Popularity of hominin species names

I was curious about the use of Homo ergaster over time. It seems to me that fewer and fewer paleoanthropologists have been using it over the last few years. My perception (I’ll share later) is not borne out by the Google Scholar statistics: More scientific papers during the last five years have mentioned Homo ergaster than in any previous period.

As I was looking, I checked out Google Ngram Viewer and found this alarming result:

Hominin species names according to Google ngram viewer
From Google Ngram Viewer

Wow.

Google Ngram Viewer tracks the use of words or phrases in books, and goes only up to 2008. It’s pretty striking to see Homo ergaster had nearly overtaken Australopithecus afarensis in book mentions. These are not only popular books, they are also textbooks and technical books, so it’s hard to generalize about the causes of the trends, which are overall very small compared to other hominin species (such as Homo erectus).

Here is another interesting comparison, considering that the main descriptive papers about Ardipithecus ramidus were not released until 2009:

Hominin species names according to Google ngram viewer, including Orrorin and Sahelanthropus
From Google Ngram Viewer

Some of the decline in Ardipithecus ramidus after 2000 may have been caused by the availability of Orrorin tugenensis and Sahelanthropus tchadensis as “first hominins” – few popular books about human evolution can avoid naming the earliest known hominin fossils.

Homo habilis and Homo erectus dwarf the popular usage of any of these other species names. Books have used Homo habilis three times more than Australopithecus afarensis at its peak, and Homo erectus appears six times more often.

The rise of Homo ergaster after 1990 is in part explained by the rise of popularity of cladistics in paleoanthropology. That trend is also evident in two other species names:

Hominin species names from Google Ngram Viewer, with Homo heidelbergensis and Homo neanderthalensis
From Google Ngram Viewer

By 1980, the names Homo neanderthalensis and Homo heidelbergensis were at the nadir of a five-decade-long decline. Homo neanderthalensis was discarded mainly for the non-taxonomic “Neanderthal” (or “Neandertal”), while Homo heidelbergensis lost ground partly to “early Homo sapiens”, and later (after 1970) to “archaic Homo sapiens”. But after 1990, cladists had revived those formal taxonomic names, arguing that both represented real species of Pleistocene humans. The “out of Africa” perspective on modern human origins helped to promote the hypothesis that the formation of new species was a common mechanism of evolutionary change throughout the Pleistocene. Homo heidelbergensis was the foremost beneficiary of this viewpoint. My readers know that I don’t like either of these names and prefer the non-taxonomic equivalents.

The same rise of cladistic methodology and its accompanying philosophy has spurred the use of the term “hominin” instead of the earlier term, “hominid”. By 2008, “hominin” was used approximately one third as often as “hominid” according to the Ngram Viewer.