Bogoras describes the people of this book in the vocabulary of nineteenth-century physical anthropology — cephalic indices, faces "strongly Mongolian in outline", bodies measured against those of "Caucasians". That framework is not a superseded answer so much as a superseded question. The traits it measured do not partition human populations into types, and where northeast Siberians came from is now read from genomes and from linguistic reconstruction instead: see Sikora et al., "The population history of northeastern Siberia since the Pleistocene" and Flegontov et al., "Palaeo-Eskimo genetic ancestry and the peopling of Chukotka and North America".

Worth knowing before reading chapter II as its author's racial theory: it is not one. The Jesup North Pacific Expedition was designed and directed by Franz Boas, whose programme set historical contact against race as the explanation of why peoples resemble each other, and Bogoras's comparisons here run consistently in one direction — narrowing the distance between the Chukchee and Europeans rather than widening it.

What the book is doing

Chapter II opens on the physical type of the Chukchee, and 1-055 gives the method outright: "As ascertained from anthropological measurements", followed by a cephalic index. The measurements were part of the Jesup North Pacific Expedition's brief, and 2-073 records what taking them was actually like in the field.

The categories Bogoras reaches for are Mongoloids and Caucasoids, and the entries for both, with Physical anthropology, say what this edition does and does not claim by recording the words at all.

Two of the book's uses are worse than merely dated. 3-060 explains the childlessness of Russian–Chukchee marriages on the Kolyma by "the exhaustion of vital force", with the scarcity of "blood really Russian and Caucasian" as the reason; that is degeneration theory, not observation. 3-093 calls a man "a specimen of some lower type of man". Both are worth reading as evidence about their author and his period, and neither is evidence about anybody described.

Modern Follow-Up

Sikora et al., "The population history of northeastern Siberia since the Pleistocene" sequenced ancient genomes from northeastern Siberia and described the deep population history of the region, and Flegontov et al., "Palaeo-Eskimo genetic ancestry and the peopling of Chukotka and North America" traced Palaeo-Eskimo ancestry into Chukotka and North America — including into speakers of the Chukotko-Kamchatkan languages, which is where the genetic and the linguistic questions meet. Glottolog: Chukotko-Kamchatkan is the current classification of that family, to which Chukchi belongs.

Two things are worth holding onto from the contrast. The modern account is about populations and their histories of movement and contact, not about types a face can be sorted into; and it reaches conclusions Bogoras's own framework had no way to state, while confirming the thing his fieldwork was actually organised around — that the peoples on the two sides of the Bering Strait are connected by history.