[Reincarnate]

The problem is that things become confusing when you start talking about problems like these in terms of vague constructs like "purpose." It's much easier to tackle these problems through a materialist/evolutionary standpoint. "Purpose" is just "an inherent inclination to seek utility and avoid disutility" at the most basic level, and you can trace that concept back clear to the ideas of abiogenesis if you like. The same concept will always apply at every step of the evolutionary pathway. I use "utility" here loosely, as it can either mean "happiness" if you're a sentient being, or "useful things for survival" if you're not -- with those concepts gradually melting into each other (and yet remaining virtually identical) at all steps in between.