Yet another way in which the French were inferior - I don't think that's necessarily a very good example of the historical size of H. sapiens. By way of a counterexample, the minimum height requirement for the Roman army - during the time they were stomping all over the Frenchman's inferior ancestors, no less - was 5'5" for the infantry, and 5'10" for cavalrymen. And they never had much trouble filling their ranks by the tens of thousands, suggesting that even if 5'5" was somewhat taller than average, it was hardly three standard deviations away from the mean, if you follow me.
Plus, if you assume human growth rates for the Turkana specimen, which is generally believed to have been about 11-12 years old, and around 5'3" at death, you wind up with an adult height in the neighborhood of 6'1". Which may or may not have been exceptionally tall for H. erectus, but when life is a competition, having a few exceptional individuals on your team can sometimes make a significant difference...
At different times in history, some human populations have been consistently well-fed. They usually managed to grow large in these cases. The Vikings at their peak seem to have eaten well and grown robust. The early settlers in North America were full of admiration for the physiques of the Mohawk warriors. Hawaiian royalty made being well-fed and large a status symbol. Some of them got quite impressive.