A new hominin foot from Ethiopia shows multiple Pliocene bipedal adaptations

Journal name:
Nature
Volume:
483,
Pages:
565–569
Date published:
DOI:
doi:10.1038/nature10922
Received
Accepted
Published online

Abstract

A newly discovered partial hominin foot skeleton from eastern Africa indicates the presence of more than one hominin locomotor adaptation at the beginning of the Late Pliocene epoch. Here we show that new pedal elements, dated to about 3.4 million years ago, belong to a species that does not match the contemporaneous Australopithecus afarensis in its morphology and inferred locomotor adaptations, but instead are more similar to the earlier Ardipithecus ramidus in possessing an opposable great toe. This not only indicates the presence of more than one hominin species at the beginning of the Late Pliocene of eastern Africa, but also indicates the persistence of a species with Ar. ramidus-like locomotor adaptation into the Late Pliocene.

At a glance

Figures

  1. Location map of the Burtele (BRT) vertebrate localities (BRT-VP-1 and BRT-VP-2) in the Woranso-Mille study area.
    Figure 1: Location map of the Burtele (BRT) vertebrate localities (BRT-VP-1 and BRT-VP-2) in the Woranso-Mille study area.

    The path of the measured section through the sandstone ridges and the location of the mesa section with the dated Burtele tuff are shown. The measured basalt section is off the map. The study area is located about 30miles north of Hadar and Gona.

  2. Pedal elements of BRT-VP-2/73.
    Figure 2: Pedal elements of BRT-VP-2/73.

    a, Dorsal view of all elements of the specimen. b, Dorsal, plantar, lateral, medial, distal and proximal views of the first metatarsal. c, Dorsal, lateral, medial, proximal and distal views of the second metatarsal. d, Dorsal, lateral, plantar, distal and proximal views of the hallucal proximal phalanx. e, Lateral views of the second and fourth proximal phalanges, and the second intermediate phalanx. f, Dorsal, plantar and lateral views of the fourth metatarsal. All views are from left to right.

  3. Box-and-whisker plots of pedal element comparative ratios in cercopithecines, colobines, chimpanzees, gorillas, humans and fossil specimens.
    Figure 3: Box-and-whisker plots of pedal element comparative ratios in cercopithecines, colobines, chimpanzees, gorillas, humans and fossil specimens.

    (See Supplementary Table 6 for taxonomic composition.) Whisker lines indicate maximum and minimum values. a, Base height (PDP) of the first metatarsal to its length (L). b, Base height of the first metatarsal to base height of the second metatarsal. c, Hallucal length to the second metatarsal length. d, Hallucal length to the fourth metatarsal length. e, Base height of the second metatarsal to its length. f, Length of the second metatarsal to the length of the fourth metatarsal. Measurements of the South African and Miocene hominoids were taken from refs 10 and 17, respectively.

  4. Principal component analysis (PCA) of metatarsal ratios.
    Figure 4: Principal component analysis (PCA) of metatarsal ratios.

    Both PC1 and PC2 for 11 metatarsal ratios (descriptions of the ratios are provided in Supplementary Table 1) discriminate anatomically modern humans and apes from monkeys on the one hand and chimpanzees from anatomically modern humans and gorillas on the other. BRT-VP-2/73 falls in the human/gorilla cluster. Both components are heavily influenced by ratios 6, 9 and 10, which are all associated exclusively with dimensions of the hallux (see Supplementary Information for further discussion).

  5. Stratigraphic section at the BRT localities and placement of the BRT-VP-2/73 partial foot skeleton.
    Figure 5: Stratigraphic section at the BRT localities and placement of the BRT-VP-2/73 partial foot skeleton.

    The Burtele tuff is dated by the 40Ar/39Ar method to 3.469±0.008Myr ago and lies a maximum of about 27m below BRT-VP-2/73, providing a maximum age constraint of ~3.47Myr ago for the foot specimen (shown by the black star) and for three fossiliferous sandstone horizons (shown by vertical lines) at BRT-VP-1 and BRT-VP-2. An approximate age for the foot specimen, using regional sediment accumulation rates, suggests an age of between 3.2 and 3.4Myr ago for BRT-VP-2/73 (see Methods for details). S, F, M, C, P indicates soil, flaggy, mudstone, coarse and pebbly sandstone, respectively; it shows the degree of resistance to erosion and rock stiffness.

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Author information

Affiliations

  1. The Cleveland Museum of Natural History, Cleveland, Ohio 44106, USA

    • Yohannes Haile-Selassie
  2. Case Western Reserve University, Cleveland, Ohio 44106, USA

    • Yohannes Haile-Selassie,
    • Beverly Z. Saylor &
    • Bruce M. Latimer
  3. Berkeley Geochronology Center, Berkeley, California 94720, USA

    • Alan Deino
  4. Johns Hopkins University, Baltimore, Maryland 21218, USA

    • Naomi E. Levin
  5. Addis Ababa University, PO Box 1176 Addis Ababa, Ethiopia

    • Mulugeta Alene

Contributions

Y.H.-S. and B.M.L. conducted the description and comparative analysis. B.Z.S., N.E.L. and M.A. compiled the stratigraphic sequence. A.D. conducted the radiometric dating. N.E.L. conducted stable isotope analysis. Y.H.-S. and B.M.L. wrote the paper with input from all authors.

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The authors declare no competing financial interests.

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Supplementary information

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  1. Supplementary Information (5.2M)

    This file contains Supplementary Figures 1-7, Supplementary Text, Supplementary Tables 1-10 and Supplementary References.

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