Ecological implications of the relative rarity of fossil hominins at Laetoli

Denise F. Su, Terry Harrison

    Research output: Contribution to journalArticle

    Abstract

    Hominins are a very rare component of the large-mammal fauna at Laetoli. Although no equivalent data are available for Hadar, the much higher count and relative abundance of hominins suggests that they may have been more common at the latter site. The apparent relative rarity of hominins at Laetoli may have significant implications for understanding the ecology of Australopithecus afarensis. However, it is essential to first assess the extent to which taphonomic variables might have been a contributing factor. Using data from fossil ruminants, we show that the survivability of skeletal elements at Laetoli relates to the extent to which they can resist carnivore scavenging and their likelihood of being entirely buried by volcanic ashes and tuffaceous sediments. The rarity of hominins at Laetoli is probably due in part to the influence of these two taphonomic factors. However, these factors cannot account entirely for the difference in hominin relative abundance between these two sites, and ecological differences were probably a contributing factor. The highest population densities of chimpanzees today occur in forest and closed woodland, with reduced densities in open woodland. If similar levels of population-density variation characterized A. afarensis, the differences between Hadar and Laetoli may relate to the quality/optimality of the habitats. Hadar was, in general, much more densely wooded and mesic than Laetoli, with permanent and substantial bodies of water. In contrast, Laetoli was predominantly a woodland-shrubland-grassland mosaic supported only by ephemeral streams and ponds. The apparent greater relative abundance of hominins at Hadar compared with Laetoli suggests that, like chimpanzees, A. afarensis may have been more successful in more densely wooded habitats. Compared with Hadar, Laetoli probably represented a less optimal habitat for the foraging and dietary behavior of A. afarensis, and this is reflected in their inferred lower abundance, density, and biomass.

    Original languageEnglish (US)
    Pages (from-to)672-681
    Number of pages10
    JournalJournal of Human Evolution
    Volume55
    Issue number4
    DOIs
    StatePublished - 2008

    Fingerprint

    rarity
    habitat
    woodlands
    relative abundance
    woodland
    fossils
    fossil
    population density
    Pan troglodytes
    habitats
    ephemeral streams
    bodies of water
    ephemeral stream
    ephemeral pool
    volcanic ash
    ruminant
    shrubland
    carnivore
    eating habits
    carnivores

    Keywords

    • Australopithecus afarensis
    • Carnivores
    • Paleoecology
    • Ruminants
    • Taphonomy

    ASJC Scopus subject areas

    • Ecology, Evolution, Behavior and Systematics
    • Education
    • Arts and Humanities (miscellaneous)

    Cite this

    Ecological implications of the relative rarity of fossil hominins at Laetoli. / Su, Denise F.; Harrison, Terry.

    In: Journal of Human Evolution, Vol. 55, No. 4, 2008, p. 672-681.

    Research output: Contribution to journalArticle

    Su, Denise F. ; Harrison, Terry. / Ecological implications of the relative rarity of fossil hominins at Laetoli. In: Journal of Human Evolution. 2008 ; Vol. 55, No. 4. pp. 672-681.
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