Scientists believe they have found the ‘macho’ gene which makes men behave more aggressively than women under stress. They say this one gene could explain why men have a ‘fight or flight’ response while women are more likely to try and defuse the situation, a response known as ‘tend and befriend’.
Australian researchers have studied the chemicals secreted by men when they react to stress – and how this influences their behavior.
And they propose that the SRY gene – only found on the Y chromosome – and the proteins it activates in the body, are the key.
This gene was previously thought just to be involved in the development of male characteristics in the womb.
But Dr Joohyung Lee and Professor Vincent Harley from Prince Henry’s Institute in Melbourne have shown these proteins are actually present in the brain and other organs of adult males.
They have shown these may regulate stress hormones and blood pressure which cause stressed-out men to experience their pulse quickening and adrenaline coursing through their veins – triggering aggression.
In women, psychologists believe this behaviour is countered by the release of oestrogen and the ‘cuddle hormone’ oxytocin.
Dr Lee said: ‘The aggressive fight-or-flight reaction is more dominant in men, while women predominantly adopt a less aggressive tend-and-befriend response.
‘New evidence indicates that the SRY gene exerts “maleness” by acting directly on the brain and peripheral tissues to regulate movement and blood pressure in males.
‘In view of this, we propose SRY provides a genetic basis to explain why the “fight flight” response Is manifested mainly in males rather than females.’
Although research into this has mainly been carried out in men – with no direct comparison to stress in women – they believe it could helps psychologists and lead to new treatments for personality disorders.
It could also explain why some conditions – such as Attention Deficit Hyperactivity Disorder, autism and Parkinson’s disease – affect more men than women.
Studies in rats and humans found SRY proteins in the brain, heart, lungs, liver, kidneys and testes. They believe it regulates production of catecholamines – stress hormones including adrenaline.
These cause ‘fight or flight’ – the physical reaction to a threat, experienced by all animals – in which hormones cause symptoms such a quickening-pulse, slow digestion, dilated pupils and shaking.
Females have been shown to have a different response – protecting their young or trying to reduce tension by seeking the support of others.
Co-author Professor Harley said: ‘People long thought that SRY’s only function was to form the testes. Then we found SRY protein in the human brain and with UCLA researchers led by Professor Eric Vilain, showed that the protein controls movement in males via dopamine.’
‘This suggests SRY exerts male-specific effects in tissues outside the testis, such as regulating cardiovascular function and neural activity, both of which play a vital role in our response to stress.’
The study is published tomorrow in the journal BioEssays.