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Study reveals four stages of human body evolution

Research into 430,000-year-old fossils collected in northern Spain found that the evolution of the human body's size and shape has gone through four main stages, according to a paper published this week.

Study reveals four stages of human body evolution
SH-selected postcranial traits [Credit: PNAS]
A large international research team including Binghamton University anthropologist Rolf Quam studied the body size and shape in the human fossil collection from the site of the Sima de los Huesos in the Sierra de Atapuerca in northern Spain. Dated to around 430,000 years ago, this site preserves the largest collection of human fossils found to date anywhere in the world.

The researchers found that the Atapuerca individuals were relatively tall, with wide, muscular bodies and less brain mass relative to body mass compared to Neanderthals. The Atapuerca humans shared many anatomical features with the later Neanderthals not present in modern humans, and analysis of their postcranial skeletons (the bones of the body other than the skull) indicated that they are closely related evolutionarily to Neanderthals.

"This is really interesting since it suggests that the evolutionary process in our genus is largely characterized by stasis (i.e. little to no evolutionary change) in body form for most of our evolutionary history," wrote Quam.

Comparison of the Atapuerca fossils with the rest of the human fossil record suggests that the evolution of the human body has gone through four main stages, depending on the degree of arboreality (living in the trees) and bipedalism (walking on two legs). The Atapuerca fossils represent the third stage, with tall, wide and robust bodies and an exclusively terrestrial bipedalism, with no evidence of arboreal behaviors. This same body form was likely shared with earlier members of our genus, such as Homo erectus, as well as some later members, including the Neanderthals. Thus, this body form seems to have been present in the genus Homo for over a million years.

It was not until the appearance of our own species, Homo sapiens, when a new taller, lighter and narrower body form emerged. Thus, the authors suggest that the Atapuerca humans offer the best look at the general human body shape and size during the last million years before the advent of modern humans.

The study was published in Proceedings of the National Academy of Sciences.

Source: Binghamton University [August 31, 2015]
TANN

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1 comment :

  1. There are indeed schematically 4 postcranial clusters in hominid (Pan-Homo-Gorilla) evolution, which could be called: ape, apith, archaic, sapiens. But not in *human* evolution s.s.: the evolution of the human body has not gone through 4 stages, depending on the degree of arboreality & bipedalism, as the authors state: we did not evolve from creatures like the extant apes, but both humans & chimps had more apith-like ancestors c 5 Ma, who were not to various degrees arboreal or bipedal (in fact, gibbons are both), but whose fossils are typically found in wetlands (e.g. K.Reed). Lowland gorillas regularly wade on 2 legs in forest swamps (google Ndoki gorilla) in search for frogbit or sedges, and the australopithecines (apith) apparently waded upright or floated vertically while collecting aquatic herbaceous vegetation (AHV) & hard-shelled invertebrates (HSIs) & climbed vertically in the branches above the swamp (google aquarboreal). From such ancestors, both Pan & Gorilla in parallel evolved knuckle-walking during the colder & drier Pleistocene (ice ages). Homo followed a very different evolutionary path (google econiche Homo): when the sea-levels dropped during the Glacials (after c 2.6 Ma), extensive tree-poor & shellfish-rich territories became available on the continental shelves for handy & tool-using hominids, who spread along the African & Eurasian coasts (+ later along rivers), beach-combing, diving & wading bipedally for littoral, shallow-aquatic & waterside foods (shellfish is rich in brain-specific nutrients, e.g. DHA, Cunnane 2005): this explains the "archaic" features of H.erectus (& later the Atapuerca & Neandertal fossils along the rivers): reduction of climbing adaptations (e.g. larger hip joints), brain expansion (DHA), very thick & dense bones (littoral mammals), long low flat skull (idem), external nose (semi-aquatic), ear exostoses (diving humans), island colonization (e.g. Flores & Medit.islands), intercontinental diaspora (coastal dispersal, Munro 2010) etc.
    IOW, it was not ape-->apith-->archaic-->sapiens (anthropocentrism), but schematically OT1H apith-->Pan & apith-->Gorilla, and OTOH apith-->archaic-->sapiens. Late-Pleistocene H.sapiens lost diving adaptations (thick bones, flat skull etc.), they became shallow water waders with spears etc., collecting not only shellfish & waterside carcasses of ungulates & stranded whales, but learnt to fish, high above the water with distance weapons, and collected all sorts of waterside foods (e.g. rice). That our ancestors did not run over the plains, sweating water + salt (scarce in savannas) as outdated versions of hmuan evoluton still claim, but followed the coasts & later rivers is now being confirmed in a lot of recent PA papers, e.g.
    -J.Joordens, S.Munro cs 2015 Homo erectus at Trinil on Java used shells for tool production and engraving, Nature 518:228-231,
    -M.Verhaegen, S.Munro 2011 Pachyosteosclerosis suggests archaic Homo frequently collected sessile littoral foods, HOMO 62:237-247,
    -M.Verhaegen 1987 Origin of hominid bipedalism, Nature 325:305-6,
    -S.Munro 2010 Molluscs as ecological indicators in palaeoanthropological contexts, PhD thesis Univ.Canberra,
    -J.Joordens cs 2009 Relevance of aquatic environments for hominins: a case study from Trinil, J.hum.Evol.57:656-671,
    -M.Gutierrez cs 2001 Exploitation d’un grand cétacé au Paléolithique ancien (Benguela, Angola), CRAS 332:357-362,
    -K.Choi, D.Driwantoro 2007 Shell tool use by early members of Homo erectus in Sangiran: cut mark evidence, J.archaeol.Sci.34:48-58,
    -S.Cunnane 2005 Survival of the fattest: the key to human brain evolution, World Scient.Publ.,
    -M.Vaneechoutte cs eds 2011 Was Man more aquatic in the past? eBook Bentham,
    -P.Rhys Evans cs eds 2013-2014 Human Evolution conference London May 2013 proceedings, special editions Hum.Evol.28 & 29 (google researchGate marc verhaegen).

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