A geometric morphometric re-evaluation of the use of dental form to explore differences in horse (Equus caballus) populations and its potential zooarchaeological application

Krish Seetah, Thomas Cucchi*, Keith Dobney, Graeme Barker

*Corresponding author for this work

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The domestication of the horse specifically its use as a transport animal had a unique impact on the evolution of human societies. Along with its influence on warfare, the horse transformed land transportation, radically altering the distance that humans could travel in a day, week, month or lifetime. Over the last century horse domestication has been investigated by zooarchaeologists using morphometric, morphological and (more recently) biomolecular approaches in attempts to identify distinct 'domestic' phenotypes in the fossil record. However, identification of domestic morphotypes have been complicated by the low variation in equid cranial morphology and apparent limited changes brought about through the domestication process compared with other domestic taxa. Furthermore, cranial morphology is too prone to ecophenotypic plasticity to provide relevant taxonomic markers. Even dental morphology (of primary importance for taxonomic investigation in the fossil record) has been dismissed as a useful marker for horse domestication, since variations in tooth size and enamel patterns are considered to be too greatly influenced by age and continuous tooth wear. The proof-of-concept study presented here re-evaluates the potential of cheek teeth shape to capture significant differences between horse populations. Using geometric morphometrics (GMM), we study the enamel-folding pattern of the upper P-2 and M-3, selected for their distinctive morphology amongst the cheek teeth. Curated specimens of known age and sex from two horse (Equus caballus) breeds Icelandic and Thoroughbred were used to investigate whether the effects of age (through occlusal wear), sexual dimorphism and allometry (size-related change in shape) should be regarded as confounding factors preventing any accurate discrimination between these two populations. The results show that a landmark based approach applied to the occlusal enamel folding of the P-2 and M-3 captures significant differences in size (centroid) and shape between the horses breeds studied. Age-related factors, allometric scaling and sexual dimorphism are not confounding factors in their discrimination, encouraging the use of dental form in population-based research on ancient horse remains. (C) 2013 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)904-910
Number of pages7
JournalJournal of Archaeological Science
Volume41
Early online date31 Oct 2013
DOIs
Publication statusPublished - Jan 2014

Keywords

  • Equus caballus
  • population discrimination
  • teeth
  • age effect
  • sexual dimorphism
  • zooarchaeology
  • pig domestication
  • mitochondrial-DNA
  • fossil horses
  • ancient DNA
  • shape
  • insights
  • origins
  • dispersal
  • mammals
  • China

Cite this

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title = "A geometric morphometric re-evaluation of the use of dental form to explore differences in horse (Equus caballus) populations and its potential zooarchaeological application",
abstract = "The domestication of the horse specifically its use as a transport animal had a unique impact on the evolution of human societies. Along with its influence on warfare, the horse transformed land transportation, radically altering the distance that humans could travel in a day, week, month or lifetime. Over the last century horse domestication has been investigated by zooarchaeologists using morphometric, morphological and (more recently) biomolecular approaches in attempts to identify distinct 'domestic' phenotypes in the fossil record. However, identification of domestic morphotypes have been complicated by the low variation in equid cranial morphology and apparent limited changes brought about through the domestication process compared with other domestic taxa. Furthermore, cranial morphology is too prone to ecophenotypic plasticity to provide relevant taxonomic markers. Even dental morphology (of primary importance for taxonomic investigation in the fossil record) has been dismissed as a useful marker for horse domestication, since variations in tooth size and enamel patterns are considered to be too greatly influenced by age and continuous tooth wear. The proof-of-concept study presented here re-evaluates the potential of cheek teeth shape to capture significant differences between horse populations. Using geometric morphometrics (GMM), we study the enamel-folding pattern of the upper P-2 and M-3, selected for their distinctive morphology amongst the cheek teeth. Curated specimens of known age and sex from two horse (Equus caballus) breeds Icelandic and Thoroughbred were used to investigate whether the effects of age (through occlusal wear), sexual dimorphism and allometry (size-related change in shape) should be regarded as confounding factors preventing any accurate discrimination between these two populations. The results show that a landmark based approach applied to the occlusal enamel folding of the P-2 and M-3 captures significant differences in size (centroid) and shape between the horses breeds studied. Age-related factors, allometric scaling and sexual dimorphism are not confounding factors in their discrimination, encouraging the use of dental form in population-based research on ancient horse remains. (C) 2013 Elsevier Ltd. All rights reserved.",
keywords = "Equus caballus, population discrimination, teeth, age effect, sexual dimorphism, zooarchaeology, pig domestication, mitochondrial-DNA, fossil horses, ancient DNA, shape, insights, origins, dispersal , mammals, China",
author = "Krish Seetah and Thomas Cucchi and Keith Dobney and Graeme Barker",
note = "Acknowledgements This project was funded by the Leverhulme Trust (F/09 757/B), with additional support from the McDonald Institute for Archaeological Research, University of Cambridge. The authors would also like to thank Frieder Mayer (ZMB, Berlin) and Richard Sabin and Louise Tomsett (NHM, London) for the access respectively to the ICL and TB horse skeletal collections. We are extremely grateful to the three anonymous reviewers whose criticisms and comments have helped us improve the quality of the manuscript.",
year = "2014",
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language = "English",
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pages = "904--910",
journal = "Journal of Archaeological Science",
issn = "0305-4403",
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T1 - A geometric morphometric re-evaluation of the use of dental form to explore differences in horse (Equus caballus) populations and its potential zooarchaeological application

AU - Seetah, Krish

AU - Cucchi, Thomas

AU - Dobney, Keith

AU - Barker, Graeme

N1 - Acknowledgements This project was funded by the Leverhulme Trust (F/09 757/B), with additional support from the McDonald Institute for Archaeological Research, University of Cambridge. The authors would also like to thank Frieder Mayer (ZMB, Berlin) and Richard Sabin and Louise Tomsett (NHM, London) for the access respectively to the ICL and TB horse skeletal collections. We are extremely grateful to the three anonymous reviewers whose criticisms and comments have helped us improve the quality of the manuscript.

PY - 2014/1

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N2 - The domestication of the horse specifically its use as a transport animal had a unique impact on the evolution of human societies. Along with its influence on warfare, the horse transformed land transportation, radically altering the distance that humans could travel in a day, week, month or lifetime. Over the last century horse domestication has been investigated by zooarchaeologists using morphometric, morphological and (more recently) biomolecular approaches in attempts to identify distinct 'domestic' phenotypes in the fossil record. However, identification of domestic morphotypes have been complicated by the low variation in equid cranial morphology and apparent limited changes brought about through the domestication process compared with other domestic taxa. Furthermore, cranial morphology is too prone to ecophenotypic plasticity to provide relevant taxonomic markers. Even dental morphology (of primary importance for taxonomic investigation in the fossil record) has been dismissed as a useful marker for horse domestication, since variations in tooth size and enamel patterns are considered to be too greatly influenced by age and continuous tooth wear. The proof-of-concept study presented here re-evaluates the potential of cheek teeth shape to capture significant differences between horse populations. Using geometric morphometrics (GMM), we study the enamel-folding pattern of the upper P-2 and M-3, selected for their distinctive morphology amongst the cheek teeth. Curated specimens of known age and sex from two horse (Equus caballus) breeds Icelandic and Thoroughbred were used to investigate whether the effects of age (through occlusal wear), sexual dimorphism and allometry (size-related change in shape) should be regarded as confounding factors preventing any accurate discrimination between these two populations. The results show that a landmark based approach applied to the occlusal enamel folding of the P-2 and M-3 captures significant differences in size (centroid) and shape between the horses breeds studied. Age-related factors, allometric scaling and sexual dimorphism are not confounding factors in their discrimination, encouraging the use of dental form in population-based research on ancient horse remains. (C) 2013 Elsevier Ltd. All rights reserved.

AB - The domestication of the horse specifically its use as a transport animal had a unique impact on the evolution of human societies. Along with its influence on warfare, the horse transformed land transportation, radically altering the distance that humans could travel in a day, week, month or lifetime. Over the last century horse domestication has been investigated by zooarchaeologists using morphometric, morphological and (more recently) biomolecular approaches in attempts to identify distinct 'domestic' phenotypes in the fossil record. However, identification of domestic morphotypes have been complicated by the low variation in equid cranial morphology and apparent limited changes brought about through the domestication process compared with other domestic taxa. Furthermore, cranial morphology is too prone to ecophenotypic plasticity to provide relevant taxonomic markers. Even dental morphology (of primary importance for taxonomic investigation in the fossil record) has been dismissed as a useful marker for horse domestication, since variations in tooth size and enamel patterns are considered to be too greatly influenced by age and continuous tooth wear. The proof-of-concept study presented here re-evaluates the potential of cheek teeth shape to capture significant differences between horse populations. Using geometric morphometrics (GMM), we study the enamel-folding pattern of the upper P-2 and M-3, selected for their distinctive morphology amongst the cheek teeth. Curated specimens of known age and sex from two horse (Equus caballus) breeds Icelandic and Thoroughbred were used to investigate whether the effects of age (through occlusal wear), sexual dimorphism and allometry (size-related change in shape) should be regarded as confounding factors preventing any accurate discrimination between these two populations. The results show that a landmark based approach applied to the occlusal enamel folding of the P-2 and M-3 captures significant differences in size (centroid) and shape between the horses breeds studied. Age-related factors, allometric scaling and sexual dimorphism are not confounding factors in their discrimination, encouraging the use of dental form in population-based research on ancient horse remains. (C) 2013 Elsevier Ltd. All rights reserved.

KW - Equus caballus

KW - population discrimination

KW - teeth

KW - age effect

KW - sexual dimorphism

KW - zooarchaeology

KW - pig domestication

KW - mitochondrial-DNA

KW - fossil horses

KW - ancient DNA

KW - shape

KW - insights

KW - origins

KW - dispersal

KW - mammals

KW - China

U2 - 10.1016/j.jas.2013.10.022

DO - 10.1016/j.jas.2013.10.022

M3 - Article

VL - 41

SP - 904

EP - 910

JO - Journal of Archaeological Science

JF - Journal of Archaeological Science

SN - 0305-4403

ER -