However, since the 20th century, indigenous peoples in the Americas have been more vocal about the ways they wish to be referred to, pressing for the elimination of terms widely considered to be obsolete, inaccurate, or racist. During the latter half of the 20th century and the rise of the Indian rights movement, the United States government responded by proposing the use of the term "Native American," to recognize the primacy of indigenous peoples' tenure in the nation, but this term was not fully accepted. Other naming conventions have been proposed and used, but none are accepted by all indigenous groups.
What have the peoples in the Americas been more vocal about since the 20th century?
the ways they wish to be referred to

Anthropologists such as C. Loring Brace, the philosophers Jonathan Kaplan and Rasmus Winther, and the geneticist Joseph Graves,[page needed] have argued that while there it is certainly possible to find biological and genetic variation that corresponds roughly to the groupings normally defined as "continental races", this is true for almost all geographically distinct populations. The cluster structure of the genetic data is therefore dependent on the initial hypotheses of the researcher and the populations sampled. When one samples continental groups, the clusters become continental; if one had chosen other sampling patterns, the clustering would be different. Weiss and Fullerton have noted that if one sampled only Icelanders, Mayans and Maoris, three distinct clusters would form and all other populations could be described as being clinally composed of admixtures of Maori, Icelandic and Mayan genetic materials. Kaplan and Winther therefore argue that, seen in this way, both Lewontin and Edwards are right in their arguments. They conclude that while racial groups are characterized by different allele frequencies, this does not mean that racial classification is a natural taxonomy of the human species, because multiple other genetic patterns can be found in human populations that crosscut racial distinctions. Moreover, the genomic data underdetermines whether one wishes to see subdivisions (i.e., splitters) or a continuum (i.e., lumpers). Under Kaplan and Winther's view, racial groupings are objective social constructions (see Mills 1998 ) that have conventional biological reality only insofar as the categories are chosen and constructed for pragmatic scientific reasons. In earlier work, Winther had identified "diversity partitioning" and "clustering analysis" as two separate methodologies, with distinct questions, assumptions, and protocols. Each is also associated with opposing ontological consequences vis-a-vis the metaphysics of race.
If one samples a continental group, what do the clusters become?
continental

The 1775 treatise "The Natural Varieties of Mankind", by Johann Friedrich Blumenbach proposed five major divisions: the Caucasoid race, Mongoloid race, Ethiopian race (later termed Negroid, and not to be confused with the narrower Ethiopid race), American Indian race, and Malayan race, but he did not propose any hierarchy among the races. Blumenbach also noted the graded transition in appearances from one group to adjacent groups and suggested that "one variety of mankind does so sensibly pass into the other, that you cannot mark out the limits between them".
What can one not mark between the variety of mankind?
limits