The problem of perceived directionality(upward) was well discussed in Stephen J Gould's discussion of contingency theory in the book' A Wonderful Life' and many of his essays. Evolution to many is 'differential reproductive success' in 'adaptation to local environments'.
A counter example is parasites... whom many consider as primitive or degenerative but are for the most part highly evolved.
As pertaining to conciousnes, that is what some call 'cultural evolution' as opposed to physical or genetic evolution(though some consider both under the same general umbrella).
As pertains to the original question, I don't think that keeping a relative few genetic defectives in our society due to increased medical science will have much of an effect to wherever it is we are 'going'.
A wonderful whimsical view on our possible evolution is the subject of the Vonnegut book 'Galapagos'. Highly recommended.
Arkansas Banana Boy
Frank White lives....oh right he doesnt
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