Debatable, since evolution is directionless, whether you talk about species, societies, etc. It is just adaptation — becoming what fits the current external conditions. Infernals seem more teleological — directed toward a goal, though they might not see that goal at present.
I think it's okay to bring scientific concepts into Exalted, as long as you view them symbolically and mythically. Exalted uses mythic themes, but there's no need to restrict that to the themes of the ancient world. The mythic framework of Solars is, in many ways, centered on the past: the Golden Age that was lost but may return; the perfection that was sullied; etc. I like my Lunars directed towad the future: the possibility not yet realized; the new idea that still needs a little work; the courage to accept change, without knowing where it will lead.
Even without a wholesale reinvention of Lunar concepts, though, I think the discussion has suggested some good directions for developing the Lunar Charmset, and distinguishing it from other Exalted. Frex, Solar Charms often are all about power: big damage, perfect attacks and defenses, etc. Lunars, though, have some interesting Charms that are all about denying an enemy's advantage, such as Burrowing Devil Strike (that super-duper Artifact armor you counted on to protect you? Sorry, not against this guy) or Wound-Mastering Body Evolution (Sorry, you'll have to use your not-so-invincible, second-bes weapon now). This Charm theme of denying or evading a foe's advantages connects well with StephenLS' idea of Lunars being what you are not: In combat, they are the threat you didn't prepare for.