The Caveman's Dental Records: What Fossil Teeth Tells Us About the Diets of Early Hominids, and What the Purpose of their Sometimes Impressive Fangs Might Be

• In many crime stories on television, and in the movies,   otherwise untraceable  corpses are often identified through the use of dental records. In most cases, it is done by having the police, a coroner, or members of the  crime scene team canvass area dentists. Most commonly the dentists examine an x-ray of the body’s jaw,  or on very rare occasions the jaws of the skull of a decomposed body themselves, and then search their memories and their records trying to match  the patterns of fillings, root canals, or missing teeth, and the size and shape of the jaw.

• The reasons for the use of teeth as an identification help is that they are surprisingly tough, much like the rest of the skull, and in particular, the jaw bones within which they reside in life. Experts in the fields of taphonomy (the study of the fossilization of the formerly living bone and tissues), forensic anthropologists and field archeologists attest to this through a prodigious output of papers in which the analysis of dental remains are involved. It is no surprise that many of the professors who teach gross anatomy at dental schools, publish in journals of anthropology and archeology.

• According to Anthropological Index there were at least 594 articles at the time of this blog  that deal with analyzing fossil  teeth alone. This is apart from  hundreds more studies that analyze human teeth from “modern” humans who have died over the  last 10,000 years, for reasons including archeology and criminal investigation.

• Among other things, we know the size of teeth and state of dentition in the Roman Empire  at the time of the eruption of Mt. Vesuvius was varied -----some Pompeians had teeth in great condition; others not so much. And we have learned conclusively that many Viking warriors  actually filed their teeth to a point to create a more fierce appearance.

• We have also learned a number of things about fossil hominid teeth over the course of evolution.  We have learned that Neanderthals had baby teeth pretty much like modern humans in that they were shed (and lucky for us, preserved….although one can only imagine the compound interest for a few hundred thousand years to be paid on the equivalent of a US quarter under the pillow (if they had pillows then!).

• Another point  is that our dental enamel has increased in thickness over the course of evolution, which helped our ancestor’s teeth better to withstand the wear. Tooth wear is of one of  the great talking points in physical anthropology because it is thought to be indicative of the diet of primitive man and of his place on the food chain.

• One of the greatest areas of debate in dental anthropology is whether or not jaw anatomy or dentition   is necessarily dietary destiny. In other words, if possible progenitors of humans or other modern primates had a particularly powerful jaw and robust teeth that looked like they were made for  eating hard foods, is this clearly indicative that they in fact, did eat a diet of particular tough food that essentially had to be ground, with the teeth acting as much like mortar and pestle?

• In a recent article in PLoS One (that is the Public Library of Science’s Open Access journal for any topic in science), the team of Peter Ungar of the University of Arkansas, Frederick Grimes who holds  trans-Atlantic positions at both Cambridge University in England and Stony Brook in New York,  and Mark Teaford of Johns Hopkins School of Medicine examine the case of the teeth and jaws of “Nutcracker Man. ” Nutcracker man is more formally known as Paranthropis boisei  and like many fossil hominids,  its discovery and early study involved the famed Leakey family. 

• Anthropologists have long been able to infer with exceptional reliability, a great deal about animal and hominid musculature, tendon placement, and the strength of the resulting functional unit, owing to indentions and grooves in bone structure. This is based on techniques that go back to the 19^th century comparative anatomists Cuvier of France and Owen of the UK. They tested their assumptions by making predictions of how the anatomy would piece together, and perform in a living creature, from reconstructing the disarticulated bones of animals that had been dissected and flensed (stripped of muscle) by others, and then by subsequently observing and sometimes actually testing the function and strength of still living animals like them, to see if their reconstructions made sense.

• A variant of this approach has been used for humans in the case of forensic facial reconstructions done from fleshless skulls through the computer-assisted clay remodeling of missing muscle, tendons and tissues. When photos of the deceased are finally retrieved after reconstruction, the likeness is often quite striking.

• Everything dentally anatomical  about Nutcracker Man, on first examination at least, suggested that he had precisely the right kind of the musculature, and the generally flattened “made-for-grinding”  teeth. They would clearly be   capable of cracking and pulverizing  nuts,  hard roots and tubers.  Nutcracker man apparently did so successfully enough to have lasted for a million years, because reliable means of dating the specimens that the team analyzed,  had demonstrated the Nutcracker Man fossils spanned at least that amount of earth history.

• But the team worked up a three part critique that suggested a new approach. The critique  consisted of:

• A hypothesis…

• An observation that might or might not be pertinent…

• And a famous conjecture  from a scholar  at Harvard’s Museum of Comparative Zoology, Karel Liem.

 

• The hypothesis was that gross examination of the teeth might not be enough to tell the whole story of what in fact Nutcracker Man ate, or ate most often, or ate at the time of his death...

• The observation that was that gorillas have very powerful jaws and teeth, but do not necessarily eat the food routinely that would require them to deploy all that potential. (All things considered, primatologists have long known that gorillas would rather eat ripe fruit.)

• The conjecture was closely related: Karel Liem’s conjecture states that just because an animal has an extraordinary anatomical feature, does not mean that this feature determined the course of it dietary life history, In other words, you can inherit the build of a linebacker and still end up eating like a librarian.  (My problem is that I am a librarian who eats like a linebacker, and has the build of a beach ball.)

• The team’s new approach was to scan the surface of the molars microscopically under high magnification with the ability to resolve 3-d features at very small scales,  to see if the fine details of the wear patterns were more consistent with the gross morphology: showing that the power of the anatomy was consistently put to the hardest work of which it was capable, or if it told another story.

• It told another story: it appears that the majority of specimens of Nutcracker Man, Paranthropis boisei, actually showed striations that indicated a far more fibrous and leafy diet. Liem’s conjecture seemed to hold sway.

• Yet another team featuring a professor from the University of Arkansas, this time, J. Michael Plavcan of the Department of Anthropology, and from Johns Hopkins School of Medicine,  this time, Christopher Ruff, have taken on a related issue: what can the sometimes very long “fangs” or canine teeth of some male primates tell us about their use, and in particular, given their extraordinary length, could  the fangs be easily broken off.

• The canine teeth of over 100 different primates which have preserved or fossilized specimens, were compared with canines of large carnivores (bears, tigers, wolves, hyenas, etc.).  Estimates were made of whether or not, pound for pound (actually comparable Body Mass Index to Body Mass Index) , the teeth of the primates were as proportionately large as those of these other presumed carnivores.

• They were, with one seemingly  important difference. After a point, carnivore canine teeth tend to grow somewhat less in height than in width at the base, which secures their canine teeth very strongly, whereas primate canine teeth stay fairly narrow at the base and grow proportionally longer. 

• The team then tested their breakability, using standard engineering stress formulas, on the theory that there might be increasing structural  weakness with increasing length, but this proved not to be the case. These canine teeth were indeed well-designed to stay in place, unbroken, despite considerable torque.

• The discussion then turned to the degree were these capable–of-meat-ripping teeth were put to work for that purpose. It turns out, not unlike the case with the earlier paper by their colleagues, not all that often for meat-eating. Indeed only three species within this extensive family of primates are known to hunt for flesh on a regular basis. More many species use the canines to crack nuts open!

• The question then remained, what were these very strong and very long teeth for? Three hypotheses remain. 

• First, the teeth may be use for defense against other carnivores, although that has not been generally observed.

• Second, the teeth  may be useful for combat for dominance among males of their own species, although the authors report that the evidence for this has not been convincing across the entire spectrum of primates with long canines, although many field studies have  disclosed canine teeth displaying, combats, woundings and occasional fatalities. Ironically,  female primates who have proportionately much smaller canines, also use them to assert female dominance, and gang up upon, and kill other unwanted or insubordinate females with them.

• Third, the teeth may be useful as sexual attractants for females of the species. (In this case, size in the sense of length, if not necessarily a wider base, might well matter.)

• This still begs the question of why the male’s canines  have to be so strong as to be unbreakable.  There are hundreds of pages of discussion in the  articles cited below on this. But perhaps the following analogy works better, and sooner, for at least one class of primates.

• Two guys ask a girl out.
• One has a prominent gap in his smile,  where a front tooth is clearly missing.
• The other guy has a  nice smile , with a complete set of teeth.
• Which do you think is going to, ahem, get the  chance to pass on genes for very long and particularly strong canine teeth?

Arcini, C.  2005.  The Vikings bare their filed teeth.  American Journal Of Physical Anthropology  128 (4 ): 727-733.

Bermúdez de Castro, J. M. &  M.E.  Nicolás. 1996.  Changes in the lower premolar-size sequence during the hominid evolution: phylogenetic implications. Human Evolution 11 (3-4): 205-215.

Christiensen, P. &  J.S. Adolfssen. 2005. Bite forces, canine strength and skull allometry in carnivores (Mammalia: Carnivora). Journal of Zoology 266: 133-151.

Coppa, A., F.  Manni,  C. Stringer,  et al.  2007. Evidence for new Neanderthal teeth in Tabun Cave (Israel) by the application of self-organizing maps (SOMs).  Journal Of Human Evolution 52 (6): 601-613. 

Dean, M. C. 1987. Growth  layers and incremental markings in hard tissues; a review of the literature and some preliminary observations about enamel structure in Paranthropus boisei.  Journal Of Human Evolution 16 (2): 157-172.

Dean, M. C.. &  A.D.  Beynon. 1991. Tooth crown heights, tooth wear, sexual dimorphism and jaw growth in hominoids.  Zeitschrift für Morphologie und Anthropologie 78 (3):  425-440. 

Demes, B. & N. Creel. 1988. Bite force, diet, and cranial morphology of fossil hominids. Journal of Human Evolution 17: 657-670.

Egocheaga, J.E.,  A. Pérez-Pérez, L. Rodríguez et al. 2004. New evidence and interpretation of subvertical grooves in Neanderthal teeth from Cueva de Sidrón (Spain) and Figueira Brava (Portugal)   Anthropologie : International Journal of the Science of Man   42 (1): 49-52.

Estebaranz, F., L. M. Martínez,  O. Hiraldo et al.  2004. Tooth crown size and dentine exposure in Australopithecus and early Homo : Testing hypothesis of dietary related selective pressures Source:     Anthropologie : International Journal of the Science of Man  42 (1): 59-63.   

Galbany, J., L.M.  Martínez,  & A. Pérez-Pérez, Alejandro. 2004. Tooth replication techniques, SEM imaging and mircowear analysis in primates : methodological obstacles. Anthropologie : International Journal of the Science of Man . 42 (1):5-12.

Gantt, D. G.  1983.  Enamel of neogene hominoids: structural and phyletic implications.  in New Interpretations Of Ape And Human Ancestry.  New York: Plenum Press. pp..249-298.

Gittelman, J.L. & B. Van Valkenburgh. 1997. Sexual dimorphism in the canines and skulls of carnivores: Effect of size, phylogeny and behavioral ecology. Journal of Zoology 242: 97-117.

Gómez-Robles, A.; M. Martinón-Torres,  J.M. Bermúdez  de Castro et al.  2007. A geometric morphometric analysis of hominid upper first molar shape. Journal of Human Evolution  53 (3):  272-285 . 

Greenfield, L.O. 1992. Origin of the human canine: A new solution to an old dilemma. Yearbook of Physical Anthropology 35: 153-185.

Greenfield, L. O.  1993. Tooth at the border of two morphogenetic fields. Human Evolution 8  (3):  187-204.

Greenfield, L.O. 1998. Canine tip wear in male and female anthropoids. American Journal of Physical Anthropology 107: 87-96.

Grine, F.  E.  1986. Dental evidence for dietary differences in Australopithecus and Paranthropus: A quantitative analysis of permanent molar microwear.  Journal Of Human Evolution 15 (8):783-822.

Grine, F.  E. 1989.  New hominid fossils from the Swartkrans formation (1979-1986 excavations): Craniodental specimens.     American Journal of Physical Anthropology  79 (4): 409-449. 

Harvati, K. &   S.R.  Frost, Stephen. 2007.   Dental eruption sequences in fossil Colobines and the evolution of primate life histories.  International Journal Of Primatology  28 (3): 705-728.   

Henneberg, M.,  R.J.  Henneberg,  & A. Ciarallo. 1996. Skeletal material from the house of C.  Iulius Polybius in Pompeii, 79 AD.  Human Evolution  11 (3-4): 249-259.   

Hylander, W.L. 1988. Implications of in vivo experiments for interpreting the functional significance of “robust” Australopithicine jaws. in  Grine, E. F. ,  ed. Evolutionary History of “Robust Australopithicines. New York: Aldine de Gruyter.  pp.55-83.

Jungers, W. L. &  F. E.  Grine.  1986. Dental trends in the Australopithecines: the allometry of mandibular molar dimensions. in   Major Topics In Primate And Human Evolution. Bernard Wood, Lawrence Martin, and Peter Andrews, eds. Cambridge, Eng. : Cambridge University Press, pp. 203-219.

Jungers, W.L.  & P.D.  Gingerich.  1980. Supernumerary molars in Anthropoidea, Adapidae, and Archaeolemur: implications for primate dental homologies. American Journal of Physical Anthropology.  52 (1):  1-5.

Kay, R.F. 1985. Dental evidence for the diet of Australopithecus. Annual Review Of Anthropology 14: 315-341.

Kay, R.F., J.M. Plavcan, K.E. Glander et al. 1988. Sexual selection and canine dimorphism in New World monkeys. American Journal of Physical Anthropology 77: 385-397.

Keith, A. &  G.E. Smith. 1932.  Oldoway teeth. Man 32: 248.

King, T., P. Andrews, and B. Boz. 1999. Effect of taphonomic processes on dental microwear. American Journal of Physical Anthropology 108: 359-373.

Koski, K., &  S. M.  Garn. 1957. Tooth eruption sequence in fossil and modern man. American Journal Of Physical Anthropology. 15: 469-488.

Laden, G. & R. Wrangham. 2005. The rise of the hominids as an adaptive shift in fallback foods: Plant underground storage  organs (USOs) and Australopith origins. Journal of Human Evolution 49: 482-498.

Leigh, S.R. & J.M. Setchell. 2006. Fitness and canine size in male mandrills (Mandrillus sphinx). American Journal of Physical Anthropology 42 (Supplement): 120.

Leutenegger, W. & J.T. Kelly. 1977. Relationship of sexual dimorphism in canine size and body size to social, behavioral and ecological correlates in anthropoid primates. Primates 18: 117-136.

Lucas, P.W. 2004. Dental Functional Morphology: How Teeth Work. New York: Cambridge University Press.

Lucas, P.W., R.T. Corlett, & D.A. Luke. 1986. Postcanine tooth size and diet in anthropoid primates. Zeitschrift fuer Morpholgie und Anthropologie 76: 253-276.

Lucas, P.W., R.T. Corlett & D.A. Luke. 1986. Sexual dimorphism in tooth size in anthropoids. Human Evolution 1: 23-39.

Manzi, G., E.  Santandrea  & P. Passarello. 1997. Dental size and shape in the Roman imperial age: Two examples from the area of Rome.  American Journal Of Physical Anthropology 102 (4): 469-479.

Martin, L. 1988. Paleoanthropology: Teeth, sex and species. Nature 352: 111-112.

McGraw, W.S., J.M. Plavcan, & K. Adachi-Kanazawa. 2002. Cercopithecus  diana employ canine teeth to kill another female C. diana . International Journal of Primatology 23: 1301-1308. 

McHenry, H. M. 1985. Implications of postcanine megadontia for the origin of Homo. 1985. In  Ancestors: The Hard Evidence. E.  Delson, ed.,  pp.178-183.

Menter, C. G., K.L.  Kuykendall, & A.W.  Keyser, et al. 1999. First record of hominid teeth from the Plio-Pleistocene site of Gondolin, South Africa. Journal Of Human Evolution 37 (2): 299-307. 

Nagatoshi, K. 1990.  Molar enamel thickens in European Miocene and extant Hominoidea. International Journal of Primatology  11 (4): 283-295. 

Plavcan, J.M. 1993. Canine size and shape in male anthropoid primates. American Journal of Physical Anthropology 92: 201-216.

Plavcan, J.M. Correlated response, competition, and female canine size in primates. American Journal of Physical Anthropology 107: 401-416.

Plavcan, J.M. 2001. Sexual dimorphism in primate evolution. Yearbook of Physical Anthropology  44:25-58.

Plavcan, J.M. 2003. Scaling relationships between craniofacial sexual dimorphism in primates: Implications for the fossil record. American Journal of Physical Anthropology 120: 38-60.

Plavcan, J.M. & C.P. van Schaik. 1992. Intrasexual competition in and canine dimorphism in anthropoid primates. American Journal of Physical Anthropology 87: 461-477.

Plavcan, J.M. & C.P. van Schaik. 1994. Canine dimorphism. Evolutionary Anthropology  2: 208-214.

Plavcan, J.M., C.P. van Schaik & P.M. Kappeler. 1995. Competition, coalitions, and canine size in primates. Journal of Human Evolution 28: 245-276.

Plavcan, J.M. & C.B. Ruff. 2008. Canine Size, Shape, and Bending Strength in Primates and Carnivores. American Journal of Physical Anthropology 136; 65-84.

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Scott, R.S., P.S. Ungar, T.S. Bergstrom et al. 2005. Dental microwear reflects diets of living primates and fossil hominids. Nature 436: 693-695.

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Simpson, S. W.; R. S. Meindl,  & C.O. Lovejoy. 1990.  Hominoid dental maturation.  Journal Of Human Evolution  19 (3): 285-297. 

Smith, P. 1977.   Selective pressures and dental evolution in hominids. American Journal Of Physical Anthropology 47 ( 3): 453-458.

Spencer, M. A. &  P.S.  Ungar. 2000.  Craniofacial morphology, diet and incisor use in three Native American populations. International Journal of Osteoarchaeology  10 (4): 229-241. 

Smith, R.J. 1981. Interspecific scaling of maxillary canine size and shape in female primates: Relationships to social structure.  Journal of Human Evolution 10: 165-173.

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Teaford, M.F. 1988. Scnning electron microscope diagnosis of wear patterns versus artifacts on fossil teeth. Scanning Microscopy 2: 1167-1175.

Teaford, M.F. & A. Walker. 1984. Quantitative differences in dental microwear between primate species with different diets and a comment on the presumed diet of Sivapithecus. American Journal of Physical Anthropology 64: 191-200.

Teaford, M.F. & O.J. Oyen. 1989. In vivo and in vitro turnover in dental microwear. American Journal of Physical Anthropology 80: 447-460.

Teaford, M.S. & P.S. Ungar. 2000. Diet and the evolution of the earliest human ancestors. Proceedings of the National Academy of Sciences 97: 13506-13511.

Teschler-Nicola,  M., W.  Antl-Weiser,  & H. Prossinger.  2004. Two Gravettian human deciduous teeth from Grub/Kranawetberg, lower Austria .  Homo  54 (3): 229-239.   

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Tobias, P. V. 1987. On  the relative frequencies of hominid maxillary and mandibular teeth and jaws as taphonomic indicators. Human Evolution  2 (4): 297-309.

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Ungar, P.S., C.A. Brown, T.S. Bergstrom, et al. 2003. Quantification of dental microwear by tandem scanning confocal microscopy and scale-sensitive fractal analysis. Scanning 25: 185-193.

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Tony Stankus, tstankus@uark.edu 

Life Sciences Librarian & Professor

University of Arkansas Libraries MULN 223E

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