which of these features of hominins evolved most recently?

Human Evolution - Historical Geology 2003). They developed a capacity for language about 50,000 years ago. Any species considered to be more closely related to humans than chimpanzees we call hominins. Molecular evidence indicates that the last common ancestor of the genus Pan and the hominin clade existed between 8 and 4 million years ago (Ma). From Biped to Strider: The Emergence of Modern Human Walking, Running, and Resource Transport. - Most of the traits that are found in humans but not apes evolved after hominins arose. The conditions present in H. erectus remain unresolved (see text). in time of what things may have been like during that time. 2003; Tocheri, 2007), which is the inferred primitive condition in the Pan-Homo LCA. 288-1) from the Hadar Formation, Ethiopia. Plio-Pleistocene tool-making and the transport of resources. Behrens T. E. J., Hunt L. T., Rushworth M. F. S. Early Homo brain morphology is characterized by increases in the frontal and temporal lobe, both of which are heavily implicated in social tasks [36,37,79,80]. It is not our specific charge to evaluate the models for the Pan-Homo LCA locomotor regime in detail or to review the literature on the functional morphology of the hominid hand in relation to locomotor forelimb postures (see Crompton et al. First hominid from the Miocene (Lukeino Formation, Kenya). Federal government websites often end in .gov or .mil. The second process is the consequence of an increasingly unpredictable climate, which has been labelled as the variability selection hypothesis [7,8], whereby extreme fluctuations in the environment created dynamic and inconsistent habitats over time. The other individuals all show similar characteristics, and over a time range that now extends from as long ago as 95,000 years to as recently as 13,000 years ago a population of 'hobbits . The relationship between PCSA, Forearm flexor mass relative to forearm extensor mass, Little can be inferred. A key issue remains as to whether environmental pressures are ultimately the cause of changes in the other selection pressures that influence brain size. In: Isaac GL, McKown ER, editors. lateral line system To accomplish our goal, we first tentatively infer the morphology most likely present in the last common ancestor (LCA) of the genus Pan and the hominin clade (hereafter referred to as the Pan-Homo LCA) using relevant comparative information from extant primates, particularly species of Pongo, Gorilla, Pan, and Homo. hominin traits and what exactly they may tell us about human evolution, it is Although no scaphoids or trapezoids have been described for Australopithecus, the surrounding anatomy observed on the trapezium, second metacarpal bases, and capitates all suggest that features f, H, J, K, and L also remain primitive (Tocheri, 2007) an indirect inference that is supported by direct evidence from OH 7 and H. floresiensis (Tocheri et al. Tocheri MW. The current fossil evidence does, however, provide some interesting clues as to when and where particular changes in hominin hand morphology may have occurred. Humans are hominoids. Evidence that social group size changed in steps concurrently with brain size changes would more conclusively support the social brain hypothesis. Nor is there consistent evidence at the super-species level to support either the variability selection or the aridity hypotheses using sea-level indicators (table 2). Expansion of superficial head origin to the flexor retinaculum; distinct deep head originates from the trapezoid, capitate and palmar ligaments. 2002, 2004; Wimmer et al. It appears comparatively proximo-distally short relative to the expected size as reflected by the trapezium and scaphoid and is most likely from a smaller individual than the trapezium and scaphoid. Since our ancestors were hunters and gathers, they did a lot of walking We also performed step-wise regression with multiple palaeoclimate records over all homninins and at the species level. Attempts have been made to infer muscle size in fossil taxa from the size of fossae and ridges on the phalanges of digits 25. H. sapiens migrated to southern China between 120 kya and 80 kya and Europe about 4543 kya. Tuttle RH. The adaptive link between such features and knuckle-walking must be shown by (1) establishing that such features are derived relative to the morphology of appropriate non-knuckle-walking out-groups; (2) demonstrating through functional morphological studies that the features are biomechanically advantageous for the behavior of knuckle-walking relative to the inferred most recent primitive condition; and (3) where possible showing that comparable features evolved independently in animals that use similar locomotor hand postures (e.g. 1999: p. 509). In some cases, features may reflect the presence, absence or relative size of a particular muscle, whereas in other cases, bone morphology may influence muscular mechanics by altering the direction or path of tendons relative to the inferred primitive condition. Throughout their tenures, both the archaic and descendant populations interbred with contemporaries from other areas. Of the latter pair, the first coincides with the appearance of the AMHs approximately 195 kya, but the second does not coincide with a species appearance. Schultz AH. 1991; Niewoehner et al. Associated cranial and forelimb remains attributed to. Rightmire GP. 2010. Begun DR. Relations among the great apes and humans: New interpretations based on the fossil great ape. 2001) and an adult distal thumb phalanx (BAR 190101) (Gommery & Senut, 2006) attributed to Orrorin. erectus as both hominin genera are represented at this South African site (Trinkaus & Long, 1990). official website and that any information you provide is encrypted Without language, it is not possible to share symbolic ideas or to impart knowledge about events removed in space or time. Together, the molecular and fossil evidence has important consequences for interpreting the evolutionary history of the hand within the tribe Hominini (hominins). Leakey LSB, Tobias PV, Napier JR. A new species of the genus, Leakey MG, Feibel CS, McDougall I, Ward C, Walker A. 1982). In this scenario, demography allows a scaffolding of underlying gradual accumulated changes in technology and cognitive ability [83]. 333-40, KNM-WT 22944-H) and Au. evolves, hominid skull capacity does not change in any substantial way. Here, we briefly review these hypotheses. The same inferential process holds for testing the suspensory or climbing model for the Pan-Homo LCA, but such models have additional challenges because of key similarities between modern human and African ape hand morphology (Corruccini, 1978; Begun, 1992, 2004; Richmond et al. Using genetic evidence to evaluate four palaeoanthropological hypotheses for the timing of Neanderthal and modern human origins, Latitudinal variation in light levels drives human visual system size, The Phanerozoic record of global sea-level change. (1999) demonstrated that modern humans are derived in having significantly longer muscle moment arms (around at least one of the anatomical axes of rotation) for several of the muscles of the hand including opponens pollicis, adductor pollicis (oblique and transverse heads), flexor pollicis brevis (superficial head), abductor pollicis longus, abductor pollicis brevis, and extensor pollicis longus. Schmitt D. Insights into the evolution of human bipedalism from experimental studies of humans and other primates. There are four basic models that purport to explain the evolution of H. sapiens between about 315 and 30 kya. [see Constantino & Wood, 2007]), Homo floresiensis, Homo erectus sensu lato, Homo antecessor, Homo neanderthalensis, and Homo sapiens. 1992; Drapeau et al. In contrast, this period is followed by a veritable explosion of material and symbolic culture, increasingly sophisticated technologies and long transport distances. The origin and evolution of humans have been the main focus of biological and anthropological research during the last 150 years 1,2,3.Most of the previous studies have focused on species . The recovered proximal phalanges are relatively straight (Lorenzo et al. South Turkwel: a new Pliocene hominid site in Kenya. 2.5-million-year-old stone tools from Gona, Ethiopia. Comparative osteometrics of the hominoid wrist joint, with special reference to knuckle-walking. In: Harvati K, Harrison T, editors. Tocheri MW, Razdan A, Williams RC, Marzke MW. Population density increases could result from either ecological or social changes (i.e. Fossil Mammals of Africa No. The appearance of early Homo was also associated with profound changes in life history, as well as body size and shape. Molecular phylogeny and dating of early primate divergences. 2011. Dissection photos of tendons that insert into the palmar portions of the thumb distal phalanx in nonhuman primates (radial is toward page top and distal is toward page left). Brain size change at approximately 100 kya is coincident with demographic change and the appearance of fully modern language. As only limited insight into behaviour is available from the archaeological record, much of our understanding of historical changes in human cognition is restricted to identifying changes in brain size and architecture. Single superficial head that originates from the trapezium. Environment likely played a part, whether as a direct pressure or by forcing hominins to change their behaviour so as to be able to use more risky and peripheral habitats, to live in larger groups, or to use novel resources. 2005), and their pisiforms are long and rod-shaped (Table 1, Q; Bush et al. Morwood MJ, Soejono RP, Roberts RG, et al. We can also get a look at For example, prominent volar fossae of the distal phalanx of the thumb have been described for fossil specimens such as Stw 294 from Sterkfontein attributed to Au. With future work it may be possible to predict forearm muscle masses from bony markings. There are more hand fossils for Au. I thought the fossil of Lucy was extremely interesting since she was part primate and part human. Factors indicating H. rudolfensis as ancestral to later species of Homo are its absolute brain size, large body, and lower limb morphology.These features clearly foreshadow younger species of Homo in Africa and Eurasia.However, a mandible discovered in the Ledi-Geraru area of the Awash River valley in 2013 may point toward a different ancestorone that clearly belongs to the genus Homo. Thus, this latter feature in OH 7 may represent (1) a reversal to the primitive state, (2) the presence of a fossil lineage that diverged prior to the split of Australopithecus, or (3) the condition in Au. Functional morphology of the midcarpal joint in knuckle-walkers and terrestrial quadrupeds. Fecal transplants will make people sick. Thus, one argument may be that it was the cognitive demands of language per se that drove hominin brain evolution. Neither of the palaeoclimate records that we use explain the stepwise changes in brain size at approximately 1.8 Mya or 100 kya. The appearance of H. erectus and H. sapiens in Eurasia is associated with further gradual increases over time. It is so interesting to see how our ancestors or former species used to look like and behave like. Middle phalanx skeletal morphology in the hand: can it predict flexor tendon size and attachments? Human Origins: Louis Leakey and the East African Evidence. Ph.D. Dissertation, State University of New York at Stony Brook, Stony Brook. The derived hominin condition is an enlarged, palmarly placed joint between the trapezoid and capitate regardless of whether an articular surface is retained dorsally (Table 1, l) (Lewis, 1989; Tocheri, 2007); this is, in part, due to the combined effects of the shape change of the trapezoid from a primitive pyramidal wedge-shape (which by definition cannot have an enlarged, palmarly placed articular surface) to a derived boot-shape. Here, we briefly review these hypotheses. Morphology of the Pliocene partial hominid skeleton (A.L. Fossils, feet and the evolution of human bipedal locomotion 2004; Kumar et al. For this reason, terrestrial primates live in much larger groups than arboreal species; this is especially true of species that are typically found in open habitats [16]. Powell J. L., Lewis P. A., Dunbar R. I. M., Garca-Fiana M., Roberts N. more. Thus, Job is the feature of a human community that is similar to a niche in a biological community. These differences in modern humans may be due to the supinated position of the trapezium within the modern human wrist, which is a consequence of the palmar expansion of the trapezoid (Table 1, j) and is further recognized by the extension of the trapezium joint surface onto the scaphoid tubercle (Table 1, h) (Lewis, 1989; Tocheri, 2007). Primate, and Mammal Evolution, eds. Quantifying temporal bone morphology of great apes and humans: an approach using geometric morphometrics. Moreover, our analyses suggest that the processes that have acted on encephalization in Eurasia differed from those in Africa. What is most clear is that the hands of modern humans and Neandertals show more shared derived features relative to the Pan-Homo LCA than any other hominin taxa. are now molars. S.S. is supported by a Royal Society Dorothy Hodgkin Fellowship. Howell AB, Straus WL. 2007a,b). Therefore, we have no way of knowing which of these features were more likely present in the human-Neandertal LCA, an unfortunate fact which is confounded further due to the paucity of information about the hands of H. erectus sensu lato and other Middle Pleistocene hominins. Eizirik E, Murphy WJ, Spinger MS, OBrien SJ. New. Other selections assume that most features shared by Gorilla and Pan are probably homologous and thus would have appeared in the Gorilla-Pan-Homo LCA (Fig. The hypothetical ancestors at Nodes 10 and 11 are derived in comparison with the hypothetical ancestors at Nodes 7, 8, and 9 with respect to the majority of features examined. Vrba ES. Debate over the pre-bipedal locomotor mode for the hominin cladespecifically whether the Pan-Homo LCA was a terrestrially adapted knuckle-walker or a primarily arboreal climber/clamberer may appear to obscure reconstruction of the hand morphology in the Pan-Homo LCA. The aforementioned issues notwithstanding, these fossils provide details about hominin hand morphology between approximately 2.0 and 1.5 Ma (Leakey et al. Marzke et al. 2012. adapted to our environment over time. Not only this, but we are able to extrapolate Our re-evaluation of the enduring mystery about what drove human encephalization has not identified a smoking gun. 2002). This allows for a feedback process in which language itself became a selection pressure for increases in brain size. 2007a,b). Joint function and grips of the. Susman RL. Conversely, if brain size has changed as a result of a series of punctuated events, there should be periods of fast growth (associated with large step changes and positive residuals) followed by periods with no size change. 1999b), Australopithecus afarensis (Bush et al. Interestingly, orangutans may show a tendon with a similar insertion and function as FPL, but with an origin from the adductor pollicis oblique head rather than from the extrinsic muscle mass passing through the carpal tunnel (Fig. indet. If so, then periods of rapid brain size change should be associated with corresponding periods of changes in climate or in climate envelopes. 1981. Biostratigraphy and chronology, based particularly on Bovidae, of southern hominid-asociated assemblages: Makapansgat, Sterkfontein, Taung, Kromdraai, Swartkrans; and also Elandsfontein (Saldanha), Broken Hill (now Kabwe) and Cave of Hearths. 2, e) (Kivell & Begun, 2007). Musgrave JH. My evidence is that I think poop is . It was therefore a very useful term to designate the line leading to modern humans and was used when referring to various members of our human evolutionary tree. Using 200 ky blocks, we finally evaluated whether there were differences in tempo between hominins in Africa and those in Eurasia, owing to limited sample sizes for dates older than 200 kya. Accessibility Ontogeny and biomechanics of phalangeal form in primates. Before anamensis) show configurations that are derived relative to Pan, Gorilla, and the Pan-Homo LCA. (C) The right thumb of a baboon showing a FPL tendon bifurcating within the carpal tunnel from the ulnar side of the FDP tendon for the middle finger (other arrow) and crossing radially over the FDP tendon to the index finger as it exited the carpal tunnel distally. 2007). The steps in brain size at 100 kya and at 200400 kya are clearly driven by the migration of African hominin species into Eurasia. 438-1e, A.L. A community-level evaluation of the impact of prey behavioural and ecological characteristics on predator diet composition, Lemur social behavior and primate intelligence, The Oxford handbook of social neuroscience, Social cognition and cortical function: an evolutionary perspective, Action, perception and the brain: adaptation and cephalic expression, Neocortex size and behavioural ecology in primates, Neocortex size, group-size, and the evolution of language, The social brain hypothesis and its implications for social evolution, The symbolic species: the co-evolution of language and the brain. 1964; Leakey, 1971; Wood, 1974; Day, 1976; Constantino & Wood, 2007). At one extreme is multiregional evolution, or the regional continuity model. Terrestrial traits in the hands and feet of gorillas. In: Meldrum DJ, Hilton CE, editors. mitochondrial DNA The hybridization-and-replacement model proposes some interbreeding with archaic indigenous populations but with relatively minor effects.
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