Warning! Necropost (for benefit of future readers)!

More precisely, I do not know if there is or not, but if there is not, then life has no meaning

Unless, of course, it is valid to choose your own meaning.

The fact hedonism and utilitarianism are expected consequences of natural selection greatly reduces the probability that I have neglected another, more compelling cause of hedonism or utilitarianism, namely that they are the product of keen observers of reality and keen calculators of reality's ethical implications.

Careful; easy to fall into a false dichotomy here. They can be a consequence of natural selection and a correct result for a calculation of "reality's ethical implications."

I would even go so far as to say that they are the correct ethical position because they are a result of natural selection. Or, to phrase it slightly better: because our evolution ended up this way, utilitarianism is the correct ethical approach. A species that did not evolve to experience suffering or pleasure would have quite different moral values.

We have evolved to experience suffering and happiness, which I would say are a priori bad and good, respectively; thus, this evolution has caused utilitarianism to be the correct ethical position (by creating bad and good).