too. Parents could influence choice, and could also divide their property between their children any way they wanted.

As the (admittedly very sexist) model ran through many thousands of generations, the scientists noticed that parents allocated their resources unequally. They were giving more to the daughters with less supportive mates.

This makes total sense for the parents - this way, they ensure the survival of the largest number of grandchildren. It presents the daughters with a bit of a dilemma, though. If they go for Mr Perfect, their sisters end up with the lion’s share of parental support. It’s a real effort to fight for Mr Perfect, too - using up a good deal of their own resources. What to do?

Over generations, the daughters started to choose flakier, less caring partners, knowing their parents would help them out in return. To balance this, the parents started desperately encouraging them to go for someone more reliable. And this is where the classic tension started.

So it’s not your fault that you hate your daughter’s boyfriend. Just try not to murder him, as it’ll be hard to hide. The motive’s already there, you see, clear as day, written in the genes.