Ergaster

Much of what you say here is true. Humans did not acquire all their traits in one fell swoop; among the first seems to have been bipedalism. The evidence suggests that australo bipedalism was not identical to modern human bipedalism, but if we get over the tendency to think of all hominins in terms of modern humans and think of them in terms of themselves, there is no reason to believe it *should* have been identical. Big brains came later, and really big brains a LOT later.

The case of Turkana Boy is interesting. This is clearly the first hominin species in which body proportions and sexual dimorphism (the size difference between males and females) approaches the modern condition, but the brain capacity does not. It had long been assumed, too, that tooth development was closer to that of modern humans than australos (Homo erectus being a sort of human "rubicon")...BUT...it turns out that when the Turkana Boy and a Java erectus were studied, they didn't show the modern pattern of dental development either. And since tooth formation and development is tightly correlated to life history variables, Homo erectus probably did not grow, mature, or have age of first reproduction (among other things) in the modern human pattern, either.

See:

Dean et al. 2001. Growth processes in teeth distinguish modern humans from Homo erectus and earlier humans. Nature 414:628-631.