Stay or stray? Study delves into sexual behaviour

February 4, 2015
Scientists said they had amassed the first evidence to back theories that people fall into two broad categories—promiscuity or faithfulness—when it comes to sex

Scientists said Wednesday they had amassed the first evidence to back theories that people fall into two broad categories—promiscuity or faithfulness—when it comes to sex.

Why humans seem to be an exception among mammals on the matter of sexual relationships has long been a puzzle.

Other mammalian species are emphatically polygamous or monogamous as a group.

But as everyone knows anecdotally, Homo sapiens do not fall into one neat category or the other.

Everyone knows of couples that are sexually faithful, but also of men cut out to be cads rather than dads.

What has been lacking are the statistics to show these differences, which is a key step to explaining them.

Now a team at the University of Oxford say they have found just that.

"We observed what appears to be a cluster of males and a cluster of females who are more inclined to 'stay,' with a separate cluster of males and females being more inclined to 'stray' when it comes to sexual relationships," said Rafael Wlodarski, an experimental psychologist and study co-author.

Wlodarski and a team looked at two potential indicators of .

One source was an online questionnaire on sexual habits, completed by 585 North American and British respondents between the ages of 18 and 63, who on average were nearly 25.

The longer your ring finger is, compared to your index finger, the higher the likely concentrations of foetal testosterone, which in turn has been linked to a higher statistical likelihood of promiscuity

Finger length

The other was data obtained from 1,314 British men and women—an investigation based on something known as the "2D:4D" ratio.

What lies behind the 2D:4D idea is that the length of one's ring finger indicates the level of the hormone testosterone to which one was exposed in the womb.

The longer your is, compared to your index finger, the higher the likely concentrations of foetal testosterone.

This in turn has been linked to a higher statistical likelihood of .

Comparing the questionnaire results to the 2D:4D study gave the investigators the data they craved, they wrote in the British journal Biology Letters.

Put together, the datasets showed that 57 percent of men were more likely to be promiscuous, and 43 percent faithful.

This balance inversed among women—47 percent fell within the "stray" category and 53 percent in "stay".

Taken alone, the 2D:4D study, based on a purely physiological characteristic, yielded higher "stray" numbers for both men and women—62 percent and 50 percent respectively.

The higher number of "stay" candidates in the questionnaire study may be explained by the influence of life experience and culture.

This very difference underlined the need for caution in interpreting their results, the researchers said.

"Human behaviour is influenced by many factors, such as the environment and ," said Robin Dunbar, a professor at the Oxford unit that did the research.

"What happens in the womb might have only have a very minor effect on something as complex as sexual relationships."

How can different sexual behaviours be explained?

Seen through a Darwinian lens, sex with multiple partners boosts the chances of offspring—of passing on one's genes.

A long-term requires more personal investment. But it increases chances that the offspring that results from the sex will survive.

"This research suggest that there may be two distinct types of individuals within each sex, pursuing different mating strategies," said the authors.

Explore further: Finger length clue to motor neuron disease

More information: Stay or Stray? Evidence for Alternative Mating Strategy Phenotypes in Both Men and Women, Biology Letters, rsbl.royalsocietypublishing.or … .1098/rsbl.2014.0977

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9 comments

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RhoidSlayer
5 / 5 (1) Feb 04, 2015
supply and demand . protect scarcity and reap abundance .
societies have tried to redistribute the wealth , condemning promiscuity and rewarding monogamy ,
but it's not really a good strategy to turn down the opposite sex if there's a line and the pay is good.
Kedas
2 / 5 (5) Feb 04, 2015
Lets just say it, some brains are more evolved than others.
Some are just still doing it like the animals do it.
RhoidSlayer
not rated yet Feb 04, 2015
delete me
Shabs42
5 / 5 (2) Feb 04, 2015
Lets just say it, some brains are more evolved than others.
Some are just still doing it like the animals do it.


Like which animals? Many animals are polygamous, many others are monogamous. Wouldn't say one is "more evolved" than the other.
Gaby_64
1 / 5 (3) Feb 04, 2015
id say that the monogamous are less evolved mentally, we are overpopulated and you have no idea what you are subjecting your progeny to, the future is insane.

on a second note, we are all stuck, conscious, living the human condition, we should definitely lighten things up by being more promiscuous. granted it needs to be done consciously and safely, consensual mutually beneficial and safe experience for all parties involved, including the environment.
Kedas
1 / 5 (1) Feb 05, 2015
Lets just say it, some brains are more evolved than others.
Some are just still doing it like the animals do it.


Like which animals? Many animals are polygamous, many others are monogamous. Wouldn't say one is "more evolved" than the other.


monogamous animals are a very small minority. (and some can probably learn from them)
Basically I see the difference as those that are just going around using the primitive part of their brain for it and those that don't.

MarvinF77
1 / 5 (1) Feb 05, 2015
I've experienced the complete opposite to what this article promotes. I shudder at the thought that this article will have more effect on its readers than intrauterine exposure to testosterone. Go cheat if your finger measures up, here's your excuse.
tj10
1 / 5 (1) Feb 09, 2015
"Scientists said Wednesday they had amassed the first evidence to back theories that people fall into two broad categories—promiscuity or faithfulness—when it comes to sex."

????

I could have told you that without doing the research! What other types could there be?!!

Why do they feel like they have to "explain" this in Darwinian terms? It might simply have to do with their faith, values, their upbringing, their environment, the opportunities, etc. So everyone who cheats plans on it? I'm sure sometimes temptation just gets the best of some people.

What does that have to do with evolution?

Is he saying that some men evolved to be cheaters and others evolved to be faithful? No personal responsibility, right? What utter foolishness!

We all evolved to be sinners and we all have to fight temptation to stay faithful. Any one of us is capable of falling into the straying category. We need to be aware of that and take precautions to remain faithful.
Royalcourtier
1 / 5 (1) Mar 26, 2015
"men cut out to be cads rather than dads". But what about women cut out to be promiscuous?

The rate amongst women is actually very close to that of men, contrary to the traditional anthropological view than men spread their seed as widely as they can, whilst women stay in the cave bringing up babies.

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