I did bother reading the rest of this thread, and all you gave was further "how". How did it come to be that living things that are around today behave in ways that tend to increase the propagation of their genes? Those that didn't died out, leaving only these ones behind. That's a "how". And to be fair, "why" is an overloaded term, and one sense of it does mean "how", so you've technically answered one sense of the question, but clearly people are asking for an answer to the other sense of it, which you might put as "how come?" In other words, for what purpose?
Purposes are not causes. They don't explain why things are, and no amount of explaining why things are will tell you its purpose. A purpose is why something ought to be, what it's good for. To answer that, you first need to answer what is good, what ought to be, in the general (which no amount of discussion about what is or is not will accomplish, as it's a completely separate, orthogonal question); and then answer how the something in particular furthers that end (probably quite indirectly).
You could actually be interpreted as having given an answer to that question, if "My biological function..." is meant not to merely describe what you do do, but to prescribe what you ought to do. If you're saying "the good that my existence serves is propagating the existence of organisms like me", then that's an answer. One that implies that the existence of organisms like you is good (either intrinsically or at least instrumentally), and that your existence tends to propagate their existence (which is only the case if you're actually likely to procreate).
I'd argue that it's possibly not the best answer (if you mean that the existence, or propagation thereof, of organisms like you is an intrinsic good, rather than merely an instrumental one), and it's possibly a rather sad one (if the only thing you're good for is giving someone else a chance to try again next generation), but it could still technically be an answer, if you meant it in that sense.
Your doubling down on the "how is all the why there is", though, makes me doubt you did mean it in that sense.