Very interesting article, but why do western scientists always do that? Make a claim about "all people in the world, except these Kenyan women"? It simply isn't possible that these scientists examined or have seen or even know about how most people in the world walk, especially all the other people in the world who carry loads on their heads. A silly claim. I'm sure there are a lot more efficient walkers all around the world and over the millennia than these scientists could possibly imagine. But just because it is published in "Nature" and "The New York Times", that somehow makes it informed and true. Pah!
I remember going to a lecture by a famed Harvard expert on geckos. He showed slides of geckos he had encountered around the world and talked about their habits. Then he made a claim that astounded me, "So far, science has not been able to determine where geckos hide out during the day." WHAT?!?! Any sun-browned, mosquito-bite-covered-legged kid in Japan or anywhere in Asia (and most probably South America Africa, too, I surmise) can tell you right off the bat where geckos hide during the day. Just peel off loose strips of bark, open two leaves pressed together, or flake off a flat piece of stone or concrete from a wall, and there you have your geckos. What stone had this scientist been hiding under all these years? And why in the world did he never bother to ask the locals, especially the kids, where the critters were? Too high in his Harvard seat to stoop to such rustic noodle fare? Again, "Pah!"