Even if you take the human evolutionary tree transitional forms between the different human species are absent and you have very rapid speciation taking place in less than 6 million years.How do you mean transitional forms between human species are absent? http://humanorigins.si.edu/evidence/human-fossils You do understand there's not supposed to be any bridge between concurrently existing types - only common ancestors of divergent types. 6,000,000 years is hardly an eye-blink! All this http://popchartlab.com/products/the-diagram-of-dogs happened in the less than 10,000 years that humans have been breeding dogs. Since canines - though not modern style dogs - may have been associated with humans for as much as 32,000 years, I'm allowing that the domestic canine species must have undergone some modifications during the whole of that association: that's 16-20,000 generations of dogs altogether; no more than 6,000 generations of purposeful breeding. Why do you consider those changes in hominid skull shape, in a variety of environments, over 350,000 generations, as very rapid?
(I'm counting 2 years for canine and 20 years for human breeding maturity. For most of the time period, both species were probably reproducing at an earlier age; closer to 15 years per human generative cycle - which makes it even more: maybe 357,000 generations. Probably 160,000 since the earliest identifiable human. That's plenty of scope for cumulative changes. Consider: we've only had 250 generations since Noah.)