User blog comment:Legionaire22/AT Chaos Vote/@comment-1932673-20111024122250/@comment-76.217.129.118-20111026205052

That's why the symbiote would exist. For example, females can't become astartes, so they would never have a chance at being a Warmaster. The symbiote could see the potential in a woman and choose her.

Again, this is just an idea to open up more possibilities.