How could digit length ratio be affected by socialization or cultural biases?
> Assuming a normal distribution, the 95% confidence interval for average length is 0.889-1.005 for males and 0.913-1.017 for females.
> In Manning's words, "There's more difference between a Pole and a Finn, than a man and a woman."
> 2D:4D is being used alongside other methods to help sex Palaeolithic hand stencils found in European and Indonesian caves.
other hormone effects, congenital adrenal hyperplasia can also be detected with blood tests, as was the case e.g. http://www.ncbi.nlm.nih.gov/pubmed/12414881
It's reported in all of the child studies discussed in TFA. Fault the article if you want but "hormones" is in the title, and the whole point of the entire line of research is that it's implausible that prenatal hormone levels could be affected by cultural biases.