Hadza hunter-gatherer men do not have more masculine digit ratios (2D:4D).
OBJECTIVE
The ratio between the length of the second and the length of the fourth digit (2D:4D) is sexually dimorphic such that males of many species possess a lower ratio than females, particularly in the right hand. Still, men and women often exhibit overlapping 2D:4D ranges and the ratio is highly variable between populations. In order to further explore populational variability, we chose to analyze 2D:4D in the Hadza, a population of hunter-gatherers living in Tanzania.


METHODS
Data were collected separately by two researchers over the course of three years (1998, 2001, 2006) from 152 adult participants (male: n = 76, female: n = 76). Independent samples t-tests were used to explore sex differences, paired samples t-tests were used to explore directional effects within each sex, and linear regression and one-way ANOVA were used to test possible age effects.


RESULTS
In none of the years, or pooled (n = 152), did we find evidence that adult men have a lower 2D:4D than adult women. If anything, the data suggest that women in this population have a significantly lower right hand 2D:4D than men (P < 0.001, d = 0.57). In contrast, left hand 2D:4D did not exhibit a sex difference (P = 0.862, d = 0.03).


CONCLUSIONS
These findings challenge the current view that lower 2D:4D in men is a uniform characteristic of our species. Cross-populational variance in 2D:4D may be related to known patterns of hormonal variation resulting from both genetic and environmental mechanisms, though this relationship merits further investigation.
Department of Psychology, University of Pennsylvania, Philadelphia, PA, 19104.
Coren L
CL
Apicella
Department of Psychology, University of Pennsylvania, Philadelphia, PA, 19104.|Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, 02138.
Victoria A
VA
Tobolsky
Division of Biological Anthropology, Department of Archaeology and Anthropology, Cambridge, CB2 3QG, UK.
Frank W
FW
Marlowe
Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, 02138.
Kathleen W
KW
Miller
D000885:Anthropology, Physical; D000886:Anthropometry; D005260:Female; D005385:Fingers / Q000033:anatomy & histology*; D006801:Humans; D008019:Life Style / Q000208:ethnology*; D008297:Male; D012737:Sex Factors; D013636:Tanzania / Q000208:ethnology
2D:4D; Hadza; digit ratios; hunter-gatherers; sexual dimorphism