Thursday, March 09, 2006

The late survival of Homotherium confirmed, and the Piltdown cats

Some of the most fascinating, illuminating insights into extinct animals come from data recorded by the people who saw them. We might be sad that the Pleistocene megafauna are gone, but at least our ancestors painted, carved and sculpted representations of them. I promised in a previous post that I'd add my 'Piltdown cats' text. Here it is: it's not news - in fact the main scoop here is now well known, but in the interests of recycling old text for a new audience, I thought I may as well post it. Incidentally, I used the term 'Piltdown cat' before Chris Moiser noted the journalistic employment of the term 'Piltdown puss' in his recent book, but that's another story.

In 1896, in the French cave of Isturitz, a 16-cm long statuette of a big cat was discovered. Initially interpreted as a representation of a cave lion, it was reinterpreted by Vratislav Mazak (1970) as more likely being a depiction of the sabre-tooth Homotherium latidens (a species sometimes dubbed the scimitar cat). Like a homothere, but unlike a lion, the statuette (which has since been lost) has a short tail and a deepened lower jaw. If the statuette is meant to depict Homotherium, it provides us with some new information on the life appearance of this cat, as it appears to be decorated with small spots, and to have a pale underside. As Rousseau (1971a, 1971b) described, there are also other Palaeolithic pieces of cave art that appear to depict homotheres.

The problem though is that the Isturitz statuette (and other pieces of evidence) is somewhere around 30,000 years old, and the last accepted datum for skeletal material of Homotherium in Europe is 300,000 years BP (Adam 1961) [though see below]. This significant discrepancy therefore suggests that Homotherium survived in Europe for much later than thought but, given that this has until now been based on artwork, the area has remained controversial. As Shuker (1989) wrote: ‘Were the above works of Palaeolithic art nothing more than inaccurate or idealized depictions of cave lions, or do they comprise genuine proof that the extraordinary scimitar cat was a contemporary of our ancestors for a far longer period of time than hitherto believed?’.

A new young homothere record

In March 2000 the fishing vessel UK33 trawled a partial felid lower jaw from an area SE of the Brown Bank in the North Sea, an area previously known for yielding Pleistocene and Holocene fossil mammals. As described by Jelle Reumer et al. (2003), the jaw is from a Homotherium latidens, and what is especially significant is that radiocarbon analysis dates it to 28,000 years BP. As Reumer et al. note, this is about the same age as the Isturitz statuette and therefore confirms the long-suspected late survival of this felid in Europe.

Incidentally, the climate in northern Europe at this time would have been quite harsh - the Devensian Glaciation was at its height between 25,000 and 15,000 years BP, and at this time northern Britain as far south as Yorkshire was covered by an ice sheet. Cold tundra and steppe environments occurred to the south and east of this ice sheet, and only cold-tolerant species could have lived in the area now occupied by the North Sea. Reindeer were living in Cambridgeshire, Polar bears in London, and Musk ox in Wiltshire. Homotherium latidens must also have therefore been a cold-tolerant species. Given that Homotherium species also dwelt in temperate and tropical environments (in Asia homotheres are known as far south as Java), this was clearly a highly adaptable felid.

The Piltdown cats

Prior to Reumer et al.’s discovery there were a number of British homothere fossils which were initially regarded as coming from late glacial deposits, and thus being somewhere around 13,000-11,000 years BP in age (i.e., as young as the youngest possible age for the youngest American material). Most famously they include a single canine from Robin Hood Cave, the largest cave of the Creswell Crag complex at Derbyshire, discovered in 1876. Describing the tooth in 1877, William Boyd Dawkins, the pioneering geologist and expert on Palaeolithic man, suggested that it may have been introduced into the cave by humans, as it appeared to bear both the marks of a flint tool, and an incomplete perforation at its base. On balance though, Dawkins concluded that the tooth suggested late survival of Homotherium in Britain. This idea has been mentioned by other workers and it led Kurtén (1968) to suggest that H. latidens survived in Britain for far longer than it did in mainland Europe, or in other words that Britain acted as a refugium for this disappearing species. Pleistocene refugia? Hang on: didn’t I talk about those in the previous blog?

Although it may have been separated from mainland Europe during one or more of the Pleistocene interglacials (namely during part of the Ipswichian Interglacial, between c. 130,000-70,000 years BP), the English Channel did not flood until c. 9000 years BP, so any homothere living in Britain between 13,000 and 11,000 years ago could still have walked to mainland Europe (Stuart 1974, Yalden 1982).

It is of further interest to note that, had a hypothetical homothere population become isolated in interglacial Britain, it may only have lasted for about 1000 years before become extinct due to inbreeding. Recent modelling work on population viability in large Pleistocene carnivorans (O'Regan et al. 2002) has shown that even glacial refugia the size of the Iberian and Italian peninsulas were not big enough for large felids to survive in when these populations became isolated, as they apparently did during the Pleistocene glaciations (though see previous blog, and I have more on this subject to add soon). Lack of space during these times may therefore have promoted extinction, an issue that is particularly poignant today as large carnivorans find themselves restricted to increasingly smaller islands of suitable habitat.

Returning to the Robin Hood Cave tooth, recent work indicates that Dawkins' initial suspicions were right. The fact that the tooth had been altered by humans indicates that it probably was traded and carried around by them long after its original owner had died (Charles & Jacobi 1994). Furthemore, the specimen was apparently discovered on one of the four days on which the senior archaeologist in charge of the site - Tom Heath - was absent. Consequently it is not surprising that hoaxing has been suggested at various times, and Yalden (1999) compared the Robin Hood Cave homothere to the Piltdown fossils (which I'll also be blogging on at some stage, due to mostly over-looked links with the world of British dinosaurs). This remains an unproven assertion however, and Kenneth Oakley's (1980) discovery that the tooth differs in its fluorine, uranium and nitrogen content from all other British homothere fossils has been used as evidence both for and against its being a hoax. Given these problems though it has been recommended that this record be ignored.

British homotheres are also known from the early Pleistocene site of Dove Holes near Buxton, Derbyshire, a site that also yielded giant hyaenas, straight-tusked elephants and southern mammoths (Dawkins 1903), but is today occupied by a municipal rubbish dump (Yalden 1999). Middle Pleistocene British homotheres are known from the cavern infill site near Westbury-sub-Mendip, Somerset (Bishop 1982). Finally, the Kent’s Cavern teeth - initially thought to be late Pleistocene - come from a cave that also contains older Pleistocene fossils, and it is now thought that they are also middle Pleistocene.

The figure of the Isturitz statue reproduced above is taken from Michel Raynal’s website….

Refs - -

Adam, K. D. 1961. Die Bedeutung der pleistozanen Saugetier-Faunen Mitteleuropas fur die Geschichte des Eiszeitalters. Stuttgarter Beitrage zur Naturkunde 78, 1-34.

Bishop, M. J. 1982. The mammal fauna of the early Middle Pleistocene cavern infill site of Westbury-sub-Mendip Somerset. Special Papers in Palaeontology 28, 1-108.

Charles, R. & Jacobi, R. M. 1994. The Lateglacial fauna from Robin Hood Cave, Cresswell: a re-assessment. Oxford Journal of Archaeology 13, 1-32.

Dawkins, W. B. 1903. On the discovery of an ossiferous cavern of Pliocene age at Dove Holes, Buxton (Derbyshire). Quarterly Journal of the Geological Society, London 59, 105-133.

Kurtén, B. 1968. Pleistocene Mammals of Europe. Weidenfeld & Nicolson (London).

Mazak, V. 1970. On a supposed prehistoric representation of the Pleistocene scimitar cat, Homotherium Farbrini, 1890 (Mammalia; Machairodontinae). Zeitschrift fur Saugertierkunde 35, 359-362.

Oakley, K. 1980. Relative dating of the fossil hominids of Europe. Bulletin of the British Museum (Natural History), Geology 34, 1-63.

O'Regan, H. J., Turner, A. & Wilkinson, D. M. 2002. European Quaternary refugia: a factor in large carnivore extinction? Journal of Quaternary Science 17, 789-795.

Reumer, J. W. F., Rook, L., Van Der Borg, K., Post, K., Mol, D. & De Vos, J. 2003. Late Pleistocene survival of the saber-toothed cat Homotherium in northwestern Europe. Journal of Vertebrate Paleontology 23, 260-262.

Rousseau, M. 1971a. Un félin à canine-poignard dans l’art paléolithique? Archéologia 40, 81-82.

Rousseau, M. 1971b. Un machairodonte dans l’art aurignacien? Mammalia 35, 648-657.

Shuker, K. P. N. 1989. Mystery Cats of the World. Robert Hale (London).

Stuart, A. J. 1974. Pleistocene history of the British vertebrate fauna. Biological Reviews 49, 225-266.

Yalden, D. W. 1982. When did the mammal fauna of the British Isles arrive? Mammal Review 12, 1-57.

Yalden, D. W. 1999. The History of British Mammals. Poyster Natural History (London).


Blogger Darren Naish said...

Jaime. It's good to be sceptical, but in this case your scepticism is unwarranted.

8:23 PM  

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