I would like to take exception to the statement that "while it may all be futile, we have to keep on living our lives. What else is there to do?".
I feel that this thread has proven that every life has significance to someone, and just resigning as the above implies ignores this 'someone'.

I simply think that, if two species of 'living' were created, the only difference being that one had an instinct (genetically or otherwise) to live, and the other not, the other one would quickly become extinct, leaving the first one to, millions of years later, wonder where this instinct came from.

In short, it 'came from' the same place/thing that shaped the rest of the human race. Evolution. Of what? Quantum oscillations.