"on the assumptions that each cluster of alleles can be entirely assigned to a single migration phase, and that its age approximately corresponds to the timing of the migration event . But are these assumptions justified?
As a matter of fact, hardly so. A mutation is a biochemical change affecting a fertile cell in an individ-ual; a migration is a demographic process affecting many people. The two phenomena are independent; people of blood group A did not expand all over the world at the same time, right after mutation occurred, and that is also the case for mtDNA and Y chromosome mutations.
(...) Furthermore, the definition of haplogroups is arbitrary, depending on what one considers their founding mutation; by splitting a haplogroup in subhaplogroups of inferior order, clusters can be constructed with any lower time depth. Finally, the average coalescence time of two sequences sampled from two diverging populations is older, or much older, than the split of the groups "
http://www.ncbi.nlm.nih.gov/pubmed/24861858