It's clearly a scientific issue, but also a social issue. There is a scientific definition of what a woman is, and there is a social definition (which is very close to the scientific definition, but which does depend a bit on culture and which can change over time). A lot of the debate comes from people talking past one another, without acknowledging that they're using the same word to discuss different topics.

One of wikipedias biggest issues is its inability to cope with words that have different but overlapping meanings.