I like to think Harmony factions treats the colonizing of new planets as they are and not treating It as 'only' 6000 years old.
Evolution is a fact, not a moral imperative.
Whether it's true is a clear scientific fact. Whether we should allow it to continue on its course without modification is a values choice.
Because in the end evolution doesn't care about you or your life - just if you end up reproducing. It doesn't care if you live a life of hardship and suffering if you manage to plop one out or if you have a fantastic life but don't breed. There is no reason to believe that allowing evolution to continue to act on humanity will necessarily lead to a better future - as such we might want to consider taking control of our own destiny with genetic engineering, bionic implants, nanotechnology, etc.
Of course the Harmony affinity isn't about letting evolution take its course at all, if anything that's Purity, they're trying to intervene in the process with genetic engineering.