Ron Hoggan wrote: "But I think that the whole idea behind the healthful benefits of paleo foods is that if they were eaten long enough humans developed an adaptation to them."

However, Ron, most people who are doing Paleo seem to want a diet that promote optimal health, whereas nature doesn't care if optimal health is achieved or not, it only works to encourage the survival of those species that can reproduce and take care of the offspring. 

The giant panda is an interesting example of a species that seems incompletely adapted to the main food it eats (bamboo shoots and leaves), despite eating it for millions of years, yet it survived and thrived for millions of years despite incomplete adaptation (perhaps because the bamboo was so abundant for so long and there was little competition), so nature didn't "care" that it wasn't fully adapted.

Thus, it's quite possible that hominins could have eaten groundnuts for millions of years (which they apparently did, based on the evidence) without becoming fully adapted to them (which nearly everyone in Paleo circles seems to accept about peanuts--although eating boiled peanuts, instead of roasted or dry roasted, might produce less deleterious results). Thus, peanuts and other groundnuts may be edible "naked, with a sharp stick," but they may not be optimal and no one knows how long it takes to adapt to various foods. Do you follow me?