Why do humans “default” to female in fetal development?

Question

Is there any inherent reason why the body becomes female unless “told” by the Y-chromosome to be male as opposed to the other way around?

In: Biology

Answer 1

My first attempt at this was auto-modded for some reason, so, I’ll try again.

It’s a lower-energy-requirement situation.

Mother Nature is lazy. If you need to make both P and V shapes, it’s simply less steps to start out with the V-ish state and turn ~50% of those shapes into P shapes, than to start out with a P shape, and turn 50% of those into Vs.