Despite the fact that N appears lower down on this map than M, it's important to recognize that both are "sister" clades, branching off from the same "mother": L3 -- now found only in Africa. If M and N are sisters, does this mean there were two different Out of Africa migrations? I don't know enough about population genetics to get into this question very deeply, but perhaps Maju, who knows a lot more than I, will be willing to chime in with some suggestions. I found an interesting reference to this issue in a paper by Luca Cavalli-Sforza and Marcus Feldman, The Application of Molecular Genetic Approaches to the Study of Human Evolution, dating from 2003.
Having established, however provisionally, a baseline for the consideration of the physical and cultural nature of the population ancestral to M, N, and L -- what I've been calling HBP and HBC -- we are now in a position to speculate further regarding the physical and cultural characteristics of their descendants, the Out of Africa migrants. This will not be anywhere near so easy, however. If you look carefully at the phylogenetic tree reproduced above, you'll notice an important difference between the uppermost branches, labeled L, and those lower down, dominated by M and N. Though not indicated on the diagram, the deepest branches, especially L0, L1, and L2, are dominated by Bushmen groups and both of the major Pygmy groups, Eastern and Western. The simplicity of this picture, along with the equally clear musical evidence, has made it relatively easy to characterize HBC on the basis of what we know about these three groups, using the triangulation method already described. The many branches emanating directly from M and N present a very different picture, however, with far less structure. Unlike the situation with L, it's not at all clear where we can look if we wish to triangulate, or even quadrangulate or quintangulate (have I just invented two new words?).
We can, of course, look backward to HBC for signs that certain ancestral features might have survived in HMC. But we will also need to draw on what we know about a great many indigenous societies in many different parts of Asia, Oceania, Australia and Europe as well. And since there are so many differences among so many of these groups, our task will not be easy. It is nevertheless, in my opinion, possible to develop some very interesting and to some extent testable hypotheses regarding both HMP and HMC, and to the extent that we can do so, we will have established another important baseline for the study of human history.