I only use "paleo" as a guide when I have no information about the item's nutrition or how it interacts with a human system on a biochemical level. It's pretty rare to have a black box food these days, so the paleo invocation is kind of rare.
I don't by any means think that all of what our ancestors ate or did is ideal. My main focus is not to become a caveman, or a hypercivilized cyborg, but rather to take that which is optimal from the paleolithic and that which is optimal from the neolithic and create a synergy that is ideal for health.
If contemporary HGs are any indication, our ancestors likely took great pains to acquire honey and would consume as much of it as possible. That's fine, but I'm not convinced that a massive dose of fructose is ideal. (Though it must be said that there are aspects of honey that mitigate the deleterious effects of the fructose.) Similarly, I don't skewer my meat on a stick and roast it over an open flame.
Heck, fruit consumption is an obvious example of something that nearly all apes and then hominins would have done for millions of years as much as possible, but I'm not convinced that it is ideal for health. I think of fruit bearing plants as nature's drug dealers who produce fructose to get us hooked so we keep coming back to spread their seeds with a nice serving of fertilizer. Sure there is some good in it, but I'm not currently of the mind that it's optimal. Fruit consumption has to be one of the behaviors that can be traced back the furthest and which obviously aided in our species coming into existence and reaching this point, but for me in 2011, it's likely disadvantageous.
On the other hand, I'm a strong proponent of consuming starches of a non-toxic type and in the correct amounts. Glycolysis is one of the oldest metabolic pathways for all life on Earth. Everything from yeast to humans are storing glucose in the form of glycogen for energy, so I find this "paleo" idea that we should avoid all glucose and only consume fat and meat without any significant amount of physiology geared toward carnivory to be quite strange indeed. Perhaps we are confusing "can" and "should."
I would wager that nearly all species that have ever existed have some percentage of what they eat or do that is hindering their ability to procreate in some way, but because the bulk of what they do is conducive to living long enough to reproduce, they persist in spite of that which is harmful. It's the positive net value of your existence as a whole that is judged on an evolutionary scale, not whether you did everything correctly. Well, I'd like to opt out of reproduction and simply be very healthy for a very long time. My path will thus diverge from what has come before because I have very different goals.
All told, however, there is obviously far more in paleo that is consistent with our design than there is in contemporary lifeways, but I rather like being parasite-free and utilizing modern technology when it's clearly advantageous.
Edit: One other point I think is important is that there is nothing consistent about "paleo" in general. A survey of contemporary HGs might yield a general consistency with macronutrient breakdowns and so forth, but the degree of variation based on the particular ecology, season etc. is huge. I'm highly skeptical of an approach that seeks out something that existed and then attempts to make the determination that because one tribe did something, then all humans will thrive doing it.
