A new study has revealed that cougars are driven by biological programming rather than by lust to select a younger male partner for them.
The study has revealed that women over 40 who have in-vitro fertilisation are far more likely to conceive with a much younger man because young sperm "corrects" their old eggs, while the same applies for older men choosing young "trophy wives" - whose young eggs correct defects in old sperm, Stuff.co.nz reported.
Researcher Michael Dahan, of Montreal's McGill University, said that it actually gives a biological argument for the cougar phenomenon of an older woman selecting to be with a younger male.
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The researchers, who analysed data of 631 women in their 40s undergoing 904 cycles of IVF, found the age of the male partner was a strong predictor of success because, once a woman hit 40, her eggs were less able to correct DNA defects in sperm and older women's chances of having a baby plunged once their partner reached an average age of 43.5, much younger than in previous studies, which found a deterioration in sperm quality for men aged over 50.
New technology found that DNA in sperm became "more fragmented" as men aged, which was why the fertility clinic stopped accepting donors aged over 45.