I think the more likely situation was that, given that humans spend so much of their energy in their brains, early humans had high selection pressure to make th

I think the more likely situation was that, given that humans spend so much of their energy in their brains, early humans had high selection pressure to make this process more efficient. We spend roughly 10% of our entire energy budget on those ion channels. Keeping neurons at -70mV takes a lot of work.