I think your criticisms are valid. Generalizations have their purpose, but also their limitations.
I have seen a number of studies differentiating east and west Africans, but I don't recall anything similar differentiating Caucasians (other than that the European-specific gene pool is thought to have originated with about 100 individuals). White people are spread out over a large region historically, and so it would seem reasonable to think there might be significant physical differences.
Latspread said:
I still don't see how white advantage in endurance begets white disadvantage in short sprinting.
The human system cannot optimize both endurance and short sprinting simultaneously. There is a trade-off. Caucasians tend to adapt better to training, while west Africans just don't develop stamina as well. The Caucasian and his many receptors will develop lots of muscle --- but it will be muscle that is adapted to the kind of training he is doing --- and some of this will be endurance muscle rather than sprint muscle. The Caucasian may develop more total muscle, but perhaps less sprint muscle. The west African simply can't develop endurance muscle, and so all of his development goes to what is left by default.
Conventional sprint training requires a fair amount of endurance. My guess is that this kind of training tends to stimulate more endurance muscles in the Caucasian (and he thus ends up as a 400 or 800m guy rather than a 100m), while the west African just does not develop a similar endurance. Adjusting training methods could change the situation so that the Caucasian does not inadvertently become a distance runner with the strength of a gorilla. This would require short very intense activity, like plyometrics. The downside is that injury is more likely.
Black people (whether African or in other locations) have bodies that are made to dissipate heat, and thus tend to have long limbs and non-deep chests. Northern Europeans (or peoples in other cool regions) would tend to be somewhat the opposite. The large lungs tend to be encased in large muscular torsos, and thus make a lot of weight to carry.
Long limbs in themselves are not necessarily advantageous unless there is strength to power them. Even if there is strength, the long limb will make for less quickness, while the proportionately small lungs will make for less endurance. However, somewhere in-between the lack of quickness and lack of endurance, the person with long limbs and good strength (whether via PEDs or otherwise) has a good possibility to be a fast runner.
Some of the very best sprinters were definitely not long-limbed. Michael Johnson and Maurice Greene come to mind. The most important asset of a race horse is its chest/lungs and trunk.
I admit that most of these generalizations are based more on wildlife studies than human populations. But even if human beings follow these physical patterns, then you make a good point in that Caucasians live in many different regions, and thus it would seem reasonable to expect that there are many different body types.
Edited by: Observer 
