Wording seems off. Because if a biped can do something, it means the body can do it. The body alters to the enviroment and conditions you give it. If your body was incapable of doing something, no amount of training would change that. Like dogs cant look up. (thats a joke before anyone gets too annoyed.) The above is closer to, "we didnt know we could train ourselves to do it" not "our body is incapable of doing it". And anything humans cant do illudes me at the moment, not breathing under water and such like that doesnt seem very releivent or apt. Maybe 360 degree head turning. Actually you know you have far too much time on your hands if you are able to devolope a high technical skill for mortal combat anyway.