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While inbreeding is fairly common in the animal kingdom, in most human societies the practice is banned.

Despite this, a new study suggests that ‘extreme inbreeding’ (EI) - in which parents are first- or second-degree relatives - is much more common that thought.

In the study, researchers from the University of Queensland analysed data from the UK Biobank, which contains genetic information from around 450,000 participants of European ancestry.

Because inbreeding is banned in the UK, people are often reluctant to self-report it.

(Image: Getty)

However, because the Biobank contains genetic information, the researchers could use this data to estimate extreme inbreeding, instead of relying on self-reports.

Their analysis revealed 124 cases of extreme inbreeding - a rate of one in 3,652.

Unsurprisingly, this number differs hugely from police incest reports, which indicate a rate of one in 5,247.

Delving deeper into the data, the researchers then looked at the health histories of those individuals, and compared them with the general population.

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The comparison revealed that people who had been born out of extreme interbreeding were on average slightly shorter, less smart, and less able to reproduce.

Worryingly, they were also more likely to have lung problems, and more likely to contract diseases.

In their study, published in Nature Communications , the researchers, led by Loic Yengo, wrote: “Altogether, our findings suggest that the prevalence of EI in the population is small and that very large observational studies are required to quantify it accurately.”