Why parents think your partner isn't good enough

The study, involving a University of Bristol researcher and published today in the journal Evolution & Human Behavior, shows that this conflict over mate choice may be rooted in an evolutionary conflict over resources.

Dr Tim Fawcett, a research fellow in Bristol's School of Biological Sciences, teamed up with scientists at the University of Groningen to investigate how the mate preferences of parents and children co-evolve. They found that parents tend to give more resources to children whose partners provide less support, and that this leads to a conflict over mate choice.

The team built a computer model to simulate the evolution of parental behaviour when their daughter is searching for a partner. The model shows that, typically, parents should prefer a son-in-law who is more caring and supportive than their daughter would otherwise choose.

Dr Fawcett said: "The conflict over parental resources is central to understanding why parents and children disagree in mate choice."

The model predicts that, when parents distribute resources equally among their children, their mate preferences should coincide exactly. But when parents contribute more to children whose partners invest less, a conflict arises.

Dr Fawcett explained: "Parents are equally related to all of their children, whereas children value themselves more than their siblings -- so each child wants to get more than their fair share of parental resources." This means that the children are willing to settle for a mate who is less caring than their parents would ideally like.

The new theory, if correct, sheds light on an intriguing aspect of human behaviour and may help to explain patterns of variation across cultures. Piet van den Berg, lead author on the study, said: "Our model predicts that the conflict will be stronger when fathers rather than mothers control resources, but this remains to be tested."

In future work, the scientists plan to investigate preferences for different aspects of quality. "Surveys show that children tend to place more importance on physical attractiveness, smell and sense of humour, whereas parents care more about social class and family background," said Mr van den Berg. "We don't yet understand the reason for this difference, but it probably has something to do with our evolutionary history."