The paleoecology of the Upper Laetolil Beds, Laetoli Tanzania: A review and synthesis

The Upper Laetolil Beds of Laetoli, Tanzania (~3.6-3.85. Ma) has yielded a large and varied faunal assemblage, including specimens of Australopithecus afarensis. In contrast with contemporaneous eastern African A. afarensis sites in Kenya and Ethiopia, there is no indication of permanent rivers or other large bodies of water at the site, and the apparently drier environment supported a quite different faunal and floral community as reconstructed from the fossil record. Therefore, a deeper understanding of the paleoecology at Laetoli can be illuminating for questions of habitat access and use by A. afarensis, as well as its behavioral flexibility. This paper reviews the substantial body of evidence accumulated that allows for a detailed reconstruction of the Pliocene paleoenvironment of Laetoli. A synthesis of the different lines of evidence suggests that the Upper Laetolil Beds was a mosaic of grassland-shrubland-woodland habitats with extensive woody vegetation in the form of shrubs, thickets and bush, as well as a significant presence of dense woodland habitats along seasonal river courses and around permanent springs. The vegetation during the Pliocene at Laetoli was likely impacted by the strongly seasonal availability of water and the volcanic ash falls that periodically blanketed the area. A comparison with the paleoenvironments of other A. afarensis sites and a review of its inferred dietary behavior suggest that A. afarensis was an ecological generalist that was able to consume a wide variety of dietary resources in mosaic habitats, although their differential abundances at different sites may be indicative of specific ecological requirements that impact their success in particular environments.