

Y


Well that's a bit complicated and still shrouded in some mystery, but I'll try my best to explain it based on the writtings of a biologist called Steve Jones.
After recombination of the genes at conception, all human embryos will will develope along an identical path until around 6 weeks when an area, usually know as the "sex determining region of the Y chromosome" kicks in and triggers a change in the embryos development which results in the various internal and external organs, arranging themselves in a way that will make them develope as males.
If that Y trigger does not happen, then the embryo will simply continue along the path of developing as a female.
In other words, the biological default setting for each and every one of us is Female.
That is Why Y so important.
Hope this helps