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PLoS biology2005; 3(8); e241; doi: 10.1371/journal.pbio.0030241

Evolution, systematics, and phylogeography of pleistocene horses in the new world: a molecular perspective.

Abstract: The rich fossil record of horses has made them a classic example of evolutionary processes. However, while the overall picture of equid evolution is well known, the details are surprisingly poorly understood, especially for the later Pliocene and Pleistocene, c. 3 million to 0.01 million years (Ma) ago, and nowhere more so than in the Americas. There is no consensus on the number of equid species or even the number of lineages that existed in these continents. Likewise, the origin of the endemic South American genus Hippidion is unresolved, as is the phylogenetic position of the "stilt-legged" horses of North America. Using ancient DNA sequences, we show that, in contrast to current models based on morphology and a recent genetic study, Hippidion was phylogenetically close to the caballine (true) horses, with origins considerably more recent than the currently accepted date of c. 10 Ma. Furthermore, we show that stilt-legged horses, commonly regarded as Old World migrants related to the hemionid asses of Asia, were in fact an endemic North American lineage. Finally, our data suggest that there were fewer horse species in late Pleistocene North America than have been named on morphological grounds. Both caballine and stilt-legged lineages may each have comprised a single, wide-ranging species.
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Publication Date: 2005-06-28 PubMed ID: 15974804PubMed Central: PMC1159165DOI: 10.1371/journal.pbio.0030241Google Scholar: Lookup
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  • Journal Article
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  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article discusses the evolution, classification, and geographic distribution of horses during the Pleistocene era (approximately 3 million to 0.01 million years ago) based on molecular evidence, suggesting that some species may have originated more recently than previously thought and others might in fact be native North American species, not introduced as previously believed.

Overview

This research study examines the fossil record of horses and attempts to clarify some points of confusion regarding the evolution and diversity of horses during the late Pliocene and Pleistocene eras. This period, which spans from around 3 million to 0.01 million years ago, is poorly understood, and the study aims to shed light on it by analyzing DNA sequences from ancient horse fossils.

Nature of Confusion in Understanding Equid Evolution

  • There are disagreements regarding the number of equid (horse) species and lineages that existed during the Pleistocene era, most notably in the Americas.
  • It has been difficult to resolve the origin of the South American genus Hippidion, a now-extinct genus of horses.
  • The ‘stilt-legged’ horses of North America, so named because of their long, slender legs, also pose a complicated problem as their phylogenetic (evolutionary development and diversification) position is unclear.

Key Findings of the Research

  • Contrary to current theories based on morphology (physical characteristics) and a recent genetic study, the researchers found that Hippidion was closely related to caballine (true) horses. The origins of Hippidion are also likely to be more recent than the generally accepted date of 10 million years ago.
  • Stilt-legged horses, previously considered to have originated from Asia and related to the hemionid asses of Asia, were found to be an endemic North American lineage, meaning they evolved independently in North America.
  • Based on the researchers’ data, there were likely fewer horse species in late Pleistocene North America than has been assumed based on morphological evidence, suggesting that both caballine and stilt-legged horses could each represent a single, wide-ranging species rather than multiple, distinct species.

Cite This Article

APA
Weinstock J, Willerslev E, Sher A, Tong W, Ho SY, Rubenstein D, Storer J, Burns J, Martin L, Bravi C, Prieto A, Froese D, Scott E, Xulong L, Cooper A. (2005). Evolution, systematics, and phylogeography of pleistocene horses in the new world: a molecular perspective. PLoS Biol, 3(8), e241. https://doi.org/10.1371/journal.pbio.0030241

Publication

PLoS biology
ISSN: 1545-7885
NlmUniqueID: 101183755
Country: United States
Language: English
Volume: 3
Issue: 8
Pages: e241
PII: e241

Researcher Affiliations

Weinstock, Jaco
  • Ancient Biomolecules Centre, Department of Zoology, University of Oxford, United Kingdom. jacobo.weinstock@zoo.ox.ac.uk
Willerslev, Eske
    Sher, Andrei
      Tong, Wenfei
        Ho, Simon Y W
          Rubenstein, Dan
            Storer, John
              Burns, James
                Martin, Larry
                  Bravi, Claudio
                    Prieto, Alfredo
                      Froese, Duane
                        Scott, Eric
                          Xulong, Lai
                            Cooper, Alan

                              MeSH Terms

                              • Animals
                              • Base Sequence
                              • Bone and Bones / anatomy & histology
                              • DNA, Mitochondrial / genetics
                              • Equidae / classification
                              • Equidae / genetics
                              • Evolution, Molecular
                              • Fossils
                              • Horses / classification
                              • Horses / genetics
                              • Molecular Sequence Data
                              • North America
                              • Phylogeny
                              • Sequence Analysis, DNA
                              • Sequence Homology, Nucleic Acid
                              • South America

                              Grant Funding

                              • Wellcome Trust

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