The Biological Species Concept and Human Evolution.

Paul R Ehrlich wrote his paper, 'Has the Biological Species Concept Outlived Its Usefulness' in December 1961, publishing it in the pages of Systematic Zoology, 10(4):167-176 (DOI: 10.2307/241164). The concept was supposedly decisively refuted by Sokal and Crovello in 1970 (Sokal, R.R. & Crovello, T.J., 'The Biological Species Concept: A Critical Evaluation,' The American Naturalist, 104(936):127-153, March-April 1970).

The biological species concept (hereinafter BSC) was developed by the Russo-American geneticist, Theodosius Grigorievich Dobzhansky (1900-75) in 1935 ('A Critique of the Species Concept in Biology,' Philosophy of Science, 2(3):344-355, DOI: 10.1086/286379) and developed by the German biologist Ernst Mayr (1904-2005) in (e.g.) his Systematics and Origin of Species, New York, NY: Columbia University Press, 1942, and defended in Chapter 2, 'The biological species concept', of Species Concepts and Phylogenetic Theory: A Debate, edited by Wheeler, Q.D. & Meier, R., New York, NY: Columbia University Press, 2000, pp.17ff.

Mayr's first sentence is crucial: 'I define biological species as groups of interbreeding natural populations that are reproductively isolated from other such groups.' This leads the present author to define what he terms 'Mayr's Rule (or 'Law')', which is applicable to all sexually reproducing members of the animal kingdom. It reads: 'A male and female of species of different genera may not interbreed at all; a male and female of species of the same genus may interbreed, but their offspring will be sterile; only males and females of the same species can interbreed and produce fertile offspring.'

A concrete example would be that of genus Equus: males and females of E. caballus and E. asinus can interbreed, as can those of E. caballus and E. quagga, or E. asinus and E. quagga, but, in every case, mules, hinnys, 'zorses' and 'zonkeys' are all infertile.

Any apparent exception or exceptions to the rule is/are almost certainly examples of misclassification by zoo-taxonomists. Such misclassifications, if they have been made on the basis of morphological characteristics, rather than on genetics, are, alas, far from being unknown. The fact that introgressive hybridisation can occur between two supposedly separate species of the genus Ursus, U. arctos, the grizzly bear, and U. maritimos, the polar bear suggest that the former may, in fact, be a sub-species of the latter (see: Cahill, et al, 2018).

This is vital to the understanding of human evolution, it seems to me. At the moment, we have a situation where there are no fewer than 22 extinct hominin species recognised by paleoanthropologists (see: Bokma, van den Brink & Stadler, 2012; or perhaps only nine, according to the Natural History Museum in London) - at any rate, we are left with something of an embarras du riches.

Yet it is acknowledged, is it not, that ~2% of the nuclear DNA of modern people of Eurasian descent is Neanderthal in origin, and that 6% of the Tibetan gene pool is of non-modern origin, with an addition of genetic material from the Denisovans, including the allele of the EPAS1 gene on chromosome 2 that enables them to live at high altitudes (Science, 2nd July 2014, DOI: 10.1126/article.22887).

The designation of various extinct hominins as distinct species is based purely and simply on the morphological characteristics of their fossil remains. Indeed, Stringer, C. B., 'Reconstructing recent human evolution,' Philosophical Transactions of the Royal Society of London: Biological Sciences, 337(1280):217-224, 29th August 1992, used Penrose shape comparisons in his methodology, an exercise he repeated (strictly speaking, using Penrose square distances) in 1996, in 'Current Issues in Modern Human Origins,' in Contemporary Issues in Human Evolution, ed. Meikle, W.E., Howell, F.C. & Jablonski, N.G., pp.115-134, Memoirs of the California Academy of Sciences, Volume 21.

The fact that Stringer does not feel he has to apologise for, or in the least bit embarrassed by, a method pioneered by the Galton Professor of Eugenics at University College, London from 1945-63 (Professor of Human Genetics there from 1963-65), Lionel Penrose (1898-1972), father of the mathematician and theoretical physicist, Sir Roger Penrose (b.1931) does not say much for him or his methods. Measuring and comparing skulls was the sort of thing the Italian anthropologist Cesare Lombroso (1835-1909) did in order, so he claimed, to be able to identify the 'criminal type', that was - allegedly - a retrogression to a more 'primitive' form of humanity. It's also, of course, the sort of thing the Nazis did in order to identify the characteristics of supposed Untermenschen in comparison with the Aryan Master Race.

Before anyone springs to Dr Stringer's defence on the grounds that I have unfairly maligned him by comparing him with the Nazis, let it be noted that modern Australian Aboriginals and New Zealand Maoris have skull features bearing strong similarities to those of Neanderthals. Are they to be dismissed as 'primitive'? See: Nature, 2011; Lambers, Berner & Kremmler, 2022, pp.46, ff.

What paleoanthropologists seem almost desperate to avoid doing is to accept that Neanderthals and Denisovans were not separate species to ourselves, but merely distinct subspecies, which is why our ancestors were able to interbreed with them and produce fertile hybrid offspring, which accounts for the presence in modern nuclear genomes of Neanderthal and Denisovan DNA. They weren't mere hominins - they were human! They had language, culture and religion, probably of an animistic and/or shamanistic kind (van Binsbergen, 2018; Frayer, Radovčić, J. & D., 'Krapina and the Case for Neandertal Symbolic Behavior,' Current Anthropology, 61(6):713-731, December 2020, DOI: 10.1086/712088; Nielsen, et al, 2020); they had art; they buried their dead with ritual and ceremony, and grieved for them - but believed in an afterlife. They may well have used psychotropic plants or fungi to go on 'spirit journeys' to communicate with spirits, including the spirits of the dead, although this is speculative.

There is a final, and rather more depressing, point. These same paleoanthropologists seem very keen to deny, and conceal, the role our ancestors played in bringing about the demise of the Neanderthals, favouring almost any 'explanation' for their extinction bar the real one - which is that those ancestors of ours engaged in an act of genocide, and exterminated their close cousins, the Neanderthals and the Denisovans. That's what we do, you see - we get rid of the competition, just as John Wyndham argued in The Midwich Cuckoos (1957) and The Chrysalids (1955). Unlike the rather more sensible ten-spined stickleback, Pygosteus pungitius, we aren't willing to curb our reproductive activity when resources become scarce, but resort to employing inter-species, or even inter-subspecies, aggression, rather than (temporary) homosexual behaviour (see Morris, D., 'Homosexuality in the Ten-Spined Stickleback (Pygosteus pungitius L.),' Behaviour, 4(4):233-261, 1952).

Result? There are now over 8 billion of us on this planet - far more than it can sustain, and we have exterminated species after species of plants and animals to help us achieve that dubious end. Will we profit from our bloody triumph? NO - we will not, because Gaia will have her revenge!