Perspectives on Evolution

[FatAndFaithless]

I'm not sure exactly what you mean by 'humans cannot evolve'.  We are evolving.  Every organism is, all the time.  It might be hard to comprehend because our human timescales are less than a blink compared to the scales on which evolution works, but changes in allele frequency over time is absolutely happening in humans - and with enough time these changes in allele frequency leads to speciation.

I think there may be some confusion from the OP's perspective about what biological unit is evolving. The individual isn't. So no singular human is evolving, but the population of humans is evolving generation after generation.

Right.  It's not like a fish gave birth to a squirrel at some point... though I do always find Mr. Garrison's take on evolution funny.