London: A new study has revealed that the hormone which affects finger length is key to social behaviour.
Researchers from Liverpool University and University
of Oxford have carried out the study into the finger length
of primate species and found that cooperative behaviour is
linked to exposure to hormone levels in the womb.
The hormones, called androgens, are important in the
development of masculine characteristics such as aggression
and strength. It is also thought that prenatal androgens
affect finger length during development in the womb.
High levels of androgens, such as testosterone,
increase the length of the fourth finger in comparison to the
In their study, the researchers used finger ratios
as an indicator of the levels of exposure to the hormone and
compared this data with social behaviour in primate groups --
they found that baboons have longer fourth finger as compared
to the second finger, which suggests they have been exposed to
high levels of prenatal androgens.
These species tend to be highly competitive
and promiscuous, which suggests that exposure to a lot of
androgens before birth could be linked to the expression of
Other species, such as gibbons and many New World
species, have digit ratios that suggest low levels of prenatal
androgen exposure. These species were monogamous and less
competitive than Old World monkeys.
Emma Nelson of University of Liverpool said: "It is
thought that prenatal androgens affect the genes responsible
for the development of fingers, toes and the reproductive
"High androgen levels from a foetus or mother during
pregnancy, may alter gene function and lead to subtle changes
in relative digit length and the functioning of the
"Finger ratios do not change very much after birth and
appear to tell us something about how very early androgens
affect adult behaviour, particularly behaviour linked to
mating and reproduction."
The findings have been published in the `American
Journal of Physical Anthropology`.