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Scientists explain why people often choose life partners with the same height, weight and intelligence

The chances are that you’re going to marry someone a lot like you.

They’ll be of similar height and body weight. They’ll look a bit like you.

They’ll even be of similar intelligence.

This doesn’t happen by accident. We actively seek out similar people.

And our choices of life partners are shaping our genomes.

Why are we seeking out similar people for our life partners?

These are the conclusions presented in a research paper published recently in Nature Human Behaviour.

Matthew Robinson was the lead author of the study. He’s a postdoc in the lab of geneticist Peter Visscher at the University of Queensland in Brisbane, Australia.

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Robinson and his colleagues analysed large databases that included information on human physical and genetic traits.

They focused on genetic markers for traits such as height and body mass index (BMI) to predict the height and BMI of that person’s partner.

The scientists performed the calculations for more than 24,000 pairs of husbands and wives of European ancestry and found a strong correlation between the predicted height of people’s partners and their actual height. They found a similar correlation – but slightly weaker – between people’s genes for BMI and the actual BMI of their partners.

Their conclusion:

People had actively chosen partners with similar genes to themselves.

This is sexual selection at work

This is evidence in humans of assortative mating, which is a form of sexual selection.

It’s been witness widely in nature. For example, it can be seen when more brightly colored bluebirds mate with each other and duller colored bluebirds pair up. Another example is when smaller Japanese common toads mate, whereas the larger ones stick to themselves.

Researchers have suggested that assortative mating increases relatedness in families, giving offspring a better start in life.

Assortative mating happens with education

The researchers also tested for assortative mating in years of education in 7,780 couples in a UK database.

They found a remarkably high degree of correlation between predicted similarities in education levels and actual similarities in education levels.

According to Robinson, it likely implies that people select mates for similar interests, which are strongly associated with level of education.

Mate choice “affects the genomic architecture of traits in humans”

Robinson says that assortative mating increases the chance that selected traits will be passed on to offspring, affecting the genomic architecture of traits in humans.

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Their findings have implications for genetic models that predict the prevalence of traits such as schizophrenia.

The reason is simple:

New research suggests that people with autism, schizophrenia and attention deficit hyperactivity disorder tend to marry each other.

Robinson’s research will help to see whether these choices are also rooted in DNA.

Closing thoughts

This research was a little surprising to come across.

I remember reading about the philosopher Schopenhauer’s theories about mate selection, and some of the insights have stuck with me since.

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Schopenhauer believed we select mates based on compensating for our physiological and psychological deficiencies.

(Interested in exploring Schopenhauer’s ideas? Check out these Schopenhauer quotes.)

Why?

Because our offspring will have less chance of having these deficiencies.

In my case, I have an abnormally long body compared to my legs. Therefore, I would likely be attracted to a lady with long legs.

This checks out.

This probably quite a trivial example. But you can apply it more broadly. For example, I’m not such a nurturing person and would select a partner who is.

Yet the research reported on above provides a different emphasis to mate selection.

It suggests that we are looking for similarities between partners.

This would contradict my previous understanding about searching for people who are physically differentiated to me.

What do you think of this research? Does it match your own personal experience? Let me know in the comments below. We’ll even update the article with anecdotes you share with us!

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Written by Justin Brown

I'm Justin Brown, the founder of Ideapod. I've overseen the evolution of Ideapod from a social network for ideas into a publishing and education platform with millions of monthly readers and multiple products helping people to think critically, see issues clearly and engage with the world responsibility.

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