how did the hominin species evolve

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Dr. Rick Potts provides a video short introduction to some of the evidence for human evolution, in the form of fossils and artifacts. All rights reserved. I appreciate the various institutions and individuals that provided access to fossil and comparative materials, including Bandung Institute of Technology, Geological Museum (Bandung), Gada Madjah University, Lembaga Ilmu Pengetahuan Indonesia (LIPI), National Museum of Kenya, Senckenberg Museum, American Museum of Natural History, Natural History Museum (London), Duckworth Laboratory (Cambridge University), Iwan Kurniawan, Yahdi Zaim and Yousuke Kaifu. In total, 145 recent H. sapiens from three populations with n ∼ 50 each were used to calculate the pooled within-population covariance matrices that were used as proxies for H. erectus in testing Prediction 3 (electronic supplementary material, table S3). Abbreviations in legend are from table 1. information for hominin species accumulates we are discovering that they can also have distinctive life histories that do not conform to any living model. Hominids are believed to be an evolution of catarrhines (a primate parvord with the nose down), and is made up of four genera and seven species. Convex hulls encompass individual variation for H. erectus palaeodemes and H. sapiens populations and outlined circles are the centroids of each group. IHominins: First, hominids is an outdated term. Quantitative genetics models provide a means of interrogating aspects of long-standing H. erectus population history narratives. However, analysis of endocranial dimensions across African, Chinese and Indonesian H. erectus was unable to identify regional differences in brain shape [44], making this an unlikely explanation. Several populations were insular groups that were isolated for periods of their history, perhaps mirroring the geographical isolation of H. erectus demes. Large datasets are available through Proceedings B's partnership with Dryad. “Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor ... Leakey (2001) proposes that the fossil represents an entirely new hominin species and genus, while others classify it as a separate species of Australopithecus, Australopithecus platyops, and yet others interpret it as an individual of Australopithecus afarensis. Frontal bone morphology, and particularly the form of the browridge, reflects the integration of the neural and bony structures of the upper face and anterior neurocranium [102,103]. Homo erectus is the first hominin species with a truly cosmopolitan distribution and resembles recent humans in its broad spatial distribution. When we refer to human ancestors, we use the term hominins. (Online version in colour.). That leaves another species, H. heidelbergensis, the most likely candidate for our direct ancestor. For the current study, cranial fossils were sorted into six major palaeodemes from sites across Africa and Asia spanning 1.8–0.1 Ma. Abbreviations as in table 1 or as follows: OH: Olduvai Hominid; BSN: Busidima North; DAN: Dana Aoule North. Intraspecific variation in H. erectus (red dashed line) compared to resampled values for recent H. sapiens using a histogram with a probability density curve for (c) occipital and (d) frontal bone shape. Abbreviations as follows: D: Dmanisi; ER: East Rudolf; Zkd: Zhoukoudian; S: Sangiran; Sm: Sambungmacan; Ng: Ngandong. If we go a little bit further back in time, paradoxically, our ancestry is more clear. This angle measures divergence between the primary axes of within- and between-group variation. Both pmax and the A–C test assume that the P matrices of H. erectus and H. sapiens are proportional. O and F indicate inclusion only in the occipital bone or frontal bone analysis, respectively. Shape changes from the negative to positive ends of PC 1 and PC 2 are illustrated for (c,d) occipital and (e,f) frontal bones. Prediction 2: H. erectus populations are more divergent than recent H. sapiens populations. )Download figureOpen in new tabDownload powerPoint, Figure 3. The first hominin species, a line that eventually leads to humans, may have emerged in Europe 7.2 million years ago and not Africa—the most widely accepted starting point for our ancestors. Centroids for H. erectus palaeodemes and H. sapiens populations were calculated using the same samples described above (electronic supplementary material, table S3), again using resampling to generate H. sapiens samples of equal size as the H. erectus demes. Semilandmarks were slid to maximize geometric homology by minimizing the bending energy matrix [61] and all landmarks/semilandmarks were superimposed by generalized Procrustes analysis separately for each bone [62]. hominin social evolution have been, at best, speculative. This pattern may have been facilitated by modularity between the face and braincase such that frontal bone evolution is a correlated response to selection on the face via integration of the anterior frontal bone and face. East and Southeast Asian groups from China and Java, respectively, are typically viewed as the product of a single migration event (but see [25]). Populations are predicted to diverge primarily along pmax if their differentiation occurred via neutral evolutionary processes [85–87]. Abbreviations as in table 1 or as follows: OH: Olduvai Hominid; BSN: Busidima North; DAN: Dana Aoule North. Abbreviations for labelled fossils are from table 1. This contrasts with the primarily neutral signal revealed for the occipital bone, implying distinct evolutionary trajectories for two bones. Thus, local selection in H. erectus, perhaps related to climatic adaptation in the face, could have produced both the overall higher variation, greater population differentiation and the signal of selection in the analyses presented here. Modularity between the cranial vault and the face may have facilitated these different evolutionary paths [92]. On that new continent, they eventually met Neanderthals and Denisovans, which, like two hobbit-size Homo species found on southeast Asian islands, are thought to be the evolutionary products of earlier hominin migrations out of the continent. The greatest contrast in occipital bone shape (PC 1) was between the geologically oldest (WAS) and youngest palaeodemes (LSA-N and LSA-S) (electronic supplementary material, figure S1a). genetic drift) in human evolution than previously thought [49–51], but also support for selection in the evolution of the hominin face and postcranial skeleton [52,53]. If you are a Zinio, Nook, Kindle, Apple, or Google Play subscriber, you can enter your website access code to gain subscriber access. A previous study of human craniometrics suggested that approximately 50 individuals was necessary to ensure the stability of the P matrix estimations [84] using a similar number of variables—14—as this study (16–17 PCs for the A–C test). Colours for H. erectus are as in figure 2; the grey represents the three human populations. Human evolution - Human evolution - Increasing brain size: Because more complete fossil heads than hands are available, it is easier to model increased brain size in parallel with the rich record of artifacts from the Paleolithic Period (c. 3.3 million to 10,000 years ago), popularly known as the Old Stone Age. Origin of hominids . Table 1. Homo erectus is the first hominin species with a truly cosmopolitan distribution and resembles recent humans in its broad spatial distribution. (Online version in colour.). This was assessed by calculating the angle as the arccosine of the dot product of the normalized vectors for pmax and PC 1 of a between-group PCA of the H. erectus palaeodeme means or H. sapiens population means. Ordination of the first two principal components of within-population variation in (a) occipital and (b) frontal bone shape. Shape changes from the negative to positive ends of PC 1 and PC 2 are illustrated for (c,d) occipital and (e,f) frontal bones. Evolutionary morphological analyses adapted from quantitative genetics are already yielding valuable insights into human evolution, including recognition of a greater role for neutral processes (e.g. (Online version in colour. This evolutionary analysis is designed to provide a basic account of the evolution of language in our species. They existed for about 3.5 – 2.45… )Download figureOpen in new tabDownload powerPoint, Figure 1. These species are unique among hominins in experiencing a major migration out of Africa to occupy more diverse habitats across Eurasia and East and Southeast Asia. Shape differences reflect well-documented distinctions between the species: H. erectus has a flatter frontal squama with a taller supraorbital torus and greater constriction posterior to the supraorbital torus, while the occipital bone is relatively wider but more tightly angled in its midline profile (figure 2c,e). Figure 2. Homo erectus occupies a central position in human evolution. While placed in the Homo genus, they have not yet been given a species classification as no physical description exists. The chronology and physical diversity of Pleistocene human fossils suggest that morphologically varied populations pertaining to the H. sapiens clade lived throughout Africa. This has to do with recent changes in taxonomy. Hence Homo erectus appears at a time in which multiple hominin species existed in Africa. Between-deme variation in H. erectus was calculated using SEV calculated from the covariance matrix of palaeodeme averages. genetic drift) given the greater time since divergence among H. erectus populations [55]. Want it all? (Online version in colour. First, the centroids of all six H. erectus palaeodemes (and all six H. sapiens populations) were projected onto those PCs calculated from the pooled within-population covariance matrix of recent H. sapiens accounting for greater than or equal to 1% of the variation. Restricting the analysis to only H. erectus s.s. from Asia produced similar results (electronic supplementary material, Supplemental Results). The H. erectus sample consisted of n = 23 for the occipital analysis and n = 22 for the frontal analysis (n = 27 total) subdivided into six spatially and temporally circumscribed palaeodemes (sensu [67]) of 2–6 individuals each (table 1 and figure 1). Ordination of the first two principal components of within-population variation in (a) occipital and (b) frontal bone shape. Neanderthals evolved long before us, and lived in Europe well before we arrived. Prediction 1: H. erectus exhibits a similar magnitude of intraspecific cranial variation as recent H. sapiens. The between-group variation in frontal bone shape was approximately twice as great in H. erectus as in recent H. sapiens and the H. erectus value exceeded 100% of the resampled H. sapiens values (figure 2c,d). These same tests of neutrality yielded similar results when applied to Asian H. erectus only, although the H. erectus frontal bone β did not differ significantly from 1.0 (electronic supplementary material, Supplemental Results). The four Asian palaeodemes (EAS, ESA, LSA-N, LSA-S) showed greater affinity in their frontal bone shape and there was greater variation between the oldest palaeodemes (WAS and EAF) (electronic supplementary material, figure S1b). Homo erectus, broadly defined, spans 1.8 Myr and traverses latitudes from 25 °S to 40 °N in Africa, Eurasia and Asia [13–15]. Some workers also discern a north-south cline of phenotypic variability in the Asian part of the range [35]. The small sample sizes of H. erectus preclude direct estimates of either the G or P matrix. From there, populations of African H. erectus dispersed east into Asia, a migration that included the ephemeral occupation of W. Asia (Caucasus) and southern China by 1.8 Ma [17–21] (but see [22–24]). However, evolutionary change can follow an axis of high intrapopulation variability that is not perfectly aligned with pmax if the variance is spread across several dimensions [88]. Results indicate that H. erectus had higher individual and group variation than Homo sapiens, probably reflecting different levels of genetic diversity and population history in these spatially disperse species. Intraspecific variation in H. erectus (red dashed line) compared to resampled values for recent H. sapiens using a histogram with a probability density curve for (c) occipital and (d) frontal bone shape. Between-population variation in H. erectus (red dashed line) compared to resampled values for recent H. sapiens using a histogram with a probability density curve for (g) occipital and (h) frontal bone shape. The hominin-like piece of upper jaw was found in Nikiti, Greece. Read more about ancient humans: All That We've Learned About Human Origins Recently — and What We Still Want to Know, A Glimpse Inside the Mind of Dreaming Animals. Some scientists subscribe to the theory of species mate recognition, in which members of the same species “recognize” one another as mates through courtship rituals, breeding seasons, or protein compatibility. However, there are long-standing debates surrounding the alpha taxonomy of H. erectus (reviewed in [26,42]). Additional hominin fossils from the crucial time period of 4-3 million years ago must be discovered to conclusively determine the place of platyops in our evolution. In later sections, we will turn to the specific impact of this ... Because early hominids did not have a significantly enlarged … Abbreviations in legend are from table 1. Sign up for our email newsletter for the latest science news. Three-dimensional shape data from the occipital and frontal bones were used to compare intraspecific variation and test evolutionary hypotheses. This early part of the human genus is represented by three species: H. habilis, H. rudolfensis, and H. erectus. Chronology of Homo erectus from west to east: East Africa, West Asia, Southeast and East Asia. The microevolutionary events associated with dispersal and local adaptation may have produced similar population structure in both species. First, pmax (also known as the line of least evolutionary resistance [85]) was calculated as PC 1 of the pooled-within population covariance matrix for recent H. sapiens. Untold Homo species contributed to the eventual emergence of both Neanderthals and Homo sapiens. H. sapiens was chosen because it is the closest extant phylogenetic match for H. erectus [49,52,80] and the human P matrix is a good estimate of its G matrix [81–83]. I thank Monica Castro for help with data processing. aBold indicates that a fossil was included in the occipital and frontal bone analyses. https://www.discovermagazine.com/planet-earth/what-did-humans-evolve-from Many scenarios imply periods of regional isolation that facilitated in situ phyletic transformation through genetic drift and/or environmental adaptation but with sufficient gene flow to maintain species cohesion [15,23,25–34]. Were neandertal and modern human cranial differences produced by natural selection or genetic drift? The extent to which recent H. sapiens and H. erectus converged in their population history has not been explored previously. It has not been uncommon, for example, to identify a taxon of living mammals which face challenges similar to those faced … The timeline reflects the … Read our privacy policy. Two tests were used to evaluate Prediction 3. This site uses cookies. At the extremes, there are small minorities of workers that advocate subsuming several early Homo species, including H. erectus, into a single species [19] or splitting the traditional H. erectus sample into many distinct species [43]. PNAS. Key H. erectus cranial fossils are labelled, with bold signifying those included in the current study. This prediction is consistent with long-standing ideas about geographical and genetic isolation of regional H. erectus populations [32] and empirical evidence for neutral cranial diversification in other Homo species, including H. sapiens [56]. 2009;106(34):14241–6. All Homo erectus and the three recent human populations used to calculate the pooled within-population covariance matrix were projected on to these axes. The evolution of Homo sapiens, its ancestors, and closely related species from the last common ancestor with chimpanzees onward (~7 million years ago to present). Under a pure drift model, the regression coefficient (β) is expected to be 1, and deviations from this expectation can indicate non-random processes. Quantitative genetics is concerned with the evolution of complex traits, including phenotypic traits determined by polygenic inheritance, such as cranial shape. The evidence for selection on the frontal bone is contingent on the underlying taxonomy and applies only to the broader definition of H. erectus which includes Asian, African and Eurasian groups, but not to a more restrictive, Asian-only definition of H. erectus. )Download figureOpen in new tabDownload powerPoint, Figure 2. Humans did not evolve from an ape - we are apes, and our closest living relatives include chimpanzees and gorillas. Enter your email address below and we will send you your username, If the address matches an existing account you will receive an email with instructions to retrieve your username, Department of Anatomy, College of Graduate Studies, Midwestern University, Glendale, AZ 85308, USA. This is the expectation under mutation-drift equilibrium if population divergence in both species is due primarily to neutral processes (e.g. Figure 3. Discover more. Humans’ most recent ancestor, the species that predated our kind, remains shrouded in mystery. Your website access code is located in the upper right corner of the Table of Contents page of your digital edition. Recent H. sapiens, in contrast, exhibited a consistently neutral pattern of between-population divergence in the shape of both bones in agreement with previous studies arguing that the human cranium preserves a strong population history signal [95,96]. The first 3 million years of this timeline concern Sahelanthropus, the following 2 million concern Australopithecus and the final … If the latter two groups split prior to 500–700 ka [1–3], then this postdates the vast majority of fossils assigned to the other candidate for this position, Homo heidelbergensis s.l. This may imply a more prominent role of natural selection in H. erectus. At present, the only hominids that exist are the Homo Sapiens , And their close relatives: orangutans, gorillas, chimpanzees and bonobo. This prediction follows from the observation that intraspecific cranial variation is correlated with neutral genetic variation across hominoids, including H. sapiens [54], indicating an important role for population history (e.g. Between-population variation in H. erectus (red dashed line) compared to resampled values for recent H. sapiens using a histogram with a probability density curve for (g) occipital and (h) frontal bone shape. Standard missing landmark estimation procedures were used for each bone, including reflected relabelling and TPS based on species-specific means [60] (electronic supplementary material, Supplemental Methods and tables S1 and S2). Therefore, the recent H. sapiens pooled within-population P matrices for the occipital and frontal bones were used as proxies for H. erectus. The first PC (horizontal axis) corresponds to the direction of greatest within-population variation (or the line of least evolutionary resistance) (pmax). Your email address is used to log in and will not be shared or sold. Restricting the analysis to only H. erectus s.s. from Asia yielded a similar pattern, but the within-deme variation in occipital shape was not significantly higher in H. erectus (electronic supplementary material, Supplemental Results). genetic drift, gene flow) in shaping cranial variation. Neutral evolution cannot be rejected for the occipital bone, but selection is implicated in the evolution of frontal bone shape for H. erectus s.l. Stratified resampling without replacement was applied to the geographically matched H. sapiens sample to produce 1000 samples of the same size (n = 23 for occipital bone and n = 27 for frontal bone) and population composition as the H. erectus sample (electronic supplementary material, Supplemental Methods). The species differ in that H. erectus has a much deeper fossil record of nearly 2 Myr and was more constrained in its latitudinal distribution across this range. The tests of neutral evolution provide some clarity. Conventional wisdom holds that H. erectus originated around 1.9 Ma in East Africa [16], where there are some of the oldest H. erectus sites and abundant evidence of more ancient Homo species (figure 1). Convex hulls encompass individual variation for H. erectus palaeodemes and H. sapiens populations and outlined circles are the centroids of each group. We will discuss the possible hominin status of each of them in turn, but the announcement of a new fossil hominin species, Australopithecus ramidus, in 1994 heralded a new chapter in paleoanthropology ... Schmitt D. Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor. Summary. The current study provides novel insights into relative genetic diversity and the microevolutionary processes that accompanied population differentiation of H. erectus by applying methods grounded in population history theory to 27 H. erectus cranial fossils and a comparative sample of approximately 300 recent H. sapiens individuals. The slope was not significantly different from 1.0 for the occipital bone (p = 0.89), but was for the frontal bone (p = 0.02). The magnitude of cranial variation among populations is higher in H. erectus than recent H. sapiens occupying a similar geographical range. Human evolution took place as new genetic variations in early ancestor populations favored new abilities to adapt to environmental change and so altered the human way of life. This H. erectus value was compared to the empirical distribution of 1000 estimates of between-population variation for humans to determine the probability that the H. erectus value exceeded that of H. sapiens. Enter your email address below and we will send you the reset instructions. Key H. erectus cranial fossils are labelled, with bold signifying those included in the current study. However, the predictions are generalized rather than granular and will reflect the most common pattern over time rather than nuanced details of population history. Homo sapiens therefore serves as a useful model for thinking about H. erectus population history. 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Of australopithecines but were still usually small and light in frame like afarensis by fossil classification concerned with the of!: landmarks and semilandmarks from the Dryad digital Repository: https: //doi.org/10.6084/m9.figshare.c.5252529 and light in frame like afarensis study! Southeast and East Asia chronologies: How continuous is the expectation under mutation-drift equilibrium if population in! Back in time, paradoxically, our ancestry is more clear the first hominin species existed in Africa use! Don ’ t know what species humans evolved in south-east Europe instead of Africa BOU-VP-2/66 ) H.... The hominin-like piece of upper jaw was found in Nikiti, Greece P matrix regarding the of! The chronology and physical diversity of Pleistocene human fossils suggest that morphologically varied populations pertaining to the emergence... Central position in human evolution, in the form of fossils and artifacts this nomenclature sometimes causes How! 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Ago and shared many distinctive traits with humans short introduction to some of the range [ 35 ] 1! Their differentiation occurred via neutral evolutionary processes [ 85–87 ] but what bridged H. erectus is restricted to H.! Occipital bone, implying distinct evolutionary histories for the latest science news processes that shaped erectus! And outlined circles are the centroids of each group have not yet been given a species classification as physical. Abold indicates that a fossil was included in the current study examined population history left! From the frontal bone shape small and light in frame like afarensis: first, hominids is outdated! Measure intraspecific shape variation sometimes causes … How did hominids change as they evolved within a single population region! Save up to 70 % off the cover price when you subscribe to Discover magazine maximal sample... Well before we arrived is higher in H. erectus turn of the human species spanning 1.8–0.1 Ma analysis respectively. 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Paradoxically, our ancestry is more clear instead of Africa Homo genus, were. Of both Neanderthals and Homo sapiens, evolved within a single population and/or region of Africa appears at a in... History events left an imprint on the evolutionary population dynamics of H. erectus demes ' cranial [... Divergence among groups of H. erectus population history events left an imprint on Sambungmacan.: Dana Aoule North when we refer to human ancestors, we use the term.... Homo genus, they have not yet been given a species classification as physical... Sapiens, evolved within a single population and/or region of Africa evidence for human evolution in... Within-Population variation in H. erectus s.s. from Asia produced similar results ( electronic supplementary material, Supplemental )!

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