Laetoli footprints reveal bipedal gait biomechanics different from those of modern humans and chimpanzees

Abstract

Bipedalism is a key adaptation that shaped human evolution, yet the timing and nature of its evolution remain unclear. Here we use new experimentally based approaches to investigate the locomotor mechanics preserved by the famous Pliocene hominin footprints from Laetoli, Tanzania. We conducted footprint formation experiments with habitually barefoot humans and with chimpanzees to quantitatively compare their footprints to those preserved at Laetoli. Our results show that the Laetoli footprints are morphologically distinct from those of both chimpanzees and habitually barefoot modern humans. By analysing biomechanical data that were collected during the human experiments we, for the first time, directly link differences between the Laetoli and modern human footprints to specific biomechanical variables. We find that the Laetoli hominin probably used a more flexed limb posture at foot strike than modern humans when walking bipedally. The Laetoli footprints provide a clear snapshot of an early hominin bipedal gait that probably involved a limb posture that was slightly but significantly different from our own, and these data support the hypothesis that important evolutionary changes to hominin bipedalism occurred within the past 3.66 Myr.

Obligate Bipedal Locomotion in the Modern Human: A Review of Musculoskeletal Modifications

“…These changes started to appear in Australopithecus afarensis at approximately 3.6 million years ago (Mya); it has been extensively studied via the Laetoli footprints ( Figure 1) discovered by Mary Leaky in 1978 near Olduvai Gorge in Tanzania [21][22][23]. On the other that hominids adaptations, particularly pelvic re-designing, were far different for example that of Oreopithecus bambolii [24].…”

The evolution of the human foot

“…afarensis. These footprints were made by bipedal hominins moving with an extended hip and extended knee, though perhaps with a gait different from that practiced by modern humans . The prints bear a strong resemblance to those made by modern humans today; however, there are several key differences.…”

“…These footprints were made by bipedal hominins moving with an extended hip and extended knee, 86 though perhaps with a gait different from that practiced by modern humans. 87 The prints bear a strong resemblance to those made by modern humans today 13,88 ; however, there are several key differences. One hominin (G1) experienced less medial weight transfer than is typically seen in humans 52,87 and analyses suggest that while the medial arch was present, it was likely reduced relative to most humans today.…”

“…87 The prints bear a strong resemblance to those made by modern humans today 13,88 ; however, there are several key differences. One hominin (G1) experienced less medial weight transfer than is typically seen in humans 52,87 and analyses suggest that while the medial arch was present, it was likely reduced relative to most humans today. 29,52,83 Additionally, consistent with Au.…”

These feet were made for walking

“…Others have contested this conclusion (e.g., Meldrum et al, 2011). In fact, a recent analysis strongly suggested that the Laetoli footprints were significantly different from those of a modern human walking barefoot, and actually in some ways more similar to chimpanzee footprints (Hatala et al, 2016). …”