OH 89: A newly described ~1.8-million-year-old hominid clavicle from Olduvai Gorge

  1. Catherine E Taylor
  2. Fidelis Masao
  3. Jackson K Njau
  4. Agustino Venance Songita
  5. Leslea J Hlusko

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Abstract

Objectives  Here, we describe the morphology and geologic context of OH 89, a ∼1.8million-year-old partial hominid clavicle from Olduvai (Oldupai) Gorge, Tanzania. We compare the morphology and clavicular curvature of OH 89 to modern humans, extant apes, and a sample of other hominid fossil clavicles.  Materials and Methods  Comparative samples include 25 modern human clavicles, 30  Gorilla , 31  Pan , 7  Papio , and five hominid clavicles. Length regression on midshaft size using the extant comparative samples is used to estimate the total length of OH 89. A set of 9 linear measurements are taken from each individual. We also describe a new methodology for measuring clavicular curvature using measurements of sternal and acromial curvature, from which an overall curvature measurement is calculated. A principal component analysis (PCA) and a t-distributed stochastic neighbor embedding (tSNE) analysis are used to compare the morphology of OH 89 with the extant and fossil comparative samples.  Results  Our new method of measuring clavicular curvature successfully separates the different genera of the extant clavicles. The length estimate and sternal and acromial curve measurements for OH 89 falls within the larger male humans. The PCA shows OH 89 and most of the fossil hominids falling between the modern human and  Pan  groups, while the t-SNE suggests that OH 89, KSD-VP-1/1, KNM-ER 1808, and OH 48 are more similar to each other than to any of the other groups. This analysis also plots KNM-WT 15000 with the modern humans and Krapina 158 with the  Pan  individuals.  Discussion  The OH 89 clavicle derives from an individual of unknown hominid species with a shoulder breadth similar to that of a large human male. The curvature of OH 89 is relatively human-like relative to its length. Our new methodology for measuring clavicular curvature, combined with the utilization of t-SNE analyses and comparison of t-SNE results to PCA results, provides greater separation of genera than previously used methods, and wider use of t-SNE may be useful in paleoanthropological work.

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  1. Version published to 10.24072/pcjournal.372
  2. Peer Community in Paleontology

    The evolution of the hominid clavicle has not been studied in depth by paleoanthropologists given its high morphological variability and the scarcity of complete diagnosable specimens. A nearly complete Nacholapithecus clavicle from Kenya (Senut et al. 2004) together with a fragment from Ardipithecus from the Afar region of Ethiopia (Lovejoy et al. 2009) complete our knowledge of the Miocene record. The Australopithecus collection of clavicles from Eastern and South African Plio-Pleistocene sites is slightly more abundant but mostly represented by fragmentary specimens. The number of fossil clavicles increases for the genus Homo from more recent sites and thus our potential knowledge about the shoulder evolution. 

    In their new contribution, Taylor et al. (2023) present a detailed analysis of OH 89, a ~1.8-million-year-old partial hominin clavicle recovered from Olduvai Gorge (Tanzania). The work goes over previous studies which included clavicles found in the hominid fossil record. The text is accompanied by useful tables of data and a series of excellent photographs. It is a great opportunity to learn its role in the evolution of the hominid shoulder gird as clavicles are relatively poorly preserved in the fossil record compared to other long bones. The study compares the specimen OH 89 with five other hominid clavicles and a sample of 25 modern clavicles, 30 Gorilla, 31 Pan and 7 Papio. The authors propose a new methodology for measuring clavicular curvature using measurements of sternal and acromial curvature, from which an overall curvature measurement is calculated. The study of OH 89 provides good evidence about the hominid who lived 1.8 million years ago in the Olduvai Gorge region. This time period is especially relevant because it can help to understand the morphological changes that occurred between Australopithecus and the appearance of Homo. The authors conclude that OH 89 is the largest of the hominid clavicles included in the analysis. Although they are not able to assign this partial element to species level, this clavicle from Olduvai is at the larger end of the variation observed in Homo sapiens and show similarities to modern humans, especially when analysing the estimated sinusoidal curvature.

    References

    Lovejoy, C. O., Suwa, G., Simpson, S. W., Matternes, J. H., and White, T. D. (2009). The Great Divides: Ardipithecus ramidus peveals the postcrania of our last common ancestors with African apes. Science, 326(5949), 73–106. https://doi.org/10.1126/science.1175833

    Senut, B., Nakatsukasa, M., Kunimatsu, Y., Nakano, Y., Takano, T., Tsujikawa, H., Shimizu, D., Kagaya, M., and Ishida, H. (2004). Preliminary analysis of Nacholapithecus scapula and clavicle from Nachola, Kenya. Primates, 45(2), 97–104. https://doi.org/10.1007/s10329-003-0073-5

    Taylor, C., Masao, F., Njau, J. K., Songita, A. V., and Hlusko, L. J. (2023). OH 89: A newly described ∼1.8-million-year-old hominid clavicle from Olduvai Gorge. bioRxiv, 526656, ver. 6 peer-reviewed by PCI Paleo. https://doi.org/10.1101/2023.02.02.526656

  3. Version published to 10.1101/2023.02.02.526656 on bioRxiv