It's just necessity, probably something to do with the testosterone in teenage males makes space marine development process possible. Although theoretically it would be possible to to have female space marines they would probably require hormone injections on the level of a sex change. I also highly doubt that they would have breasts, just look at some female body builders. I imagine the mortality rate for such a process would be much much higher that the already substantial risk for male applicants, to the point where it is simply unfeasible.
You're right, but you're kinda wrong, this is why female space marines cannot exist: The emperor was male All primarchs are male, All marines are derived from the same methods used to make the primarchs All space marine genetic manipulation and implants etc. were designed for use with the XY (male) chromosomes. Regardless of the amount of hormones used, you can't change the chromosomes in a women. The vast majority of men are naturally stronger and tougher than the vast majority of women, thus making better soldiers. (why would you use worse material for soldiers if you have the choice?) The imperium couldn't give a fuck about equality.
Recruits must be fairly young, because implants often do not become fully functional if the recipient has reached a certain level of physical maturity. They must be male because the zygotes are keyed to male hormones and tissue types. Only a small percentage of people are compatible to receive the implants and hypno-suggestion to turn them into Marines. Before the process of implantation begins the potential recruit receives tissue compatibility tests and psychological screening. If the testing proves successful the recruit becomes a neophyte. After the organ implantation process he becomes aninitiate.[1][2a][3] Even once the organs are implanted they are generally inactive or useless without associated training and hypnotherapy and chemical treatment. Most recruits join the ranks as a brother between the age of 16-18 years. I cant comment on equality, i think nobody sees any difference anymore. 1 point is achieved though. The rest is contested material. For example emperor is male, that is good to know i always though he was a women with that long and fabulous hair of his, all primarchs are male good eye there, but the primarchs are far bigger then space marines in height, if a human is 6 feet then a space marine is 7 feet and the primarch 8 feet which means there is a difference in how a space marine is made and a primarch, otherwise we would have thousands of primarchs, the space marines template of design is from the primarchs though, the genetic material to help them kick off the genomes, while primarchs came from the emperor him self, he messed with them on an genetic lvl, so leman russ got wolf dna, the template transfers and bam space wolf got canine dna. But guess what, this is warhammer 40k, not reality, if it says this is how to make a space marine then that is that. BUT THEN! ALL OF AN SUDDEN! GAMES WORKSHOP APPEARS! A laboratory is discovered some 11,000 years into the future since the space marine / primarch project, some tech priests found plans on how to make female space marines, they can not be fully pledged space marines because they lack the chromosome and the zygotes needed, but can still hold 14 organs which would make them strong but not as great as original space marines, so they give them a different specialty with other organ boosts which some animals have. Shazam! there we have it, everything is possible, nothing is impossible when it comes to imagination and fiction. http://warhammer40k.wikia.com/wiki/Cursed_21st_Founding It happened once with the 21st founding, on history part, it can happen again, the land raider was made through an STC template from the dark age of technology, its not a new invention. It can happen.
They're still wouldn't be true space marines though. They'd be nothing more than a heretical experiment.
Doesn't say "Female Space Marines" it says Adventurers, but I get your point. I guess they're like squats now.
People can make anything they want. I'm sure someone somewhere has made ork space marines! Fans of Warhammer/40K are creative and I have seen many DIY chapters, to include female ones. Obviously (to most) GW will never have female space marines and you will not find them in any games based on 40K.
