Population Differences in Finger-Length Ratios: Ethnicity or Latitude?

@article{Loehlin2006PopulationDI,
  title={Population Differences in Finger-Length Ratios: Ethnicity or Latitude?},
  author={John C. Loehlin and Dennis McFadden and Sarah E. Medland and Nicholas G. Martin},
  journal={Archives of Sexual Behavior},
  year={2006},
  volume={35},
  pages={739-742}
}
The relative length of the second and fourth fingers (the 2D:4D ratio) has been taken to be an indicator of prenatal exposure to testosterone, and hence possibly relevant to sexual orientation and other sex-differentiated behaviors. Studies have reported a difference in this ratio between Caucasian males in Britain and in the U.S.: higher average 2D:4D ratios were obtained in Britain. This raises the question of whether differences among different Caucasian gene pools were responsible or… 
Relative Finger Lengths, Sex Differences, and Psychological Traits
TLDR
A new measure of relative finger length was investigated and shown to be superior to the traditional 2D:4D for discriminating between the sexes, and had the advantage of permitting a more analytic approach.
Sex, population origin, age and average digit length as predictors of digit ratio in three large world populations
TLDR
It is concluded that sex differences in 2D:4D are not an artifact of allometry, and sexual dimorphism remained stable throughout the ontogeny.
There is No Sex-, Handedness-, and Hand Grip Strengthrelated Dimorphism in Digit Ratio in both Sedentary and Athletic African Young People
TLDR
Sexual dimorphism and handedness related differences in digit ratio are not universal in humans and Athletes had no significantly lower digit ratio than sedentary subjects and there was no significant correlation between digit ratios.
The Relationship of Digit Ratio (2D:4D) and Gender-Role Orientation in Four National Samples
Abstract. The ratio of second to fourth finger length (2D:4D ratio) is sexually dimorphic with women having higher 2D:4D ratio than men. Recent studies on the relationship between 2D:4D ratio and
Selective Breeding for a Behavioral Trait Changes Digit Ratio
TLDR
The present results are difficult to reconcile with the notion that 2D∶4D is an effective proxy for prenatal androgen exposure; instead, it may more accurately reflect effects of glucocorticoids, or other factors that regulate any of many genes.
Brief communication: Familial resemblance in digit ratio (2D:4D).
TLDR
Familial resemblance in the second-to-fourth digit ratio (2D:4D), a proxy for prenatal androgen action, was studied in 1,260 individuals from 235 Austrian families and heritability estimates based on parent-child and full-sib dyad similarity indicated substantial genetic contributions to trait expression.
Height and 2D:4D Within and Between Ethnic Groups: Reply to Hurd and van Anders (2007)
We found the discussion of latitude and digit ratios by Hurd and van Anders (2007) most interesting, and their finding of a strong negative correlation between average heights and digit ratios across
Sexual dimorphism in the human hand proportion : A radiographic study
The proportion of the human hand, i.e., the length relationships between the fingers and palm, is known to differ between males and females. However, sexual dimorphism in the proportions of
Relationship between Ratio of Second and Fourth Digit and Obesity Traits among Different Ethnic Groups in Ilorin, North Central Nigeria
TLDR
The results imply that 2D:4D might be a good surrogate indicator for obesity, but not ethnicity, and that there was no ethnic specificity in 2D-4D ratio among study’ participants.
...
...

References

SHOWING 1-10 OF 14 REFERENCES
Sex hormones and finger length What does 2 D : 4 D indicate ?
Much recent research has focused on the ratio of the lengths of the second to fourth manual digits (2D:4D) as a predictor of the degree of expression of sexually dimorphic and other
A Reanalysis of Five Studies on Sexual Orientation and the Relative Length of the 2nd and 4th Fingers (the 2D:4D Ratio)
TLDR
It was the 2D:4D values for the heterosexual participants that varied most, particularly between the USA and the British studies, and these were responsible for many of the discrepancies in the conclusions across studies.
In-utero androgen exposure and 2nd to 4th digit length ratio-comparisons between healthy controls and females with classical congenital adrenal hyperplasia.
TLDR
2D:4D ratios determined directly from radiographs of the left hand confirm significant differences between males and females, however, female patients with virilizing CAH do not have a male digit ratio pattern suggesting that in theleft hand digit ratio development is not influenced by in-utero exposure to androgens.
2nd to 4th digit ratios, fetal testosterone and estradiol.
Masculinized Finger Length Patterns in Human Males and Females with Congenital Adrenal Hyperplasia
TLDR
Results are consistent with the idea that prenatal androgen exposure reduces the 2D:4D and plays a role in the establishment of the sex difference in human finger length patterns, and finger lengths may offer a retrospective marker of perinatal androgens exposure in humans.
Brisbane Adolescent Twin Study: Outline of study methods and research projects
An ongoing program at the Queensland Institute of Medical Research (QIMR) uses a resource of adolescent twins (2720 individuals) and their singleton siblings (1179), constituting 1324 families. A
Digit Ratio: A Pointer to Fertility, Behavior, and Health
Sex and Population Differences * Associations with Testosterone and Estrogen * Assertiveness, Aggression, Attractiveness, and the Wearing of Rings * Reproductive Success and Sexually Antagonistic
Circadian Clocks in Daily and Seasonal Control of Development
TLDR
A common thread linking plants and animals is the use of the circadian clock to sense changes in day length and to mediate a diverse number of photoperiodic responses.
...
...