Not that surprising when you consider, as the paper does, the explosion of very meaningful traits such as the ability to digest lactose and various anti-malaria adaptations e.g. Sickle Cell and the Duffy-null mutation.

It's just controversial for obvious reasons. The notion that human groups may have meaningfully evolved in different ways over the past 10,000 years, and may still be evolving, is an unpopular one on both ends of the political spectrum.