Despite that, you rarely see a cave man depicted with a lean stature. Not even my Scottish and Cherokee ancestors are known for being lean.
Hmm, I'm not sure about that. By lean, do you mean emaciated? Or rippling muscles? Or simply, as I think it was throughout most of human history, with little extra body fat. If you look at any old photographs of Americans just 150 years ago, you will very rarely see overweight people. Most of them didn't have bodies of the kind you see in "Sparta" or aerobics competitions, but almost everyone was lean. And if you look at old photos of Native Americans (I have Gullah ancestry from South Carolina, a mix of Cree and escaped slaves who lived in isolation until fairly recently) from throughout the country, you never see any overweight people. Now I'm talking from 150 years ago and more, not more recent history, in which diets worldwide were drastically changed by the sudden explosion of industrial production. I also have Filipino ancestry and have lived in Japan for most of my life, and people in the Philippines and here are almost never overweight. Almost everyone is quite lean. I have traveled throughout the world and most people in most of the world are lean. The obesity problem in the States right now is very much an anomaly, and not the norm by any measure. And I think it very much has to do with the huge amounts of grains and sugar and sheer amount of food that people eat. Though, sadly, as processed food consumption increases in many parts of the world, obesity is beginning to spread everywhere. Nearly all of it is due to processed foods, sugar, and grains.
I also do a lot of walking in the mountains in Japan. Throughout my life (I've been here for 27 years over a span of 41 years) I have seen extremely fit and healthy Japanese who do very strenuous mountain walks without all the huge amounts of eating that people talk about so often here on BPL. I once met a 75 year old mountain woodcutter who everyday walked about 20 km in very steep, rugged terrain, plus shinnied himself several times a day during those walks up and down the trunks of cedar trees (including coming back down headfirst), and all he ate for lunch were two tangerines and a small rice ball with a pickled plum inside. That kept him going all day long. His muscles were ropey and extremely well defined and he was indefatigable. I once saw him carry a rope and wood slat pack with an enormous load of wood that I couldn't even lift. I don't know how he did it. I suspect he had never eaten much throughout his life. He would have been astonished to see the kinds of meals so many Americans eat.
As to images of cave men, I beg to differ. Most images I've seen of them are of burly, heavy browed ape-like brutes who certainly are very lean and muscular (as are wild apes. Gorillas seem to be overweight, but actually that is all the vegetable matter fermenting in their stomachs... humans can't eat a gorilla diet). I'm not talking about Homo erectus, but of Homo sapiens, our direct ancestors who are identical to us, in fact are us (recent discoveries in genetics have found that we also have neanderthal genes and characteristics among us, too). The main problem with depicting them in images is that no one with a camera or good drawing skills was around then to record them, so we simply don't know. But from all the archeological evidence, they were exceptionally fit and very lean. Very few of them had any of the modern afflictions we suffer from today, like cardiovascular diseases, tooth disease, lifestyle diseases like diabetes or obesity. They were also taller than people of the first few thousand years following the development of agriculture, and their brains were slighter bigger than our's are today. Nearly every study done of hunter-gatherers today have found them to be very fit and lean, with almost no modern diseases. Diabetes and obesity was unheard of among Native Americans until the introduction of the European diet... now it is the highest rate in the world. If you see people like the tribes in the Amazon or New Guinea who seem to be overweight, that stomach distention is very often is caused by kwashiorkor or protein deficiency, something, surprisingly, that is hard to get in rain forests.
I guess the question we all have to ask is, do we want to "look" fit or "be" fit? We really have to redefine what "fitness" means. To me, while it is nice to have rippling muscles, I'd much rather feel energetic all day, sleep well at night, eat just enough to keep my body running in top well-being, including being able to fend off infections and occasional stress well, occasionally eat something just for the pleasure of it, live a very long, fulfilling life, have healthy children, and enjoy a nice, challenging hike every now and then. To me that is health and fitness.