: Which is basically what the Forerunners do, go from something stated to be
: very similar to what a human looks like physically to many aesthetically
: different looking forms dependent on their rate through mutations(i think
: that's what it was called, to lazy to look it up), and depending on
: whether being 1st, 2nd, 3rd(was there any Forerunner stated as being a 4th
: form?) ,or ?4th? form, would look slightly different within the same rate.

: Just looking at what humans have done with crops makes it plausible that one
: day we could guide our own evolution and improvement. Isn't it largely
: accepted that humans are already a huge abnormality in evolutionary terms
: because of our development of higher thought processes and a comparatively
: weak physical form in the animal kingdom.

And this is where the definition of 'evolution' gets all messed up.
1) Adjustments to the genome typically involve moving, or removing genetic markers that allow for abilities already existing in the genome but previously suppressed or locked. This is basically the same result of mutation.
2) If anyone were to be able to somehow insert another kind of animal's genes to provide some ability that did not exist before (eg what punctuated equilibrium implies), all that shows is that intelligence was required to make it happen - but evolution by definition has to occur by chance, through entirely natural processes, without some 'higher' guidance.

And this is why the Librarian's use of 'evolution' in the actions she took are confusing at best. If she 'guided' evolution, then the Chief's new abilities were already there (in humanity) and she just unlocked them early (the implication in the fiction being that they would indeed have unlocked naturally in the future), or she gave the ability to him in which case she's like a "god" playing with the genome rather than this being the result of naturalistic evolution.
I believe the former is the more accepted explanation :) So whatever happened, humanity was implanted with the genetic code that would eventually in time be unlocked through natural evolution; she just sped that up for the chief himself.