[Sorontar]

Notch has written on why Steve is a guy (or not) and why he never designed a female body for Minecraft.

Gender in Minecraft : The Word of Notch

And from Twitter (https://twitter.com/notch/status/229140426513330176)

Yes, there's some level of retconning there, but not much. Ever since the first animal was added, the game was supposed to be genderless.
Players are of course free to project their own ideas about gender at characters. The game is just meant to not decide for you.

Sorontar