If this seems counterintuitive to you, it might be because the space of genetic variation is of very high dimension. See here for more discussion and an illustration.
(Click images for larger version.)
Population Structure and Human Evolution
L. L. Cavalli-Sforza
Proceedings of the Royal Society of London. Series B, Biological Sciences, Vol. 164, No.995, A Symposium from Mendel's Factors to the Genetic Code (Mar. 22, 1966), pp. 362-379
http://www.jstor.org/stable/pdfplus/75457.pdf

Measurement of Differentiation: Reply to Lewontin, Powell, and Taylor
Jeffry B. Mitton
The American Naturalist, Vol. 112, No. 988 (Nov. - Dec., 1978), pp. 1142-1144
http://www.jstor.org/stable/2460361?origin=JSTOR-

Current state of the art, as discussed here. Figure: The three clusters shown below are European (top, green + red), Nigerian (light blue) and E. Asian (purple + blue).

According to the mathematical analysis given in this paper, populations with FST as low as .0001 can be resolved with current technology. (Typical FST between northern and southern Europe is about .006, between Europe and E. Asia about .1 and between Europe and Nigeria about .14 .)