Two new dating websites have confirmed that infidelity is on the rise in Australia, with more 293,000 people signing up for their services.
More than 280,000 people, 36 per cent of them women, have signed up at ashleymadison.com since it was launched three weeks ago, and about 13,000 people have visited gleeden.com in its first week.
They follow the basic structure of most dating sites, where members publish profiles outlining their interests, passions and sexual proclivities.
But instead of singles, the pay-to-join sites specifically cater for married people looking for secret dalliances or long-term affairs.
"It is not in anyone's DNA to stay with the same person," the Sydney Morning Herald quoted ashleymadison.com founder Noel Biderman as saying.
"So this notion that (our site is) generating this kind of behaviour is wrong," he said.
American TV host Dr Phil McGraw agrees. Last week, the clinical psychologist known as Dr Phil told female viewers how to tell if their man would cheat on them.
He said men with a ring finger longer than their index finger have higher testosterone levels and were more likely to cheat. He also said that men with a short gene, the vasopressin receptor gene, were predisposed to infidelity.
But University of Sydney professor of medicine and molecular genetics Ron Trent said proving that a "cheating gene" existed would be difficult.
"There may be some sort of connection but these are complex traits and a lot of these situations involve a combination of genes and environmental factors," Dr Trent said.
"For one, we cannot prove infidelity runs in families," he explained.
Running an adultery website has not made Biderman insecure about his marriage but it has made him more pragmatic.
"It has challenged the paradigm I grew up with, that you should just get married. But there is more diversity than that out there," he said.
NSW Family First representative the Reverend Gordon Moyes said the popularity of such sites was disappointing, if not surprising.
"Infidelity solves nothing. It is not surprising that there are significant numbers of people who think they can get out of their rather boring malaise within their existing marriage by having an affair," Moyes said.
"However, you only have to read the celebrity pages to realise that the other partner often responds badly," he stated.
Biderman said the Australian site had higher levels of female participation than sites in the US and Britain.
"Women who use the service haven't been paid attention to, these women who were once such objects of desire that someone married them," he said.
University of Sydney behavioural scientist Dr Di Sansom said some people rediscovered the love they felt for their spouse after partaking in an affair.
"They find it is not as fulfilling as their marriage and so they end it," he revealed.
Biderman said his website was allowing more than 5.8 million people internationally to test the waters.
"It is hard for people to shed that idea of monogamy. When they are tired of vanilla, they want to try different flavours," he added.