which of these features of hominins evolved most recently?

Alternative avenues for estimating social group size, such as artefact deposition rates, hominin assemblage numbers [14], hearth/site sizes, are fraught with potential biases, which makes their use hard to justify especially when comparing over wide time periods. Of the earliest members of the genus Homo, the best-known species are Homo habilis, Homo rudolfensis, and Homo erectus (Table 1 ). Susman RL, Creel N. Functional and morphological affinities of the subadult hand (OH 7) from Olduvai Gorge. In most hylobatids, the FPL tendon arises from a muscle belly that is separate from the FDP muscle to the fingers (Marzke, 1971), but in baboons it bifurcates within the carpal tunnel from the ulnar side of the FDP tendon for the middle finger and crosses radially over the FDP tendon to the index finger as it exits the carpal tunnel distally (Fig. Notice that this is different than trying to find modern human-like characteristics in these hominins (e.g. Several aspects of the modern human hand musculature appear derived in relation to the inferred condition of the LCA with Pan(Table 2). The derived hands of modern humans and Neandertals may indicate a morphological commitment to tool-related manipulative behaviors beyond that observed in other hominins, including those (e.g. Wrangham R. W., Jones Holland J., Laden G., Pilbeam D., Conklin-Brittain N. 1992; Drapeau et al. The second metacarpal bases (A.L. afarensis are short, relative to the length of the thumb (Marzke, 1983; Alba et al. We revaluated patterns of hominin brain size change and demonstrate that, rather than being a monotonic increase, hominin brain size increase is dominated by step changes with limited evidence for long-term gradual increases. Man's posture: its evolution and disorders. Within anthropoid primates, there is a strong correlation between group size and brain size [30,31]; Aiello & Dunbar [32] extrapolated this relationship to predict social group size in hominin species (for revised estimates, see Dunbar [33]). 1. Gibbs S, Collard M, Wood B. Soft-tissue characters in higher primate phylogenetics. The knuckle-walking anteater: a convergence test of adaptation for purported knuckle-walking features of African Hominidae. 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 . Most importantly, Dart noted that the forward position of the foramen magnum indicated that the skull was poised on top of the vertebral column, suggesting bipedalism and an upright posture. suggests the following conclusions. For instance, H. ergaster may have been the first hominin to reach Eurasia. However, although the demonstration of homology for hand features in African apes and modern humans is a necessary condition for testing the hypothesis that the LCA was a knuckle-walker (Richmond & Strait, 2000; Richmond et al. The trapezoid (LB 1-47) is wedge-shaped (Table 1, J) and its articulation with the capitate (LB 1-45) is relatively small and more dorsally placed (Table 1, L) (Tocheri et al. Homoiological features mimic potential homologies or homoplasies through phenotypic plasticity via common epigenetic factors such as a common developmental program coupled with a similar mechanical environment (Lycett & Collard, 2005; Collard & Wood, 2007). Noonan JP, Coop G, Kudaravallis S, et al. Older than the Oldowan? Thus, the first traces of modernity coincide with, or shortly precede, the period of a marked change in brain size. For example, the Australopithecus afarensis hand is likely derived in comparison with that of the PanHomo last common ancestor in having shorter fingers relative to thumb length and more proximo-distally oriented joints between its capitate, second metacarpal, and trapezium. Federal government websites often end in .gov or .mil. 2000, 2002; Page & Goodman, 2001; Lockwood et al. Within Africa, brain size increases at a roughly consistent rate, whereas the introduction of migrants into Eurasia creates periodic step-wise changes. A tendency toward gracilization of the phalanges may be a more recent autapomorphy of modern humans, but more study is needed. Together, the molecular and fossil evidence has important consequences for interpreting the evolutionary history of the hand within the tribe Hominini (hominins). The current fossil evidence available for Hominini gen. et sp. This includes identifying the conditions present in each taxon relative to the Pan-Homo LCA. 2004, 2005; Almcija et al. This task is complicated by uncertainties regarding the possible homologous, homoplastic, or homoiologic nature of hand features within the Hominidae, as well as uncertainties regarding the principal locomotor behavior of the Pan-Homo LCA. This evidence suggests that all hominin species descended from the hypothetical ancestors present at Nodes 4 through 9 (Figs 4, ,5)5) will also likely show similar scaphoid morphology, unless the scaphoid has become uniquely derived (autapomorphic) within a particular hominin lineage. Interestingly, although AMH first appeared in Africa around 200 kya, signatures of behavioural (and cognitive) modernity in the archaeological record remain uncommon for a protracted period following their arrival. However, this idea has been largely dismissed on the grounds that there is no evidence for any correlated brain size changes [88,89]. 2005), and their pisiforms are long and rod-shaped (Table 1, Q; Bush et al. Fleagle et al. 2003). 1982), Paranthropus (Susman, 1989), H. habilis (Napier, 1962; Susman & Creel, 1979), H. erectus/ergaster(Walker & Leakey, 1993), and H. antecessor(Lorenzo et al. These earliest hominins lack derived features found in later hominins, . Humans are hominoids. 438-1e, A.L. The South African ape-men: the Australopithecinae. 2007), the current fossil evidence for the genus Australopithecus suggests that the remaining 13 features of the hand are essentially unchanged from the inferred primitive conditions in the Pan-Homo LCA (Table 1; Fig. The most obvious candidates are in the archaeological record, which has traditionally begun with the appearance of Paleolithic (Old Stone Age) tools about 2.5 mya. Humans are a young species, in geological terms. These primitive hand features were also probably present in the hypothetical ancestors at Nodes 4 through 9 (Figs 4, ,5),5), which include the Pan-Homo LCA. Moreover, there is also the real possibility that other species of catarrhine or even hominid are also represented at these sites, and it is not always straightforward to differentiate isolated primate hand bones from one another, phalanges in particular (Begun, 1993). The significant differences in the residuals mirror the differences in log10CC (i.e. using teeth). The term 'hominid' used to have the same meaning that 'hominin' now has. Markings on Neandertal first metacarpals indicate that they also share DI1 pollical morphology with modern humans (Musgrave, 1971). Because there is sufficient fossil and comparative evidence for these 17 features, the likely conditions present at particular nodes within the hominin clade can also be reasonably resolved. Origin of human bipedalism: The knuckle-walking hypothesis revisited. Begun DR. Miocene fossil hominids and the chimp-human clade. Finally, we conclude with a brief overview of what the current comparative and fossil evidence informs us about the evolutionary history of the hominin hand. When discussing hominin traits, and what they allow us to know it relates Rather than being the exclusive site of muscle insertion, these phalangeal fossae are simply the depressed areas along the sides of a longitudinal palmar median bar. However, recent evidence suggests that for closely related species (and individuals within a species), absolute brain size is arguably a better predictor of cognitive ability than relative brain size, as the latter introduces errors [62,63]. This working hypothesis is then used to evaluate the available fossil and comparative evidence in the context of when, where, and possibly why (i.e. Brain size, cranial morphology, climate, and time machines, Hominid cranial capacity versus time: a regression approach, Hominid brain size versus time: revised regression estimates, Gradual, autocatalytic and punctuational models of hominid brain evolution: a cautionary tale, A draft sequence of the Neandertal genome. official website and that any information you provide is encrypted Sarmiento EE. Additionally, technologies and innovations appear and then disappear at individual sites [83], suggesting that either cultural behaviours are lost within populations or site occupancy is ephemeral. He argues that this is the result of a high mortality rate in subadults caused by environmental stress resulting from the changing environment during the Plio-Pleistocene. While there is a great deal of evidence pointing to H. sapiens migrating to the Americas by about 1413.3 kya, the oldest firm evidence places the arrival of H. sapiens in the southwestern United States by 2321 kya. positive slope for the regression of brain size against time), but there should be no systematic difference in mean residual CC between time periods. Increased mortality, however, could also result from increased predation pressure. However, within Eurasia, there was further evidence of encephalization within H. erectus ( = 0.08, t = 4.57, p < 0.001) and H. neanderthalensis ( = 0.46, t = 2.67, p = 0.01), but not within H. heidelbergensis nor within H. sapiens. afarensis(Leakey et al. 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. However, we do not know how much of an issue predation pressure was for early Homo. Further evidence for small-bodied hominins from the Late Pleistocene of Flores, Indonesia. Tuttle RH. Brief communication: Plio-Pleistocene eagle predation on fossil cercopithecids from the Humpata Plateau, southern Angola, Early hominid evolution and ecological change through the African Plio-Pleistocene, Chimpanzee and felid diet composition is influenced by prey brain size, Large body and small brain and group sizes are associated with predator preferences for mammalian prey. Relating to when you said by having fossilized skeletal remains of early humans allows us to have a better idea of how things were at this time, Lucy particularly helped with this. autapomorphic) at some point along their respective lineages. As such, we briefly discuss these uncertainties and the impact they have on the specific hand features which we infer were present in the Pan-Homo LCA. This is the origin of the genus Homo. As with other aspects of hominin sociality, language does not fossilize; instead we have to infer the evolutionary changes in the complexity of language ability from archaeological and fossil evidence. 1999b). Some of these adaptations could also be linked to the step-increase in brain size between H. habilis and H. erectus/ergaster [1,3]. In: Isaac GL, McKown ER, editors. Ruff C. B., Trinkaus E., Holliday T. W. 8) (Jacofsky, 2003). Tobias [74] identified a marked difference in the demography of hominin assemblages between the late australopithecines and early Homo. One of the most distinct features of recent human evolution is the trend towards increasingly large brains over the Plio-Pleistocene. If such conditions can be directly identified or indirectly inferred, then there is a working hypothesis regarding the primitive (or ancestral) conditions within the evolutionary lineage under study. The recovered proximal phalanges are relatively straight (Lorenzo et al. Correlations between absolute brain size and residual brain size (size controlled for time) and environmental variables, both over all hominins and within lineages. 2000. [see Constantino & Wood, 2007]), Homo floresiensis, Homo erectus sensu lato, Homo antecessor, Homo neanderthalensis, and Homo sapiens. Wood B, Richmond BG. adapted to our environment over time. In this model, unity of the species was maintained by periodic interbreeding across wide areas. The hands of these hominins are likely derived from the condition in the Pan-Homo LCA (and Au. Lorenzo C, Arsuaga JL, Carretero JM. Bold type highlights results consistent with environmental hypotheses. Lorenzo et al. Relative brain size and basal metabolic rate in terrestrial vertebrates, A hypothesis to explain the role of meat-eating in human evolution, On diet, energy metabolism, and brain size in human evolution. africanus, and inferred in the LCA at Node 7 (Fig. However, parsimony as well as many phenetic similarities between the hands of modern humans and African apes (rather than Asian apes) suggests it is more likely that the hand of the Pan-Homo LCA resembled that of an African ape (Corruccini, 1978; Begun, 1992, 2004; Richmond et al. This cost is even higher in later hominin species; resting metabolic rate of female Homo ergaster was an estimated 1.53 times higher than that of Australopithecus afarensis and is 1.64 times higher for female Homo sapiens [3]. This would enable inferences about how the mechanics of particular muscles have become derived compared with their function in the Pan-Homo LCA. Evolutionary reasoning demands that individuals can afford to pay hefty costs only if they are outweighed by commensurate benefits. An extended juvenile period allows for a protracted learning period [76,77], during which sophisticated reasoning and problem-solving capabilities have the opportunity to develop. The first clearly visible changes are present in Au. However, this debate involves the functional interpretation of the reconstructed LCA morphology, which logically follows the establishment of the character states in question. Napier JR. Fossil hand bones from Olduvai Gorge. Despite the controversy over the taxonomic attribution of the Swartkrans specimens, they both suggest that the derived condition of the DI1 had evolved in the hominin clade by at least 1.5 Ma with the hypothetical ancestor (Fig. 's (1999) description suggests that the styloid process seen in modern humans and Neandertals evolved either after the LCA shared with H. antecessor, or has evolved independently in both lineages. The recent discovery of a hominin species on the Indonesian island of Flores adds significantly to our knowledge of early hominin wrist morphology despite the fact that this material dates to only 0.018 Ma (Brown et al. Corruccini RS. . The terminal thumb phalanx of, Green DJ, Gordon AD. Terrestrial traits in the hands and feet of gorillas. These analyses strongly suggest that there is a combination of processes driving hominin brain evolution. Using both absolute and residual brain size estimates, we show that hominin brain evolution was likely to be the result of a mix of processes; punctuated changes at approximately 100 kya, 1 Mya and 1.8 Mya are supplemented by gradual within-lineage changes in Homo erectus and Homo sapiens sensu lato. Marzke MW, Marzke RF. Joint function and grips of the. For example, the condition at Node 2 could be the same as is present in modern humans; it could be the same as is present in extant great apes or it could even be the same as is present in non-hominid primates. 2004. It is also highly probable that hand features shared by Pongo and the African apes but not with non-hominids were also present in the hands of the LCAs for Hominidae and Homininae as well as the Pan-Homo LCA (Fig. 7C). Trinkaus E, Churchill SE, Villemeur I, Riley KG, Heller JA, Ruff CB. Thus, at the present time, there are no independent methods which can explicitly estimate changes in social group size or population density in hominins over time. Gommery & Senut (2006) suggest that the distal thumb phalanx of Orrorin has an expanded apical tuft (Table 1, d), which represents a derived condition relative to that inferred for the Pan-Homo LCA. Also, I like that you mentioned that these remains of our ancestors allowed us to see the route evolution took to get us where we are today. In modern humans (bottom), the DI1 pollical insertion is more extensive along the medial aspect of the first metacarpal shaft that often leaves a clear muscle-marking on the bone. 1991; Niewoehner et al. Both of these species of Homo are derived in all of the features listed in Table 1(except f and p, for which they retain the condition that is inferred for the Pan-Homo LCA) in comparison with the Pan-Homo LCA. The middle of the face protrudes, the teeth are set forward, the enlarged cheekbones sweep backward, and the nasal passages are voluminous. Wood BA. Two first metacarpals and one third metacarpal provide additional information. However, this facet pattern is well-documented in modern humans (Lewis, 1989: p. 81, Fig. There are over 20 hand fossils from Swartkrans (Susman, 1988b). (1999) noted that this capitate also displays a small, dorsally placed articulation for the trapezoid and concluded that ATD6-24 is the most ancient fossil with a morphology of the trapezoid facet transitional between Australopithecus and later Homo (Lorenzo et al. Ch 19 Flashcards | Quizlet 1998. In particular, modern humans are unique among hominids in having a distinct muscle belly for the FPL that is separate from that of the flexor digitorum profundus (FDP). Pickering T. R., Clarke R. J., Moggi-Cecchi J. 2003). Instead, hominid evolution produced a dense thicket of branches, with several species co-existing at any given time except for the last 30,000 years or so. 1Human Origins Program, Department of Anthropology, National Museum of Natural History, Smithsonian Institution, Washington DC, USA, 2School of Human Evolution and Social Change, Arizona State University, Tempe, AZ, USA, 3Institute of Human Origins, Arizona State University, Tempe, AZ, USA, 4The CORE Institute, Center for Orthopedic Research and Education, Sun City West, AZ, USA. The oblique head of adductor pollicis (APo) also showing a tendon to the distal phalanx along the ulnar margin that also functioned to flex the distal phalanx. 2.5-million-year-old stone tools from Gona, Ethiopia. Hominin traits are a representation of a Instead, they advocate that discrete archaic populations of Homo evolved locally in Africa, Asia, and Europe. Tocheri MW. Buchsbaum D., Bridgers S., Weisberg D. S., Gopnik A. Neanderthal hands in their proper perspective. The raw and the stolen: cooking and the ecology of human origins, The ecology of social transitions in human evolution, Punctuated equilibria: the tempo and mode of evolution reconsidered. However, if Neanderthals are viewed as a continuum from H. heidelbergensis [66,67], there is evidence for encephalization within this lineage, but not for a considerable period after colonizing Eurasia. 2007a,b). The "Robust" Australopiths | Learn Science at Scitable - Nature The pollical attachment of the first dorsal interosseous muscle (DI1) may provide a less ambiguous skeletal character (Jacofsky, 2003). Tocheri MW, Razdan A, Williams RC, Marzke MW. 333-15, A.L. The reasons for this are twofold. afarensis(Bush et al. Tocheri MW, Jungers WL, Larson SG, et al. Hand and foot remains from the Gran Dolina Early Pleistocene site (Sierra de Atapuerca, Spain). 1982; Ward et al. down food as we do. Origin of human bipedalism as an adaptation for locomotion on flexible branches. 1999; Drapeau et al. The cladogram shown in Fig. The 18O records provide an estimate of global climatic conditions, whereas the dust records provide a climate record for Africa and Arabia. We then combine the evidence from the hominin fossil record with the comparative evidence from modern humans and great apes to reassess our inferences regarding the hand of the Pan-Homo LCA. Apart from dietary changes, an intriguing possibility is that the use of fire for cooking made food more digestible [45], which became increasingly important as hominins expanded their range into more temperate zones [46]. afarensis represent the primitive state for all later hominins, then we should expect to see a similar pattern of morphology in hominins from the Late Pliocene and Early Pleistocene, albeit with the possibility of exhibiting derived modifications in their hand structure. Marzke MW, Marzke RF, Linscheid RL, et al. ihk R. Ontogenesis of the skeleton and intrinsic muscles of the human hand and foot. Brain size change at approximately 100 kya is coincident with demographic change and the appearance of fully modern language. africanus (Tocheri, 2007; David Green, personal communication). A 3D quantitative comparison of trapezium and trapezoid relative articular and nonarticular surface areas in modern humans and great apes. Goren-Inbar N., Alperson N., Kislev M. E., Simchoni O., Melamed Y., Ben-Nun A., Werker E. Niewoehner WA. Firstly, we evaluate the temporal change over all hominins; we then divide the groups into four super-species (Australopithecus spp., Homo habilis, H. erectus (including both H. erectus and H. ergaster) and H. sapiens (H. sapiens, H. heidelbergensis and Homo neanderthalensis); finally, we break down the H. sapiens group into anatomically modern humans (AMHs), Neanderthals and H. heidelbergensis. As additional hand fossils are recovered from other hominins that predate 2.5 Ma, they should also show the primitive conditions for these 13 features, unless they (or Australopithecus) have become uniquely derived (i.e. 1995; Marzke, 1997; Panger et al. africanus (TM 1526) no longer exhibit a radio-ulnarly oriented articulation for the base of the second metacarpal (Lewis, 1973; Marzke, 1983; McHenry, 1983; Ward et al. The necessity of such research is underscored by the mesenchymal formation of the osteological and myological structures of the hand during embryogenesis (ihk, 1972). New hominid fossils from the Swartkrans Formation (19791986 excavations): postcranial specimens. Language increases an individual's understanding of the world because the individual is no longer limited to holding only information that it directly perceives [34]. Since our ancestors were hunters and gathers, they did a lot of walking In comparison with the inferred morphology of the Pan-Homo LCA, the Australopithecus hand exhibits derived features. 8) (Swindler & Wood, 1973; Jacofsky, 2003). Le Gros Clark WE. The brain size evidence suggests that the most recent period of brain size increase is around 100 kya (figure 1a,b). indet. Most tantalizing and enigmatic is the role of social evolution in the encephalization process. Second, it was recovered in direct association with cranio-dental and additional postcranial material (Brown et al. Visual representation of the derived morphological features in the hands of modern humans and Neandertals (the lowercase letters correspond with list in Table 1). 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. Primate molecular divergence dates. Two views of the origin of man. 7C). Shultz S., Noe R., McGraw W. S., Dunbar R. I. Adductor pollicis (oblique and transverse heads), The derived mechanics of this muscle may be identifiable based on carpal geometry, but more research is required (see. 7A,B). 2007), it is unclear whether they characterized the Homininae LCA as well (Fig. Thus, here we focus primarily on identifying the pattern of derived features that modern human and Neandertal hands share relative to earlier hominins and the Pan-Homo LCA such that the morphology of their LCA can be reasonably inferred. In chimpanzees (top), the DI1 pollical insertion is localized to the proximo-medial base of the first metacarpal and the dorso-medial aspect of the trapezium. Using such a cladogram, it is reasonable to infer that modern human hand morphology predates the hypothetical split at Node 2 (e.g. I agree that by learning about these traits it truly shows how much we have evolved. Tocheri MW, Marzke MW, Liu D, et al. the study of evolution and understanding where we come from, and how we have 2). D. E . The power of possibility: causal learning, counterfactual reasoning, and pretend play, Social pressures have selected for an extended juvenile period in primates. Evidence that social group size changed in steps concurrently with brain size changes would more conclusively support the social brain hypothesis. In: Luckett WP, Szalay FS, editors. Thumbs, tools and early humans. Earliest humans in Europe: the age of TD6 Gran Dolina, Atupuerca, Spain. Speciation appears to be the key to change in Africa, whereas step changes associated with migration followed by within lineage encephalization are more characteristic of the Eurasian lineages. Biomechanics of phalangeal curvature. afarensis, Au. Because the FDP muscle is not well differentiated in baboons, independent digital control of distal phalangeal flexion is unlikely. 2003; Tocheri, 2007). Although its relationships to other hominin taxa remain a topic of lively debate, there is little doubt that the morphology of its partially preserved wrist is remarkably primitive (Tocheri et al. 2002, 2004; Wimmer et al. 1998). 2008, this volume; as well as Tuttle, 1967, 1969a,b; Jenkins & Fleagle, 1975; Richmond & Strait, 2000; Richmond et al. 2007), then it must be reasonably explained why modern humans and African apes share prenatal scaphoid-centrale fusion when orangutans and other arboreal suspensory non-hominid primates do not (Fig. HHS Vulnerability Disclosure, Help 2001; Orr, 2005; Tocheri, 2007). Two sources of climatic data were employed: global sea level predicted from benthic marine oxygen isotope (18O) records [69] and records of aeolian dust variability (terrigenous sediment) extracted from marine sediment cores off the East African coast [70]. This reorganization is best seen in modern humans and Neandertals, but there is also evidence of it in the H. antecessor capitate. This paper will (i) review the arguments for the pressures driving hominin brain expansion, (ii) quantitatively evaluate tempo changes in hominin brain size, and (iii) test environmentally based hypotheses for brain size change. Bipedalism started to emerge around 3 to 4 million years before enlarged brains did. africanus no longer exhibits the primitive radio-ulnar orientation (Marzke, 1983, 1997; Tocheri et al. The final step change in brain size that begins at approximately 100 kya may reflect this final phase shift in language complexity. Such features are probably homoiologies. Earliest evidence of modern human life history in North African early, The social brain: a project for integrating primate behavior and neurophysiology in a new domain. Additionally, the difficulty in estimating body sizes for hominins and the potential for introducing additional errors justifies the use of absolute brain size [50,54,64,65]. Language, gesture, skill: the coevolutionary foundations of language. Sister grouping of chimpanzees and humans as revealed by genome-wide phylogenetic analysis of brain gene expression profiles. The triquetrum has been briefly described but more thorough comparative descriptions or analyses of hominid triquetrum morphology are needed to evaluate this specimen's morphological affinities (Susman, 1988b). (2002) remind us that 2.52.6 Ma is the earliest that stone tools are visible as an archaeological record of behavior; stone tools may well have been made prior to 2.52.6 Ma, but the intensity with which they were made and used may not have been sufficient to leave an archaeological signal (Potts, 1991; Panger et al. The hand of the Pan-Homo LCA (Figs 2, ,4,4, Node 4) most likely resembled that of an extant African ape overall, or at the very least it likely shared most, if not all, of the characteristics that are symplesiomorphic among the extant great apes (all except f because it is shared only among African apes and modern humans) (Fig.

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