This is absolutely something to potentially be worried about, but one thing I never see highlighted in critiques of AI-assisted cognition is that some elements of physiology may not actually be biologically necessary if they can be fully supplanted by some replacement (in this case, new tools). I can't traverse as much land on foot as my ancestors did (my muscles are weaker, my endurance is less, etc), but I can travel even further than they could by car/plane/etc.

Nothing about the nature of evolution implies our current cognitive processing is ideal/sacred and shouldn't ever change.