I am always a student with a double major in biological sciences and have worked in a genetics lab... for several years. Genetics does play a role. You cannot *spin* that away.
If you have yourself convinced that genetics does not play a role, you perhaps need to unlearn a whole bunch of false ideas\thoughts... if you care to face reality. I know that most people refuse to face *some* realities... even though they may be *enlightened* in other things.
About lifespan...
Environment and the harshness of it, plays a huge role in lifespan... go ahead... live life where you are without any electricity, gas, and running water.