You're right, on its on it is meaningless. This is within the scope of fitness. I should add that I am 6'2 and 175 lbs, do resistance training and endurance cycling and running. I stick to a paleo approach to life and nutrition. My goal is to be functionally fit, have a higher quality of life, look better and live longer (but only if the quality is there with the longevity).
With regards to the weak argument I have seen between paleo man and longevity, please consider the following logical fallacy.
"Confusion of correlation and causation: (e.g., More men play chess than women, therefore, men make better chess players than women. Or: Children who watch violence on TV tend to act violently when they grow up.) But does television programming cause violence or do violence oriented children prefer to watch violent programs? Perhaps an entirely different reason creates violence not related to television at all. Stephen Jay Gould called the invalid assumption that correlation implies cause as "probably among the two or three most serious and common errors of human reasoning" (The Mismeasure of Man)."
Here's a good article to explain what I'm talking about.
Now so far I am doing well with this approach. My average BP is 104/70, my resting heart rate 58, my heart rate recovery 65, my blood sugar levels alway steady in the 80 - 100 range, good oxygen level in the blood, plenty of energy throughout the day, good sleep, ability to run and bike 100 miles a week and I've had full blood work done very recently and it's all in the norm.
I had posted to another topic about the last remaining fat on my body which is right in my mid section. It's not very much fat at all, hardly noticeable, but I'm hoping it will eventually fade away.
Within the context I've given here, I hope 15 percent body fat is decent. Even though that's not my main goal, my theory has been that doing it paleo will get me what I am seeking above. For me, it seems probable that the diet and lifestyle the body evolved with for the most time should be optimal (when combined with other modern technology and science). I may be wrong though which is why I am testing the idea with my own body.