Homo sapiens evolved without weightlifting machines, jump ropes, and other modern inventions. Assuming they ate the diet that human beings are suited to -- rich in animal products and low in carbs -- and lived their normal lives, they were lean and muscular. Although pastoralists are not hunter-gatherers, they rely enough on animal food and do not even cultivate let alone consume the carby junk that farmers do, like corn, potatoes, wheat, rice, etc. And they are still physically active. It's only when people started farming that their health went down the tubes -- they got shorter, had weaker bones, and so on.
Still, some people in agricultural societies ate well, and in the capitalist societies up until about 1980 an increasingly large fraction of the population could afford a diet brimming over with animal foods. In our species' beginning, we might have gotten muscled by hurling projectiles, moving heavy obstacles out of the way, giving others a boost into a tree, pulling ourselves into a tree, sprinting toward a prey animal, sprinting away from a predator animal, and so on. Once capitalism set in and we no longer lived that way, we would have played sports, lifted heavy things for a living, and other activities that are not so different from what a hunter-gatherer would have done.
Once people started going to the gym, though, they started to look weird. I can't pinpoint exactly what it is about gym bodies that look off -- it's a gestalt impression. But every image of the ideal male body I've seen from the ancient Mediterranean through the movies of the 1970s and even somewhat of the '80s shows a very different looking person than the gym guy. To show what I mean, here is a 16th C. Italian sculpture of Ganymede, a mythological figure famed for his beauty, and here is a random shot of present-day gym dudes.
What are the differences, and why causes them? A computer program designed to recognize patterns could do a better job if it were fed a bunch of images of each type and then told us along which dimensions they differed the most, but I'll try to flesh out some of my overall impressions.
First, the gym guys are fatter. In some parts they have little body fat, but if you just look overall, they're not as lean as Ganymede. It would be the same if I compared them to a group of hunter-gatherers or pastoralists, who are always lean and cut. I attribute this to the gym guys' diet -- obviously they're lifting weight to build muscle, but they probably eat too much carbs, which boosts their insulin level and keeps more fat locked in fat cells instead of being burned for energy.
Also, their skin looks pretty matte, not glistening. Here I can't compare with Ganymede, but think of Stallone in the early Rocky movies. It's not just sweat, since it's true even when they're not working out. I think what's going on here is a lack of vitamin A among the gym guys. This vitamin is necessary to maintain the health of your epithelial cells -- anything on the surface, such as your skin, but also "inner surfaces" like your digestive and respiratory tracts. Low vitamin A levels will make your skin look like hell.
To build muscle, you need to eat protein, which gets broken down into amino acids, and these are re-assembled into human muscle protein. Vitamin A gets used up in this process, so if you eat a lot of protein and are lifting weights, you will probably deplete your store of vitamin A -- unless you get a decent amount from your diet.
There's really only one source for it, and that's liver. Of course, most gym guys don't eat liver in any form, unlike what regular people in capitalist societies used to do until very recently. Hunter-gatherers have good access to it, and even pastoralists do to a lesser extent. Vitamin A also comes from dairy products, although in far lower concentrations, so pastoralists make up for their relative lack of liver by consuming a lot more dairy. Eggs, too, are about as good a source as dairy. But unless these gym guys are eating a dozen eggs and a pound of Gruyere cheese or clotted cream a day, they're not getting enough vitamin A. (This vitamin only comes from animal products. A precursor to it comes from plants, but the conversion process is so inefficient that you'd have to munch a room full of spinach just to get enough -- like cows that chew grass all day.)
Next, their chest muscles are way too overdeveloped. You never saw these kind of man boobs before gyms existed. They have somewhat defined abdominal muscles, but not really anything on the sides of the torso -- again, I'm not talking something monstrously beefed up, but something lean and cut like Ganymede shows on his sides. You can't really see the definition of their ribcage, but that may just be the fat problem mentioned earlier. I also don't notice a clear distinction between the biceps and triceps. It's hard to see if that's there on Ganymede, but go watch a Dirty Harry movie where you see his arms, or when De Niro starts working out in Taxi Driver, or any random picture of hunter-gathers and pastoralists from google images. There's a thin strip between the biceps and triceps that should be flatter against the bone, with the other two standing out more. Gym guys instead have a single bulge on their upper arm. And while their shoulders stick out somewhat, the place where they meet the upper arm is not as cut as you can somewhat see in Ganymede -- or any basketball player's arms.
I don't see any diet-related cause for these muscular differences. I think it's due instead to veering off nature's course for building human muscle. Remember, we evolved in a world without devices meant to isolate this narrow muscle area or that one, so it was not possible to overdevelop one area and leave another one underdeveloped. Pulling yourself into a tree, hurling a spear, and lifting heavy objects all require the coordination of many groups of muscles at the same time. So does swinging a sword or a baseball bat, suplexing another man, dashing to the end zone, and the athletic variety of dancing. Even the workouts that non-jocks used to do (until the gym took over) stressed the entire body, or large parts of it anyway -- pull-ups, push-ups, sprinting, and so on.
Apparently it is impossible to reproduce that in the gym laboratory, although you might think you could just target this narrow set one day, then another narrow set the next day, and so on, until you hit all of the body. How do you know what the proportions should be, though? Should you spend the same amount of effort on every single muscle? Maybe our natural workouts, while using lots of muscles, don't use them all equally. And if they do differ, how would you know which should get more effort than which others? And how do you know which muscles are given a slow-twitch vs. fast-twitch stress in our natural workout? Trying to re-create this suite of nature's harmonious proportions through human artifice is sheer hubris. Maybe some gym wizard could come closer than the typical gym user, but even they still look weirdly out-of-balance.
For their narcissism -- wanting to "look good naked" -- the gym guys are punished with malformed bodies, unlike those who seek the mix of discipline and fun that comes from doing athletic activities, who are rewarded with classical sculpture bodies.
All that I've said applies to females, too. However, throughout our species' existence they were never the launchers of spears, the movers of large rocks, etc., so their natural workout should be different from that of males. In high school I noticed that the girls who played soccer had the best bodies in a feminine sense, probably due to the lack of upper-body workouts, and the lack of fast-twitch muscle stress that would cause them to bulk up (like I noticed on some field hockey and softball players). The least natural looking are the gymnasts, which isn't surprising given how explosive their activities are, and what a large role their upper body plays. Unlike the more demure soccer players, gymnast chicks strut around like guys with their shoulders out and their arms at a distance from their sides, even if they're only 5'1. Just like males, the gym girls end up looking not quite right -- just take a look at any women's fitness magazine cover. They look better than if they were fat, but it's a far cry from the natural softness that girls are supposed to have.
Fortunately, all you need for following the right path is access to a tree with sturdy branches within jumping distance, some flat or hilly land to sprint over, and some heavy shit to throw around. Probably the easiest thing is to find a tree branch that you'd have to jump your highest to reach: squat down, burst up with your arms stretched out, grab hold of it, and then do some chin-ups. Also swing back and forth like a little kid to make sure you don't get too serious. I tried that the other night and my arms felt more fully stressed than when I use dumbbells in my room. I think I'll keep those just for times when I have no time to work out in a more natural setting, but otherwise will try to adhere to what natural selection designed my body to do in order to be in top shape. Guess that's an excuse for more dancing.