Neanderthals are us?

May 15, 2011 • 9:03 pm

by Greg Mayer

At least since Socrates explored the meaning of the Greek maxim “Know thyself”, and Alexander Pope added that “the proper study of Mankind is Man”, we have been interested in knowledge about ourselves. But who are we? A paper in press in the Proceedings of the National Academy of Sciences by Ron Pinhasi and colleagues raises this issue with regard to Neanderthals, an issue which Jerry considered a while back: are they us?

In several senses, they obviously are us: fellow mammals, fellow primates, fellow hominids, and fellow members of the genus Homo, and thus men in the generic sense (in both the vernacular and technical senses of generic). But are they members of the same species as us, Homo sapiens? Or members of a distinct species, Homo neanderthalensis?

Life reconstruction of a Neanderthal by John Gurche at the USNM.

The question of whether they are a different species from us is the question of whether or not we could interbreed with each other. And not just mate– but successfully produce fertile offspring. For most of the time since the first reported Neanderthal in 1856, reproductive compatibility could only be inferred based on morphological data, and opinions varied as to whether Neanderthals were a subspecies of H. sapiens or a separate species. The great Finnish paleontologist Bjorn Kurten proposed in his novel, Dance of the Tiger, that Neanderthals and modern H. sapiens could mate and produce offspring, but that the offspring, while showing somatic luxuriance (they were really smart and strong), were completely sterile (a form of post-mating reproductive isolation). Published in 1980 before there was any genetic evidence, a novel, rather than a scientific paper, was probably the right venue for Kurten’s reasoned but entirely speculative proposal.

Early genetic data from mitochondrial DNA indicated that Neanderthal mitochondria were well outside the variability of modern populations, supporting the ideas of those (such as Kurten) who supposed that Neanderthals were a separate species. More recently obtained nuclear DNA sequences, however, showed that 1-4% of the genome of modern Eurasians was derived from Neanderthals (modern Africans lack this admixture of Neanderthal DNA). Thus there was enough successful interbreeding to leave a noticeable signature in modern genomes. Even more recently, a previously unknown fossil Asian population called Denisovans, related to but distinct from Neanderthals, has been shown to have contributed about 5% of the genome of modern Melanesians. Thus, measurable interbreeding occurred between anatomically modern humans and more archaic Eurasian populations as the former spread out of Africa across the remainder of the Old World.

The paper by Pinhasi et al. revises the dating of Neanderthal fossils from the Caucasus, finding them to be older than previously thought (about 40,000 years BP). The authors also suggest that other younger dates are unreliable, and that it is unlikely that anatomically modern humans and Neanderthals coexisted for any substantial length of time. If they are correct, then the Neanderthal (and Denisovan) contribution to modern genomes speaks even more strongly of conspecficity, as the gene flow had to occur over shorter periods of time. There are, regrettably, quite a few historical instances where two peoples (both of course undoubted anatomically modern H. sapiens) met, and one quickly disappeared, with relatively little measurable gene flow having occurred, so the rapid demise of Neanderthals in the face of anatomically modern humans is no bar to their having been the same species. I would interpret the genetic evidence so far as indicating that the Neanderthals, indeed, are us.

In addition to the references below, John Hawks of the University of Wisconsin, Madison, has a fine blog in which he often comments on Neanderthals and other paleoanthropological topics. His take on the Pinhasi et al. paper, which deals more with the dating issues, is here; his view on the species question is here. [JAC: I also discussed the species problem in Neanderthals, reaching the same conclusion as Hawks.]


Green, R.E. et al. 2010. A draft sequence of the Neandertal genome. Science 328:710-722.

Green, R.E., et al. 2008. A complete Neandertal mitochondrial genome sequence determined by high-throughput sequencing. Cell 134:416-426.

Kurten, B. 1980. Dance of the Tiger. Reissued by University of California Press, Berkeley, 1993.

Pinhasi, R., T.F.G. Highamb, L.V. Golovanovac, and V.B. Doronichev. 2011 Revised age of late Neanderthal occupation and the end of the Middle Paleolithic in the northern Caucasus. Proceedings of the National Academy of Sciences in press.

Reich, D., et al. 2010. Genetic history of an archaic hominin group from Denisova Cave in Siberia. Nature 468:1053-1060.

Clouded leopards and the species problem

January 25, 2011 • 10:48 am

by Greg Mayer

Alert WEIT-blog reader Dominic has drawn my attention to a not yet published study of clouded leopards, that I’d seen mentioned by the BBC, but I had not seen the actual paper (well, actually, nobody has seen the actual paper— more below on this).

Clouded leopard by Vearl Brown, from Wikipedia.

There are two issues here, both of which we’ve considered before here at WEIT. First is the species concept issue, which both Jerry and I mentioned recently (links to Jerry’s posts in mine). The second is a scientific nomenclature issue, one that arose in the infamous Darwinius case.

The species concept issue also comes in two parts. First, are the mainland clouded leopard (Neofelis nebulosa) and the insular clouded leopard (Neofelis diardi) distinct species? And, second, among the insular clouded leopards, are the Bornean and Sumatran populations distinct? The first issue was the focus of two papers in 2006 which raised the insular leopards to full species status. Normally, the raising of insular forms to full species status on the basis of being different from the mainland form raises a warning flag for me, but there is an additional consideration which I think in this case supports the raising to full species status. This is that the islands of Borneo and Sumatra are on the Sunda Shelf, and thus were connected to the mainland as recently as about 10,000 years ago (see Harold Voris’s superb series of paleo-bathymetric maps of the Sunda Shelf for details). So, the insular and mainland forms were in contact very recently, and one good explanation for why this contact would not have led to an erosion of the genetic differences between them is that they were reproductively isolated (i.e., different species). There are other possible interpretations, but the recent contact combined with observed differences certainly makes the 2-species taxonomy reasonable.

The new, unpublished, paper argues not for a new species, but for dividing the insular form into two subspecies, one from Borneo and one from Sumatra. (A subspecies is recognized when there is a particular pattern of geographic variation within a species, namely that there is a geographic segment of the species’ range within which individuals can be distinguished from individuals from other parts of the range. Basically, if you can tell where an individual is from by the way it looks, or, if you tell me where the individual is from, I can tell you what it looks like, then you can name a subspecies.) This seems perfectly reasonable to me.

The problem is that they describe a new subspecies in the paper (rather than reviving a previously described one), but they have also posted a pre-print online and allowed press coverage. Online posting does not constitute publication in the formal sense, and their paper will soon be published on paper. But by generating press coverage (the BBC has included the new name in its coverage) and posting online, they increase the chance that the name will be formally published before their paper appears in print, either accidentally, or on purpose by an unscrupulous individual wanting to steal credit for their work (it does happen). This was part of the problem with Darwinius: the name Darwinius was bandied about before the name was published.

The authors are actually compounding a problem they created for themselves earlier: they published the new name in 2007 (I have not seen this paper), but now consider their proposal at the time nomenclaturally defective, and the name not nomenclaturally available from that publication. (The technical term for what they now regard their 2007 effort is a nomen nudum: a nude name, i.e. a name without a proper description accompanying it, and thus not available for use as a scientific name). The nomenclature of this name could be confused. I hope their paper appears soon.

One thing highlighted by this paper that I want to unreservedly endorse is the use of camera traps for the study of elusive large mammals. These traps have helped with studies of a number of species, including several big cats: jaguars (including Arizona jaguars), Saharan cheetahs, Asiatic cheetahs, tigers, as well as clouded leopards. The BBC, NYT, and other media often highlight the results of these studies. Recently, camera traps revealed an unexpected high-altitude population of tigers in Bhutan, in a valley where three big cats– leopard, snow leopard, and tiger– all live together.

Buckley-Beason, V.A. et al. 2006. Molecular evidence for species-level distinctions in clouded leopards. Current Biology 16:2371-2376. (pdf)

Kitchener, A.C., M.A. Beaumont, and D. Richardson. 2006. Geographical variation in the clouded leopard, Neofelis nebulosa, reveals two species. Current Biology 16:2377-2383. (pdf)

Wilting, A., V.A. Buckley-Beason, H. Feldhaar, J. Gadau,  S.J. O’Brien, and K.E. Linsenmair. 2007. Clouded leopard phylogeny revisited: support for species recognition and population division between Borneo and Sumatra. Front. Zool. 4:15. (not seen)

Wilting, A., P. Christiansen, A.C. Kitchener, Y.J.M. Kemp, L. Ambu, and J.Fickel. 2011. Geographical variation in and evolutionary history of the Sunda clouded leopard (Neofelis diardi) (Mammalia: Carnivora: Felidae) with the description of a new subspecies from Borneo. Molecular Phylogenetics and Evolution in press. (pdf)