The dominant theory of speciation is that it results from a slow accumulation of genetic mutations.

ECONOMIST: Genes are not all there is to heredity

In addition, there is growing circumstantial evidence for hybrid speciation in Ragoletis fruit flies, swordtail fish and African cichlid fish.

BBC: NEWS | Science/Nature | Two species become one in the lab

Boeke says that when more of the yeast genome is synthesized, researchers will be able to use the system to study evolution and speciation.

FORBES: Yeast Goes Synthetic

The fact that it has human-like features suggests that human-chimp speciation may have occurred over a long period with episodes of hybridisation between the emerging species.

BBC: NEWS | Science/Nature | Evolution's human and chimp twist

So the epigenetic hypothesis of speciation has an edge.

ECONOMIST: Genes are not all there is to heredity

The actual moment when a "daughter" species can (or will) no longer cross-breed with the population from which it sprang (the definition of speciation) is almost impossible to pinpoint, let alone to witness.

WSJ: Matt Ridley on the Possible Formation of a Species | Mind & Matter