Self preservation

These monkeys surprised scientists by sharing even more when no one was looking

These monkeys don't like other monkeys seeing you give food away. I would guess it is because the other monkeys will want it.

I am a dualist, we both  propagate the  species and build walls against personal threat.  The authors in this great study focus on genetic propagation.  However, there is evolution inside us among the mitochondria, the winner of that battle is the mitochondria that best preserves the host, not really propagate the host. We are a dual system, an ecosystem. Self preservation and sex are mostly in conflict.