Most people, sure, but we’ve had a few rather insightful people over the years write their ideas down for the rest of us to ponder on at our liesure. 
This is patently false. Evolution, as a concept, was not a factor in public or private discourse in any significant way for centuries. That you now have accepted a worldview that makes the conclusion inevitable says more about you than the universe, to this relativist.
Justifications come to an end. Simply because to justify everything I would need an infinite hierarchy of epistemologies doesn’t mean I must create them, or that they exist at all. This argument (yours) is quite similar to one in Stanford’s Encyclopedia of Philosophy’s (http://plato.stanford.edu/contents.html) demanding that relativism is self-defeating, or that relativism in one sense demands realism in another. Justifications come to an end; in naturalized epistemologies, that end might be behavior:
Naturalized epistemologies are funny things; they’re almost circular in that they presuppose the existence and possession of knowledge in seeking knowledge, but not so circular in the sense that they name specific propositions are true. Modern science is one such idea, and in fact naturalized epistemology is largely considered as simply science. Naturalized morality, a version of which you very much seem to be proposing, would then of course fall under the same methodology. more Wittgenstein:
This is almost the charge of the relativist, that eventually you will reach a point where justifications are no longer possible, and at this point we can still observe variations. Naturally speaking, we can push any person to explain their moral behavior and justify it, but eventually (we’re inside naturalism, remember) we’ll get to the point where they just act, that is simply what they do. But people do act differently, and we can’t justify all of our activity. If these activities, this isness not shouldness of behavior, is in fact the top of our hierarchy or the bedrock of our grounds, and they differ, then there is no hope for the absolute system. Point of fact, we are different.
Now I lean towards naturalistic explanations myself, but I don’t find an overwhelming urge to think there is thus an ultimate method of evaluation. My underlying assumption that the universe has a definite nature does not make the pluralities that exist go away, and it does not offer me a way to make them go away. I have to live with them. They are all around me, in the way people think microwave buttons should function to whether or not we should wage war on the other side of the globe. I think naturalized epistemologies are powerful tools, and I think they serve a practical function, but you might say that that is because I happen to value practicality in many ways, and if you ask me to justify this I will reach a point where I can no longer. I will appeal, analytically, to assumptions I have made; naturalistically, I will simply say, “This is how I am.” Logically, starting with the idea of reality as a definite thing leads us toward foundationalism, a series of propositions from which we may deduce properties, and these propositions form a system. Euclidean and non-Euclidean geometries are two examples of foundational perspectives. Naturalistically, starting with the idea of reality as a definite thing leads us to ways of life that we learned before we gained critical faculties; that is, we were taught how to reason and how to judge before we could reason and judge, or perhaps it is biological in nature, shaped by the very formation of our brains: neither case assures us of soundness absolutely, and because we may cause our own extinction many ways over through a series of rational choices (“it seemed like a good idea at the time”), the very fact that we are alive now is not an indication of [natural] moral soundness.
This is simply unfounded. If no method of permanent survival exists, there is no universal goodness at all and your argument defeats itself by defining something that doesn’t exist. While moral skepticism is something we should keep in mind in all moral arguments, reducing absolute standards to nonsense in potential cases should indicate a flaw in reasoning.
If more than one method of survival exists, then even with an objective standard plural systems are possible and relativism remains unfettered; granted, you’ve managed to create a form of relativism where there are multiple valid systems, but it is quite another to say they will all cooperate if people discover them independently, so we haven’t exactly ruled out moral dilemmas or guaranteed that their interaction won’t undermine their validity.
If one system exists, relativism remains until such time as we discover the system. Its existence can be assumed, but the argument you present is then trivial and uninteresting: I will simply assume it doesn’t and we make no headway. You want to show us flies out of the bottle, we can’t get outside just because you say only one opening exists, we have to find it. Until then, we’ll look in our own way (appeal to naturalistic grounds) or the way we think is appropriate given our assumptions (appeal foundational grounds). You may even go so far as to laugh at us and say the foundational grounds and the natural grounds are “really” the same thing, but don’t be surprised when we brush you off until such time as it is demonstrated to both our satisfactions: something, if you reflect on it, that will be pretty hard to do! 
so neither the goals, nor the means to get to them, are my design but rather the universe’s design. Gotcha. Nope, no teleology there at all… 
