The study was carried out by researchers from the University of
Cambridge and the Institute of Child Health, London. There was no
Where did the story come from?
The study was published in the peer-reviewed medical journal PLOS ONE. This is an open-access journal, so the study is free to read online.
Reporting of this study by the UK media was almost universally poor, with many sources making claims that were not supported by the study:
- Mail Online: "Those who run endurance races get more dates and have a higher sex drive" – unproven
- Metro: "Marathon runners are the best in bed" – unproven
- The Daily Telegraph: "Good runners are likely to have had ancestors who were excellent hunters… creating a biological advantage for their descendants and passing on the best genes" – unproven
None of the media coverage made it clear that the study was using running ability as a proxy for hunting prowess in pre-agricultural societies and had little or nothing to do with modern relationships.
This was an observational study that
aimed to test the researchers' theory that physical prowess at
endurance running is associated with male reproductive fitness. In this
study, the researchers used the digit ratio to predict reproductive
success. This is the ratio between index and ring finger, which is a
marker of hormone exposure in the womb.
What kind of research was this?
The researchers explain that the high value placed by females on male ability to acquire resources has been well documented, especially in pre-industrial societies. Before agriculture developed, hunting ability may have provided an important way of demonstrating male resourcefulness and seems to be linked to fertility, offspring survivorship and number of mates.
There are several theories that try to explain this link; one is that hunting success is a reliable signal for underlying traits such as athleticism, intelligence or generosity in distributing meat.
In “Persistence Hunting” – one of the earliest forms of human hunting – prey often required running for long distances. This may act as a reliable signal of reproductive potential, say the researchers.
Since increased testosterone exposure in the womb is associated with reproductive success, an association between testosterone and endurance running would make running prowess a reliable signal of male reproductive potential, they argue.
The researchers recruited to their study 439 men and 103 women taking
part in the Robin Hood half marathon in Nottingham in 2013.
Participants ranged between the ages of 19 and 35, and were all white
(Caucasian). The half marathon, they say, was chosen for its
appropriateness to pre-agricultural, hunter-associated running and
reflects endurance running ability.
What did the research involve?
All competitors wore small electronic chips to guarantee accurate race timings.
Photocopies were taken of the athlete’s left and right hands on finishing the race and these were used at a later date to measure the 2D:4D ratios.
The digit ratios were measured using special electronic callipers and were taken twice from each photocopy, to ensure accuracy.
The researchers then analysed the results, looking for an association between the digit ratio and the race time in each sex.
They found that among the men there was a "significant positive
correlation" between right and left hand 2D:4D ratio and marathon time,
with higher levels of performance associated with a lower, more
"masculine", digit ratio. The correlation strengthened after controlling
for age. The same was true of the female sample, but to a lesser
What were the basic results?
The researchers say their results support the theory that endurance
running ability may signal reproductive potential in men through its
association with prenatal exposure to testosterone. Running prowess they
suggest, could act as a reliable signal for male reproductive
How did the researchers interpret the results?
This study of distance runners and their digit ratios, and the
possible relationship between successful hunting and male reproductive
potential, is a little tenuous.
This was an observational study using long-distance runners as a proxy for hunters and digit ratio as a proxy for reproductive potential. The most it can show is an association between the two.
It should also be noted that:
- the study did not assess any non-runners
- the runners' ability was measured in only one race
- many qualities contribute to marathon running success, including muscle strength and mental endurance
- the study only included Caucasians, so the results may not apply to people of other ethnicities
Ways to increase your fertility levels include stopping smoking, drinking alcohol in moderation and maintaining a healthy weight through healthy eating and exercise.