"In short, genetic drift is the application of statistics to genetics…When we’re dealing with genetic drift, the first helpful fact to recognize is that we’re not dealing with scientific laws. Instead, we’re dealing with probabilities."
He goes on to discuss genetic drift in humans then the equid group of zebras, horses, donkeys/asses as examples. He further explains heterozygous and homozygous parents, for certain traits, and the probability of their offspring's inheritance of these certain traits. Then with genetic isolation different groups(species) can develop. He concludes:
"In summary, one of the keys to understanding the origin of species is genetic drift—the simple application of statistics to basic genetics. If Noah brought heterozygous ancestors on board the Ark, then the formation of new species—at a rapid pace—was virtually guaranteed. And if this process was virtually guaranteed, then creationists are sitting in the driver’s seat when it comes to the central question in the creation/evolution debate."