Zebrafish could answer why some women prefer older men

London, Feb 27 (ANI): A scientist in New Zealand has turned to zebrafish in an effort to find out why some females are attracted to older males, and is spending thousands of dollars on the study.

According to Stuff.co.nz, research fellow Dr Sheri Johnson at Otago University, New Zealand, is putting a 345,000-dollar grant towards finding out, using of 700 zebrafish, the Daily Mail reported.

For years many people have argued a female tendency to be attracted to older males, goes against evolution as older men have a decline in sperm function and the chance of a birth defect also increases with age.

Zebrafish have been selected because they fertilise their eggs externally, making the process easier to mimic, according to the scientist.

Aside from ethical issues, Dr Johnson said trying to run the study in humans and controlling all of the variables would be too difficult.

She cites one human study, which was a cross-cultural comparison done in the 1980 and the results, indicated that women's preference for older men was related to their tendency to have accumulated more attractive resources called 'resource acquisition.'

Dr Johnson said that seems a relatively obvious attraction and even makes evolutionary sense in terms of safety and protection.

"But if a woman was coming to the end of her fertility window and she wanted to get pregnant and needed a sperm donor, she would definitely choose a young male over an older one, right?" she told the news website.

She noted studies show a marked differences in semen volume, sperm motility and morphology in men in their thirties and fifties, which means they should be less attractive to women looking to have a child.

Increasing male age has also been linked to a number of medical complications, such as miscarriage and higher rates of autism and Down's Syndrome, said Dr Johnson.

But the number of men between 35 and 49 years old fathering children had increased in the past few decades, according to Stuff.co.nz.

John Peek, group manager of Fertility Associates, said a man's age did increase the chance of a cell disorder, but not as much as a woman's age.

"Jumping 30 years in the male's age - from 20 to 50 - might be the equivalent of jumping two or three years in a woman in her late 30s," he said.

Peek said Dr Johnson's study could be very useful as current knowledge was based on indirect evidence and small samples sizes.

"There's going to be a bit of a difference between tiny little fish and people but it's a lot clearer if you know what the basics are and you can say 'OK, what might be different between zebrafish and humans?' rather than saying we don't actually know the fundamentals at all," he added. (ANI)