My memory on this could be faulty, but I seem to remember that a study of the population of this town in Italy was able to trace the gene in question to a single common ancestor not that many generations ago. It would appear that, in this case, the continued diversification of our species is going to point the way.
For those wanting to turn this into another flame war on the evolution topic, be aware that this is not the rise of a new species. This is only an adaptation in an existing species and neither proves nor disproves evolution or creation.