was the discovery that the North Pacific and North Atlantic populations are also distinct, and that the North Pacific species is more closely related to the southern right whale than to the North Atlantic right whale.The authors of one of these studies concluded that these species have not interbred for between 3 million and 12 million years.

In 2001, Brownell et al. reevaluated the conservation status of the North Pacific right whale as a distinct species, and in 2002, the Scientific Committee of the International Whaling Commission