Theirs a gene family called Bcl 2 (http://en.wikipedia.org/wiki/Bcl-2_family) which controls the way human body degrades , unless someone can find out how to stop that and since its the human body itself that is killing itself , it would be extremely hard to make humans immortal .....the lifespan of humans may increase ,but if humans were to be immortal, it is only going to add towards man kind trying to end itself , which is ironical ...