It takes quite a long time, from my experience anyway, to recognize the subtle features in a face. Most people can differentiate between two people, but they may not be able to explain what’s different, or what makes that person stand out. I’ve trained myself to identify teeny tiny parts in a face like the length of the space between the upper lip and nose or the type of eyelid a person has. I can’t explain enough the importance of placing facial features in the right spot when drawing people. I have had drawings go from looking like weird, mutated subhumans to life-like representations because one line was shifted a few millimeters over.

This article explains a recent study into how the features of a face correlate to the amount of testosterone during a pregnancy and the ratio of length between fingers. Now, I need to point out, especially after reading the comments posted below the article, that this study does not explain the “manliness” of a male’s personality, but the look of his face. “Manliness” is described simply as having a robust face.
I’m not here to comment on the scientific accuracy of the study (although I’m not disputing its claim). I found this article fascinating because of the process of human development and the aspects of art that attract me, and so many others, to drawing and painting the human figure.