"The humeral fragment from Kanopoi, with a date of about 4.4 million years, could not be distinguished by Patterson and myself in 1967 (or by much more searching and analysis by others since then). We suggest that it might represent Australpithecus because at that time allocation Homo seemed proposterous, although it would be the correct one without the time element".(Bones of Contention, Lubenow, Dec. 1992, pp. 56-57)
"The humeral fragment from Kanopoi, with a date of about 4.4 million years, could not be distinguished by Patterson and myself in 1967 (or by much more searching and analysis by others since then). We suggest that it might represent Australpithecus because at that time allocation Homo seemed proposterous, although it would be the correct one without the time element".(Bones of Contention, Lubenow, Dec. 1992, pp. 56-57)
The elbow (distal humerous) like KP 271, by itself, is not much good for fine definition. There are a lot of other parts of the body which are much better-teeth are among the best, face and cranium excellent, femur and pelvis excellent. But ribs and a few other of the bones are less diagnostic.
But even with these parts, with a large enough sample you can use multivariate statistics and come up with some good data.
A quick check of the web shows that the KP 271 site has yielded a lot more specimens.