These guys are not what you would call, normal humans. They were grown in "test tubes". Designed solely for superior hand to hand combat, and sheer bottom clenching terror! All of them have a genetic defect which, for the most part, is an advantage to them. Muscle mass and body growth is continual thus giving them blindingly super human strength.
This comes at a price however, if they don't die from the lack of phallas and anus (being unable to excrete or urinate) they will buckle under their own weight as a pile of muscle. Parcel have developed a way to control this, yet it requires painful surgery to undergo.
As mentioned before, they lack the phallas and anus, plus the nipples and naval. The reason being is because they were bred that way. A quick and cheap way to control soldiers. If they aren't thinking with their penis, then they are using their brain, simple as that!