Is gender biologically or socially determined?
There has been a lot of debate amongst scientist, and they are not in agreement on any one argument. In general, there is a trend towards thinking that gender identity is based on biology.

Argument that gender identity is based on biology:


http://www.sciencedaily.com/releases/2015/02/150213112317.htm
https://www.psychologicalscience.org/index.php/news/releases/transgender-kids-show-consistent-gender-identity-across-measures.html
http://www.scienceworldreport.com/articles/21032/20150109/gender-identity-determined-brain-region-cross-links.htm


The arguments here are that the brain patterns of transgendered people are more similar to the brain patterns of people of the gender that they identify with, which seems to indicate that gender identity is based in biology.

Argument that there is a lot more to be understood:


http://steinhardt.nyu.edu/opus/issues/2011/spring/gender_identity_development



  "Neither the affects of prenatal and puberty hormones nor socialization alone are enough to explain gender identity development, the process must lie in a brain structure."