Sometimes, I don't know how to write about important matters. Please bear with me, because this subject is far more important than it might initially seem.
When most people encounter the word
species, it is either in the context of a biological discussion, or the word is used as a metaphorical borrowing from discussion of that sort. It actually has more general meanings, the broadest simply being class of things of shared characteristics. But what concerns me here is indeed its biological sense.
Most people who have any notion at all of the word derive their understanding of the biological signification from a combination of observed use and whatever was told to them by middle- and high-school texts of alleged science. Many of them know that organisms are categorized hierarchically, and that species is a finer category than genus. But, if asked to describe the classification of animals as different, say, as are cats and dogs, far more people would descibe them as of
different species than as of
different family or as of
different genus. There is an inferred sense that difference in species is rather fundamental.
The Shorter Oxford English Dictionary gives the biological sense thus:
A taxonomic grouping ranking next below genus and subgenus, which contains organisms that are uniquely distinguished from others by certain shared characteristics and usu. by an inability to interbreed with members of other such groupings; such a grouping as denoted by a Latin binomial, and freq. subdivided into subspecies, races, varieties, etc.; the organisms of such a grouping.
That bit about
inability to interbreed is a bit loose; for example, most biologists would classify horses and donkeys as of different species, though they can produce offspring. However, a striking characteristic of those offspring is that they cannot themselves produce further offspring. The infertility of those offspring is usually cited towards explaining the speciation.
In any case, The SOED hedged with that
usu. because some biologists categorize animals as of different species though they can interbreed down through indefinitely many generations, as in the case of coyotes (C. latrans) with wolves (C. lupus).
Over some decades, anthropologists disagreed over whether to classify Neanderthalers as a distinct species, H. neanderthalensis, or as a sub-species of H. sapiens. As there was no way to observe potential interbreeding, early disagreement turned on issues of overt morphology — the shapes of skulls, dentition, &c. But then interbreeding became, in a sense, potentially observable as it became possible to extract and analyze DNA from remains of Neanderthalers. Initial results (quite surprising to me) suggested no interbreeding, and it became more commonly accepted that they should be considered a distinct species. However, when later genetic evidence began to show the presence of Neanderthaler genes in some modern populations of H. sapiens, the practice of treating them as a distinct species was not universally abandoned. It is still common to classify Neanderthalers as a distinct species, though this implicitly means that
species is not being used with the usu. signification. And when, far more recently, a similar archaïc population, the Denisovans, were distinguished, it became fairly common also to categorize them as a distinct species, though their genes are likewise found in some modern populations of H. sapiens.
But, again, when most lay-people hear or read the word
species, they are imagining a quite significant distinction. And when they hear and read of Neanderthalers or of Denisovans as distinct
species, they infer that these people were not human. Here are three example articles that I quickly found of journalists doing just that in the case of Neanderthalers or in that of Denisovans:
As these archaïc populations are extinct, there may not seem to be any more of a social issue here than there typically is with misunderstood science. But a problem is coming right at us. And it's associated with the point that the genes of archaïc populations are found in modern populations — in different distributions. Take, for example, this article:
The author or authors blithely refer to the Neanderthalers, to the Denisovans, and to an additional, hypothesized archaïc population as distinct
species without explaining whatever is there meant by the term. A large share of readers will regard the archaïc populations as not fully human, and infer that different ethnic groups have more or less genetic material that is not fully human. It will be inappropriately inferred that some ethnic groups are thus less human or more human than are others.
Anthropologists and biologists who talk with lay-persons, and especially with journalists and with other informal educators, need to emphasize the arbitrariness in use of the word
species, and these scientists need to impress upon their audiences that the word should be avoided or explained in all popular-science journalism that touches upon our relationships with archaïc populations.