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Major Events in Hominin Evolution

2016; Springer Nature; Linguagem: Inglês

10.1007/978-94-017-9597-5_8

2452-1639

Martin G. Lockley, Jeff Meldrum, Kyung Soo Kim,

Evolution and Paleontology Studies

The hominin footprint record spans ~3.6 Ma, from Late Pliocene to Holocene, and thus also spans a temporal duration corresponding to many of the major events in hominin evolution. While the oldest (~3.6 Ma) tracks from Laetoli (Tanzania) have been attributed, provisionally, to genus Australopithecus, all others are attributed to various species of the genus Homo, including H. erectus (H. ergaster), H. neanderthalensis, and H. sapiens. Recent reviews of the previously neglected hominin track record have demonstrated that more than 60 sites are documented in the literature, and that these are found on all continents (excepting Antarctica). Based on age, geographic location, and to a lesser degree footprint morphology, it is possible to infer which post-Laetoli sites and footprint assemblages represent H. erectus (H. ergaster), and which are attributable to later Homo species. However, distinguishing between H. sapiens and H. neanderthalensis on the basis of footprint morphology is not demonstrated conclusively. All the older sites (~3.6- Ma to ~117,000 yBP), from Africa and Europe, including those that represent pre-H. sapiens species, are “open-air” sites, whereas a number of younger, pre-Holocene sites (~62,000 to ~10,000 yBP), especially in Europe, are cave sites. With the exception of a very controversial site in Mexico dated at ~40,000 yBP, no other New World footprint sites are more than ~12,500 years old, and the oldest Australian sites are ~19,000–23,000 yBP. The extent to which significant modifications in the morphology of the hominin foot and corresponding footprints between 3.6 million and ~50,000 yBP has occurred continues to be debated, but there are two distinct polar morphologies (Praehominipes and Hominipes) now documented in the ichnologic literature. The question of whether transitions in such morphologic features as midfoot flexibility vs. a fully modern arch, and separation of the big toe from traces of lateral digits, and their inferred lengths, constitute evidence of major evolutionary changes may not be resolved to consensus without additions to pedal fossil remains and trace fossil record. In most cases, sites reveal associated tracks and traces of other tetrapods, mostly mammals and birds, as well as, in some instances, other hominin-manufactured artifacts. Such contextual trace fossil evidence is important for understanding the ecology of early hominin habitats. As recent studies have noted, there is no well-defined line between the hominin track record, narrowly defined as footprints, and the broader ichnologic record, which includes cut marks on bone, handprints, paintings in caves, and even various artifacts. Paleolithic cave paintings that depict tracks and associated track makers could be considered as the earliest examples of vertebrate ichnology field guides, although the significance to the artists themselves likely differed from our modern notion of a guidebook. Although not normally thought of as part of the track record, footprints on the Moon, as well as the tracks of lunar vehicles, and robotic vehicles employed on Mars, represent the ichnologic signatures of recent major events in hominin evolution.