̽��ֱ�� of Cambridge - Danny Longman

‘Believing you’re a winner’ gives men a testosterone boost and promiscuous disposition

fpjl2 — Thu, 09 Aug 2018 08:36:05 +0000

A new study shows that men only have to believe they’ve bested another man in competition to get raised testosterone levels and an inflated sense of their own value as a sexual prospect.

Scientists found that this hormonal and psychological shift made men more inclined to approach new potential partners.

̽��ֱ��research team measured hormone levels, as well as self-perceived attractiveness and confidence in approaching women, in 38 men in their twenties before and after competing in head-to-head battles on rowing machines.

Unbeknownst to participants, the competitions in the study were rigged to randomly declare the winner, regardless of who was the stronger rower.

While previous studies have shown that winning can affect male hormones, it was not known whether this was down to the efforts it takes to win or the belief that one is victorious.

̽��ֱ��latest study, led by biological anthropologists from the ̽��ֱ�� of Cambridge and published today in the journal Human Nature, reveals that just being convinced you have won, or indeed lost, is enough to cause male hormonal fluctuations that can influence sexual behaviour.

Researchers say this is an example of “plasticity”: the body adapting quickly – without altering genetic make-up – to suit a change in circumstance. In this case a perceived change in social status, due to the men believing they have defeated a rival.

̽��ֱ��body attempts to take advantage of this apparent status improvement by inducing chemical and consequently behavioural changes that promote a “short-term” approach to reproductive success, say the researchers. Namely, more sex with new and different partners.

“Much of evolution consists of trade-offs in energy investment,” said study lead author Dr Danny Longman, from Cambridge’s Department of Archaeology.

“A common trade-off for males both across and within species is between mating strategies. One reproductive approach is short-term, investing time and energy in attracting and pursuing many mates, and fighting off competition. Another approach is long-term, investing energy in raising offspring with a single mate.”

“We found that a perceived shift in social status can cause male physiology to adapt by preparing to shift mating strategies to optimise reproductive success.”

Longman points out that in many animal populations, male social hierarchies correspond with reproductive success, and social status is determined by competition between males.

̽��ֱ��study used a simple proxy for social and sexual competition by pitting athletic young men against each other to see who was the most powerful rower.

“Victory in a rowing contest strongly implies the possession of greater physical strength than the opponent, a trait found to be valued by women in our evolutionary past when choosing a mate,” said Longman.

He took saliva samples to test hormone levels before and after the races. A number of psychological questionnaires were also administered, designed to gauge self-esteem, ‘sociosexuality’ (willingness to engage in casual sex), ‘self-perceived mate value’ and mating behaviour (e.g. the likelihood of approaching attractive women). Crucially, Longman and colleagues then manipulated the results of the races.

̽��ֱ��men who believed they had won received an average testosterone increase of 4.92%, while those convinced they had lost dropped by an average of 7.24%. Overall, men who thought they were winners had testosterone levels 14.46% higher their deflated opponents.

̽��ֱ��men who thought they had lost showed no difference in their perceived value as a mate or confidence approaching women. However, the men who felt like winners had a ‘self-perceived mate value’ that was 6.53% higher, on average, than their rivals, and were 11.29% more likely to approach attractive women in an effort to instigate sexual relations.

“ ̽��ֱ��endocrine system that controls hormones is responsive to situational changes. Previous research has shown that testosterone is lower when men are in a committed relationship, or have children, to promote long-term mating strategies,” said Longman.

“Our results show that both testosterone and its corresponding psychological effects can fluctuate quickly and opportunistically, shifting towards short-term mating in response to a perceived change in status that may increase mating value.”

Male social status has less to do with physical strength in many modern societies, and Longman would be curious to see if similar results arise from intellectual challenges more familiar to the office-based culture many men now inhabit. There is always the issue of free will, however.

“Male physiology may shift to take advantage of certain situations, but ultimately a man’s decisions are up to him.”

New findings suggest that the male body tries to “optimise” self-perceived improvements in social status through hormonal shifts that promote “short-term mating”.

Our results show that both testosterone and its corresponding psychological effects can fluctuate quickly and opportunistically

Danny Longman

U.S. Army

U.S. Army World Class Athlete Program wrestler Spc. Jeremiah Davis (right) squares off against Sunkist Kids' Joe Betterman

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'Selfish brain' wins out when competing with muscle power, study finds

fpjl2 — Fri, 20 Oct 2017 11:51:43 +0000

Human brains are expensive – metabolically speaking. It takes lot of energy to run our sophisticated grey matter, and that comes at an evolutionary cost.

Now, a new investigation into the immediate trade-off that occurs inside us when we have to think fast and work hard at the same time is the first to demonstrate that – while both are impaired – our mental ability is less affected than our physical capacity.

Researchers say that the findings suggest a "preferential allocation of glucose to the brain", which they argue is likely to be an evolved trait – as prioritising quick thinking over fast moving, for example, may have helped our species survive and thrive.

Scientists from the ̽��ֱ�� of Cambridge's PAVE (Phenotypic Adaptability, Variation and Evolution) research group tested 62 male students drawn from the ̽��ֱ��'s elite rowing crews. ̽��ֱ��participants had an average age of 21.

̽��ֱ��rowers performed two separate tasks: one memory, a three minute word recall test, and one physical, a three minute power test on a rowing machine.

They then performed both tasks at once, with individual scores compared to those from previous tests. As expected, the challenge of rowing and remembering at the same time reduced both physical and mental performance.

However, the research team found that change in recall was significantly less than the change in power output.

During the simultaneous challenge, recall fell by an average of 9.7%, while power fell by an average of 12.6%. Across all participants the drop in physical power was on average 29.8% greater than drop in cognitive function.

̽��ֱ��team say the results of their new study, published today in the journal Scientific Reports, add evidence to the 'selfish brain' hypothesis: that the brain has evolved to prioritise its own energy needs over those of peripheral organs, such as skeletal muscle.

"A well-fuelled brain may have offered us better survival odds than well-fuelled muscles when facing an environmental challenge," said Dr Danny Longman, the study's lead author from the PAVE team in Cambridge's Department of Archaeology.

" ̽��ֱ��development of an enlarged and elaborated brain is considered a defining characteristic of human evolution, but one that has come as a result of trade-offs.

"At the evolutionary level, our brains have arguably cost us decreased investment in muscle as well as a shrunken digestive system.

"Developmentally, human babies have more stored fat than other mammals, acting as an energy buffer that feeds our high cerebral requirements.

"On an acute level, we have now demonstrated that when humans simultaneously experience extremes of physical and mental exertion, our internal trade-off preserves cognitive function as the body's priority."

̽��ֱ��adult brain derives its energy almost exclusively from the metabolism of glucose. Yet skeletal muscle mass is also energetically expensive tissue, accounting for 20% of the human male 'basal metabolic rate' – the energy used when doing nothing.

Longman says a limited supply of blood glucose and oxygen means that, when active, skeletal muscle becomes a "powerful competitor" to the brain. "This is the potential mechanism for the fast-acting trade-off in brain and muscle function we see in just a three minute window."

"Trade-offs between organs and tissues allow many organisms to endure conditions of energy deficit through internal prioritising. However, this comes at a cost," said Longman.

He points to examples of this trade-off benefiting the brain in humans. " ̽��ֱ��selfish nature of the brain has been observed in the unique preservation of brain mass as bodies waste away in people suffering from long-term malnutrition or starvation, as well as in children born with growth restriction."

New research on our internal trade-off when physical and mental performance are put in direct competition has found that cognition takes less of a hit, suggesting more energy is diverted to the brain than body muscle. Researchers say the findings support the ‘selfish brain’ theory of human evolution.

A well-fuelled brain may have offered us better survival odds than well-fuelled muscles when facing an environmental challenge

Danny Longman

Lead researcher Dr Danny Longman rowing with the Cambridge ̽��ֱ�� Boat Club. This is an example of the type and standard of the sample population used in the study.

̽��ֱ��study

Protocol A – isolated power test:
Participants rowed at maximal effort for 3 minutes, and their average Wattage was recorded.

Protocol B – isolated recall test:
Participants performed a free recall word task in which they were shown 75 words from the Toronto Word Pool for a 3 minute period. They then had 5 minutes to recall and write as many words as possible. ̽��ֱ��number of words correctly recalled during a given time period was recorded.

Protocol C – combined 'trade-off' test:
Participants did both (but with a different word set), and their average Wattage and number of words correctly recalled was recorded. Researchers used 'paired samples t-tests' to compare power output between Protocols A and C, and for comparing free recall in Protocols B and C. They then compared the two differences, and found that the percentage change in free recall was significantly less than the percentage change in power output – an average of 29.8%.

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Distance running may be an evolutionary ‘signal’ for desirable male genes

fpjl2 — Wed, 08 Apr 2015 18:05:25 +0000

Pre-birth exposure to high levels of the male sex hormone testosterone has already been shown to confer evolutionary advantages for men: strength of sex drive, sperm count, cardiovascular efficiency and spatial awareness, for example.

Now, latest research on marathon runners using finger length as a marker for hormone exposure shows that people who experienced higher testosterone in the womb are also better at distance running – a correlation particularly strong in men, although also present in women.

Researchers say the finding that males with greater “reproductive potential” from an evolutionary standpoint are better distance runners suggests females may have selected for such athletic endurance when mating during our hunter-gatherer past, perhaps because ‘persistence hunting’ – exhausting prey by tirelessly tracking it – was a vital way to get food.

Distance running may also have acted as a positive ‘signal’ for females of desirable male genetics more generally, say researchers: good runners were likely to be better persistence hunters and consequently better providers. This increases the likelihood they would have other key traits of good providers such as intelligence and generosity.

̽��ֱ��study was conducted by researchers at the ̽��ֱ�� of Cambridge’s Division of Biological Anthropology and is published today in the journal PLOS ONE.

“ ̽��ֱ��observation that endurance running ability is connected to reproductive potential in men suggests that women in our hunter-gatherer past were able to observe running as a signal for a good breeding partner,” said the study’s lead author Dr Danny Longman.

“It was thought that a better hunter would have got more meat, and had a healthier – and larger – family as a consequence of providing more meat for his family. But hunter-gatherers may have used egalitarian systems with equal meat distribution as we see in remaining tribes today. In which case more meat is not a factor, but the ability to get meat would signal underlying traits of athletic endurance, as well as intelligence – to track and outwit prey – and generosity – to contribute to tribal society. All traits you want passed on to your children,” he said.

Using the largest sample of marathon runners of any study of its kind, Longman and colleagues tested for specific finger lengths known as the 2D:4D digit ratio. Previous studies have showed that those exposed to more prenatal testosterone have a longer ring finger (4th digit) in comparison to their index finger (2nd digit).

This digit ratio is the most accurate known way to tell if an adult was exposed to higher levels of testosterone as a foetus – a proven predictor of the “potential for reproductive success” in men, say researchers.

̽��ֱ��team analysed 542 runners (439 men; 103 women) at the Robin Hood half marathon in Nottingham by photocopying hands and taking run times and other key details just after runners crossed the line.

They found that the 10% of men with the most masculine digit ratios were, on average, 24 minutes and 33 seconds faster than the 10% of men with the least masculine digit ratios.

̽��ֱ��correlation was also found in women, but was much more pronounced in men, suggesting a stronger evolutionary selection in men for running ability. ̽��ֱ��10% of women with the most masculine digit ratios were, on average, 11 minutes and 59 seconds faster than the 10% with the least masculine.

Longman points out that prenatal testosterone exposure is a very small influence on running ability that doesn’t compete with training and muscle strength when it comes to performance, but their unprecedentedly large sample size of over 500 people enabled the team to gather conclusive evidence.

“Humans are hopeless sprinters. Rabbits, for example, are much faster sprinters, despite being fat and round. But humans are fantastically efficient long-distance runners, comparable to wolves and wild coyotes,” said Longman.

“We sweat when most animals would overheat; our tendons and posture are designed to propel our next strides – there was likely a selective pressure for all these benefits during our evolution.”

Persistence hunting is thought to have been one of the earliest forms of human hunting, evolving approximately two million years ago, said Longman.

“You can still see examples of persistence hunting in parts of Africa and Mexico today. Hunters will deliberately choose the hottest time of day to hunt, and chase and track an antelope or gnu over 30 to 40 kilometres for four or five hours. ̽��ֱ��animal recovers less and less from its running until it collapses exhausted and is easy to kill,” Longman said.

“This may sound crazy, but when a hunter is relatively fit the amount of energy they expend is actually tiny compared to the energy benefits of an antelope-sized animal, for example. Before the domestication of dogs, persistence hunting may have been one of the most efficient forms of hunting, and as a consequence may have shaped human evolution.”

New research shows that males with higher ‘reproductive potential’ are better distance runners. This may have been used by females as a reliable signal of high male genetic quality during our hunter-gatherer past, as good runners are more likely to have other traits of good hunters and providers, such as intelligence and generosity.

Persistence hunting may have been one of the most efficient forms of hunting, and as a consequence may have shaped human evolution

Danny Longman

Warein

Running

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