Reversible switches between male–male and male–female mating behaviour by male damselflies

For many animal groups, both sexes have been reported to attempt to mate with members of their own sex. Such behaviour challenges theories of sexual selection, which predict optimization of reproductive success. We tested male mate choice between opposite- and same-sex members in the damselfly Ischnura elegans. Binary choice experiments were conducted following exposure periods in insectaries with only males or with both sexes present. We show that switches in choice between the opposite sex and the same sex can be induced and reversed again by changing the social context. We argue that the observed reversibility in male–male- and male–female-directed mating behaviour is maladaptive and a consequence of strong selection on a male's ability to alter choice between different female colour morphs.


Note from Reclaiming Natural Manhood site: Interesting research, but still has several loopholes resulting in imperfect and misleading results.

Marriage reduces dementia risk

The Times of India
New Delhi
Saturday, Augurst 02


Being single in middle age might increase risk of dementia. But being married halves the chance of developing Alzheimer's disease, says a study. A team at Karolinska Institute in Sweden has carried out the study and found the imporance of clse comapanionship in midlife -- and in fact, those who stay alone after divorce have a threefold risk of suffering Alzheigmer's in later life. According to researchers, the study has highlighted a higher risk of developing memory and cognitive problems for all those who live alone, whether single, divorced or widowed -- the reason to a great extent being social isolation.

Men just tuned to lust: Study

20 Jul 2008, 2359 hrs IST,PTI

TOI

LONDON: Men are tuned to lust, irrespective of whether they found the women next to them attractive or not, a study has suggested.
Men have for long been seen as judging women on looks alone, but a study has now shown that the increase in male sex hormone level was not influenced by the perceived attractiveness of the women.

Human testosterone triggers an automatic reaction which has evolved in man when faced with a woman, to look for mating opportunities, and it does not matter if the woman is not attractive, the research reveals.

The research, published in the journal Hormones and Behaviour , suggested that the levels of their testosterone surged to the same extent whether they were talking to an attractive woman or someone they may not fancy at all.

The research involving 63 male students aged 21 to 25 found that their testosterone levels increased by an average of around 8% after just 5 minutes exposure to a stranger from the opposite sex and in some cases to women they not find particularly attractive.

"We found a testosterone increase after only five minutes of exposure to a woman. Our results suggest that the increase in testosterone levels that we found, may be an automatic male response that activates receptors in organs and the nervous system to prepare the human body for mate attraction," said Leander van der Meij, who led the study at the University of Groningen in Holland.

He said with the increase in testosterone levels males tend to display more dominant behaviour.

"They talk more with their hands, there is more eye contact, their posture is more upright, and they are more likely to tell stories designed to impress the woman. We know that women can be attracted by these kinds of things. All this, we believe, may be fuelled by the rise in testosterone that we have found," said der Meij.

Aggressive males showed greater rise in testosterone levels, an idea supported by research that men who exhibit more dominant-like behaviour tend to make more frequent successful contact with females.