This is pretty close to the plot of "Old mans war". After a certain age you can volenteer to join the armed forces.

Shorry about that. it`s the chilli. Gives me an endorphin rush

You might want to check out the book "The greatest show on earth" by Richard Dawkins. It`s a short summary of all the evidence for evolution.

For anyone not wearing augmented reality goggles.

I tend to use a cat/magma combo. Nothing slows down a siege better than cats. Nothing slows anything down more than cats. If only carp could be tamed.

Also "Newton`s wake" by Ken MacLeod. A funny and thought provoking novel about those left behind after the hard rapture. Meet the combat archeologists. When you are investigating tech abandoned in the first few seconds of singularity best to carry a plasma rifle.