1) You believe that it's an inability to go barefoot as to why people where shoes? People where shoes because that is what this society calls for. People run in running shoes because a) they are told that they need to a b) because they don't have the strength/technique that is present in unshod populations.
2) As to evolution and running:
http://www.ultrawalking.net/entrenos/evolutionrun.html
"Endurance running, unique to humans among primates, evolved at least 2 million years ago and enabled human ancestors to hunt and scavenge over large distances. That, in turn, probably proved decisive in their pursuit of high-protein food for development of larger brains.
The evolution of a physique for long-distance running is what made humans look the way we do now -- whether winning a marathon, nursing a strained Achilles' tendon or sitting on an ample gluteus maximus in front of the television.
The apparently crucial role of running in human evolution, overlooked for the most part in previous research, is being proposed today in an article in the journal Nature by two American scientists.
Although walking upright first set early human ancestors apart from their ape cousins, the scientists write, it may have been the ability to run long distances with springy step over the African savanna that influenced the transition to today's human body form.
Endurance running, unique to humans among primates and uncommon in all mammals other than dogs, horses and hyenas, apparently evolved at least 2 million years ago and probably enabled human ancestors to hunt and scavenge for food over large distances. And that, in turn, probably proved decisive in their pursuit of high-protein food for development of larger brains.
Origins of Genus
The scientists, Dr. Dennis M. Bramble of the University of Utah and Dr. Daniel E. Lieberman of Harvard, reported that their analysis of the fossil record showed striking anatomical evidence for the capability of prolonged running in the Homo genus as early as 2 million years ago.
"Today, endurance running is primarily a form of exercise and recreation, but its roots may be as ancient as the origin of the human genus," the scientists concluded in the article.
Bramble, a professor of biology and a specialist in the biomechanics of animal locomotion, said, "Running made us human, at least in an anatomical sense." Bramble said he and Lieberman were "very confident that strong selection for running was instrumental in the origin of the modern human body form."
Other paleontologists not involved in the research praised the hypothesis as an important insight into the apparent significance of long-distance running in human survival and evolution. But they raised questions about what stimulated the physical transition that led to this human capability.
Long Legs, Short Arms
By 2 million years ago, Bramble and Lieberman noted, early species of the Homo family, beginning at least with Homo erectus, had long, slender legs for greater strides. They had shorter arms and a narrower ribcage and pelvis. Their skulls included features to help prevent overheating. A ligament attached to the base of the skull kept their heads steady as they ran.
Tissues do not fossilize, but traces of muscle and tendon attachment points on bones of early species revealed an extensive network of springy tendons along the back of their legs and feet. That network includes a well-developed Achilles' tendon that anchors the calf muscles to the heel bone. Tendons store and release elastic energy during running but were not needed for ordinary walking.
There also was the gluteus maximus, the muscle of the buttocks. Earlier human ancestors, like chimpanzees today, had pelvises that could support only a modest gluteus maximus, nothing like the strong buttocks of Homo.
"Have you ever looked at an ape? They have no buns," Bramble said.
Running and Reproductive Success
"Your gluteus maximus stabilizes your trunk as you lean forward in a run, said Lieberman, a paleontologist. "A run is like a controlled fall, and the buttocks help to control it."
The two scientists speculated in the article and in interviews that running by early human ancestors was more than simply a natural step, so to speak, beyond upright walking. These apelike ancestors, the scientists noted, were walking almost 3 million years before they became runners and began to assume more modern physiques.
In ancestors like the Australopithecus genus, famous for the 3.2 million-year-old Lucy skeleton, the physical characteristics favoring running were either absent or underdeveloped.
Somehow, the scientists said, those early ancestors who developed primitive running attributes must have improved their chances of survival and reproduction. They were not as swift in a sprint as their contemporary four-legged competitors for prey. But their ability to run greater distances than other predators must have been an advantage in making a kill or at least scavenging the kills of their swifter rivals."
2) I am saying more feedback is better, the same as less processed foods is better. Sure, flats do decrease your perception of the ground, but far less than your standard bulky trainer. Everything is a spectrum, and the closer you are towards unshod, the stronger and healthier your feet will be.
3) Africans who grow up running around, being active unshod in their youth engrain in themselves highly efficient mechanics (generally), during that crucial motor development phase. Once that's there, it's pretty firmly set and hard (but not impossible) to screw up. Yes, there are some highly efficient people (like El G) that do running in trainers. But he does an awful lot of drills, and quite a bit of running in spikes/flats. I'm not saying that it is impossible to be so efficient and run in trainers: I am saying that someone like El Guerrouj is incredibly efficient in spite of wearing the Pegs.
Running in flats (properly) will have a dramatic effect on form (depending on the level of efficiency to begin with) because efficiency is so encouraged -- people learn to be much lighter on their feet because they need to be. The same way the ultra cushy shoes allow for poor form and weak muscles.