Laetoli’s lost tracks: 3D generated mean shape and missing footprints

Abstract

The Laetoli site (Tanzania) contains the oldest known hominin footprints, and their interpretation remains open to debate, despite over 35 years of research. The two hominin trackways present are parallel to one another, one of which is a composite formed by at least two individuals walking in single file. Most researchers have focused on the single, clearly discernible G1 trackway while the G2/3 trackway has been largely dismissed due to its composite nature. Here we report the use of a new technique that allows us to decouple the G2 and G3 tracks for the first time. In so doing we are able to quantify the mean footprint topology of the G3 trackway and render it useable for subsequent data analyses. By restoring the effectively ‘lost’ G3 track, we have doubled the available data on some of the rarest traces directly associated with our Pliocene ancestors.

Reevaluating the functional implications of Australopithecus afarensis navicular morphology

“…The 3D shape of the A. afarensis navicular is not predominantly African ape-like as previously suggested and instead shows modifications from a hypothetical African ape-like ancestral morphology in the direction of modern humans and other hominins, which does not support previous hypotheses regarding the evolution of the navicular (Lovejoy et al, 2009). In contrast to some prior suggestions (Tuttle, 1981(Tuttle, , 1985Tuttle et al, 1990Tuttle et al, , 1991Harcourt-Smith, 2002, 2005Harcourt-Smith and Aiello, 2004), the evidence derived from foot fossils (Latimer et al, 1987;Latimer and Lovejoy, 1989;Ward et al, 2011;Prang, 2015b) and footprint morphology (Leakey and Hay, 1979;Day and Wickens, 1980;White, 1980;White and Suwa, 1987;Bennett et al, 2009;Raichlen et al, 2010;Crompton et al, 2012;Bennett et al, 2016) supports the hypothesis that A. afarensis possessed a longitudinal arch. Although several recent studies suggest the Figure 9.…”

“…333-160) provided support for the hypothesis that A. afarensis had both longitudinal and transverse arches (Ward et al, 2011; but see Harmon, 2013 andMitchell et al, 2012 for alternative views), and a recent analysis of rearfoot angular relationships also found support for this hypothesis (Prang, 2015b). Thus, there are several lines of evidence based on foot morphology suggestive of a longitudinal arch in A. afarensis, which are congruent with the structural and functional inferences derived from the Laetoli footprints (Day and Wickens, 1980;White, 1980;White and Suwa, 1987;Bennett et al, 2009;Raichlen et al, 2010;Crompton et al, 2012;Bennett et al, 2016).…”

“…might be expected in the evolving hominin foot. Although recent quantitative studies on the morphology of the Laetoli footprints support the hypothesis that A. afarensis possessed a longitudinally arched foot, they also suggest that it was not as well developed as it is in modern humans (Bennett et al, 2009(Bennett et al, , 2016. Our understanding of the fossil hominin longitudinal arch is complicated by the fact that there is no living analog for extinct taxa such as A. afarensis.…”

“…Modern humans with a weak tibialis posterior have a lower longitudinal arch, increased midfoot plantar pressure, increased medial weight transfer, and increased rearfoot eversion (Neville et al, 2015). The fossilized footprints at Laetoli, Tanzania, display modern human-like characteristics, such as a relatively adducted hallux compared to chimpanzees, a deep impression associated with heel-strike, and a medial longitudinal arch (Leakey and Hay, 1979;Day and Wickens, 1980;White, 1980;White and Suwa, 1987;Bennett et al, 2009;Raichlen et al, 2010;Crompton et al, 2012;Bennett et al, 2016). However, more recent quantitative studies suggest the Laetoli footprints show less medial weight transfer than would be found in modern humans (Bennett et al, 2009(Bennett et al, , 2016Crompton et al, 2012;see also;DeSilva and Gill, 2013;DeSilva et al, 2015) and a longitudinal arch that was probably not as well developed as the modern human arch (Bennett et al, 2009(Bennett et al, , 2016).…”

“…333 site at Hadar, Ethiopia (Latimer et al, 1982). The Laetoli footprints provide nearly direct evidence of foot function in an early hominin taxon, displaying a longitudinal arch and a relatively adducted hallux compared to chimpanzees (Leakey and Hay, 1979;Day and Wickens, 1980;White, 1980;White and Suwa, 1987;Bennett et al, 2009;Raichlen et al, 2010;Crompton et al, 2012;Bennett et al, 2016). The discovery of a complete fourth metatarsal (A.L.…”