Yes, and that's exactly what makes the hypothesis so unlikely, all this immense adaptation for something that seems to come more-or-less for free with a standard mammalian body plan. The timescales we're talking about for such invasive changes would be far longer than available for the whole of the aquatic ape hypothesis, but is recent enough that there should be plenty of fossil evidence. I just don't buy it, but if ever someone digs up fossil proof I'll be happy to eat a hat or two. It is roughly in line for me with 'Hollow Earth' and 'Water as a fuel'. It smacks of backwards reasoning and wishful thinking.

But: it's harmless and whoever wants to believe in it is obviously welcome to do so.