scholarly journals Unconstrained cranial evolution in Neandertals and modern humans compared to common chimpanzees

2015 ◽  
Vol 282 (1817) ◽  
pp. 20151519 ◽  
Author(s):  
Timothy D. Weaver ◽  
Chris B. Stringer
Keyword(s):  
Genetic Drift ◽  
Dna Sequences ◽  
Modern Human ◽  
Effective Population ◽  
Evolutionary Processes ◽  
Modern Humans ◽  
Developmental Constraints ◽  
Time Estimates ◽  
Cranial Measurements ◽  
Common Chimpanzee

A variety of lines of evidence support the idea that neutral evolutionary processes (genetic drift, mutation) have been important in generating cranial differences between Neandertals and modern humans. But how do Neandertals and modern humans compare with other species? And how do these comparisons illuminate the evolutionary processes underlying cranial diversification? To address these questions, we used 27 standard cranial measurements collected on 2524 recent modern humans, 20 Neandertals and 237 common chimpanzees to estimate split times between Neandertals and modern humans, and between Pan troglodytes verus and two other subspecies of common chimpanzee. Consistent with a neutral divergence, the Neandertal versus modern human split-time estimates based on cranial measurements are similar to those based on DNA sequences. By contrast, the common chimpanzee cranial estimates are much lower than DNA-sequence estimates. Apparently, cranial evolution has been unconstrained in Neandertals and modern humans compared with common chimpanzees. Based on these and additional analyses, it appears that cranial differentiation in common chimpanzees has been restricted by stabilizing natural selection. Alternatively, this restriction could be due to genetic and/or developmental constraints on the amount of within-group variance (relative to effective population size) available for genetic drift to act on.

scholarly journals Model-based detection and analysis of introgressed Neanderthal ancestry in modern humans

2017 ◽  
Author(s):  
Matthias Steinrücken ◽  
Jeffrey P. Spence ◽  
John A. Kamm ◽  
Emilia Wieczorek ◽  
Yun S. Song
Keyword(s):  
Genetic Material ◽  
Genetic Load ◽  
Modern Human ◽  
Human Populations ◽  
Effective Population ◽  
Weak Selection ◽  
Modern Humans ◽  
High Coverage ◽  
Model Based ◽  
And Migration

AbstractGenetic evidence has revealed that the ancestors of modern human populations outside of Africa and their hominin sister groups, notably the Neanderthals, exchanged genetic material in the past. The distribution of these introgressed sequence-tracts along modern-day human genomes provides insight into the ancient structure and migration patterns of these archaic populations. Furthermore, it facilitates studying the selective processes that lead to the accumulation or depletion of introgressed genetic variation. Recent studies have developed methods to localize these introgressed regions, reporting long regions that are depleted of Neanderthal introgression and enriched in genes, suggesting negative selection against the Neanderthal variants. On the other hand, enriched Neanderthal ancestry in hair- and skin-related genes suggests that some introgressed variants facilitated adaptation to new environments. Here, we present a model-based method called diCal-admix and apply it to detect tracts of Neanderthal introgression in modern humans. We demonstrate its efficiency and accuracy through extensive simulations. We use our method to detect introgressed regions in modern human individuals from the 1000 Genomes Project, using a high coverage genome from a Neanderthal individual from the Altai mountains as reference. Our introgression detection results and findings concerning their functional implications are largely concordant with previous studies, and are consistent with weak selection against Neanderthal ancestry. We find some evidence that selection against Neanderthal ancestry was due to higher genetic load in Neanderthals, resulting from small effective population size, rather than Dobzhansky-Müller incompatibilities. Finally, we investigate the role of the X-chromosome in the divergence between Neanderthals and modern humans.

scholarly journals The Role of Genetic Drift in Shaping Modern Human Cranial Evolution: A Test Using Microevolutionary Modeling

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Heather F. Smith
Keyword(s):  
Temporal Bone ◽  
Genetic Drift ◽  
Geographic Distance ◽  
Modern Human ◽  
Neutral Evolution ◽  
Modern Humans ◽  
Cranial Variation ◽  
History Of ◽  
Mandibular Morphology ◽  
And Migration

The means by which various microevolutionary processes have acted in the past to produce patterns of cranial variation that characterize modern humans is not thoroughly understood. Applying a microevolutionary framework, within- and among-population variance/covariance (V/CV) structure was compared for several functional and developmental modules of the skull across a worldwide sample of modern humans. V/CV patterns in the basicranium, temporal bone, and face are proportional within and among groups, which is consistent with a hypothesis of neutral evolution; however, mandibular morphology deviated from this pattern. Degree of intergroup similarity in facial, temporal bone, and mandibular morphology is significantly correlated with geographic distance; however, much of the variance remains unexplained. These findings provide insight into the evolutionary history of modern human cranial variation by identifying signatures of genetic drift, gene flow, and migration and set the stage for inferences regarding selective pressures that early humans encountered since their initial migrations around the world.

scholarly journals A View of Modern Human Origins from Y Chromosome Microsatellite Variation

1999 ◽  
Vol 9 (6) ◽  
pp. 558-567 ◽  
Author(s):  
Mark Seielstad ◽  
Endashaw Bekele ◽  
Muntaser Ibrahim ◽  
Amadou Touré ◽  
Mamadou Traoré
Keyword(s):  
Y Chromosome ◽  
Phylogenetic Trees ◽  
Distance Measure ◽  
Modern Human ◽  
African Origin ◽  
Effective Population ◽  
Modern Humans ◽  
Microsatellite Variation ◽  
Modern Human Origins ◽  
African Populations

The idea that all modern humans share a recent (within the last 150,000 years) African origin has been proposed and supported on the basis of three observations. Most genetic loci examined to date have (1) shown greater diversity in African populations than in others, (2) placed the first branch between African and all non-African populations in phylogenetic trees, and (3) indicated recent dates for either the molecular coalescence (with the exception of some autosomal and X-chromosomal loci) or for the time of separation between African and non-African populations. We analyze variation at 10 Y chromosome microsatellite loci that were typed in 506 males representing 49 populations and every inhabited continent and find significantly greater Y chromosome diversity in Africa than elsewhere, find the first branch in phylogenetic trees of the continental populations to fall between African and all non-African populations, and date this branching with the (δμ)2 distance measure to 5800–17,400 or 12,800–36,800 years BP depending on the mutation rate used. The magnitude of the excess Y chromosome diversity in African populations appears to result from a greater antiquity of African populations rather than a greater long-term effective population size. These observations are most consistent with a recent African origin for all modern humans.

scholarly journals The evolutionary history of Neandertal and Denisovan Y chromosomes

2020 ◽  
Author(s):  
Martin Petr ◽  
Mateja Hajdinjak ◽  
Qiaomei Fu ◽  
Elena Essel ◽  
Hélène Rougier ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Evolutionary History ◽  
Genetic Load ◽  
Modern Human ◽  
Gene Pools ◽  
Human History ◽  
Effective Population ◽  
Modern Humans ◽  
Y Chromosomes ◽  
History Of

AbstractAncient DNA has allowed the study of various aspects of human history in unprecedented detail. However, because the majority of archaic human specimens preserved well enough for genome sequencing have been female, comprehensive studies of Y chromosomes of Denisovans and Neandertals have not yet been possible. Here we present sequences of the first Denisovan Y chromosomes (Denisova 4 and Denisova 8), as well as the Y chromosomes of three late Neandertals (Spy 94a, Mezmaiskaya 2 and El Sidrón 1253). We find that the Denisovan Y chromosomes split around 700 thousand years ago (kya) from a lineage shared by Neandertal and modern human Y chromosomes, which diverged from each other around 370 kya. The phylogenetic relationships of archaic and modern human Y chromosomes therefore differ from population relationships inferred from their autosomal genomes, and mirror the relationships observed on the level of mitochondrial DNA. This provides strong evidence that gene flow from an early lineage related to modern humans resulted in the replacement of both the mitochondrial and Y chromosomal gene pools in late Neandertals. Although unlikely under neutrality, we show that this replacement is plausible if the low effective population size of Neandertals resulted in an increased genetic load in their Y chromosomes and mitochondrial DNA relative to modern humans.

scholarly journals Flexibility of co-evolutionary patterns in ectoparasite populations: genetic structure and diversity in Apodemus mice and their lice

2016 ◽  
Author(s):  
J. Martinů ◽  
V. Hypša ◽  
J. Štefka
Keyword(s):  
Genetic Diversity ◽  
Host Specificity ◽  
Dna Sequences ◽  
Effective Population ◽  
Evolutionary Processes ◽  
Specific Level ◽  
Genetic Diversity And Structure ◽  
Host Affiliation ◽  
Parasite Populations ◽  
The Impact

AbstractHost-parasite co-evolution belongs among the major processes governing evolution of biodiversity on the global scale. Numerous studies performed at inter-specific level revealed variety of patterns from strict co-speciation to lack of co-divergence and frequent host-switching, even in species tightly linked to their hosts. To explain these observations and formulate ecological hypotheses, we need to acquire better understanding to parasites’ population genetics and dynamics, and their main determinants. Here, we analyse the impact of co-evolutionary processes on genetic diversity and structure of parasite populations, using a model composed of the louse Polyplax serrata and its hosts, mice of the genus Apodemus, collected from several dozens of localities across Europe. We use mitochondrial DNA sequences and microsatellite data to describe the level of genealogical congruence between hosts and parasites and to assess genetic diversity of the populations. We also explore links between the genetic assignment of the parasite and its host affiliation, and test the prediction that populations of the parasite possessing narrower host specificity show deeper pattern of population structure and lower level of genetic diversity as a result of limited dispersal and smaller effective population size. We demonstrate an overall complexity of the co-evolutionary processes and their variability even among closely related lineages of the parasites. In the analysis of several sympatric parasite populations, we find strong evidence for the link between the width of host specificity and genetic diversity of parasites.

Clash of signs: Putting bilingualism back into language evolution

2020 ◽  
Author(s):  
Steven Samuel
Keyword(s):  
Language Evolution ◽  
Modern Human ◽  
Alarm Calls ◽  
Bilingual Children ◽  
Human Language ◽  
Typically Developing ◽  
Typically Developing Children ◽  
Modern Humans ◽  
The Real ◽  
Multiple Languages

Research and thinking into the cognitive aspects of language evolution has usually attempted to account for how the capacity for learning even one modern human language developed. Bilingualism has perhaps been thought of as something to think about only once the ‘real’ puzzle of monolingualism is solved, but this would assume in turn (and without evidence) that bilingualism evolved after monolingualism. All typically-developing children (and adults) are capable of learning multiple languages, and the majority of modern humans are at least bilingual. In this paper I ask whether by skipping bilingualism out of language evolution we have missed a trick. I propose that exposure to synonymous signs, such as food and alarm calls, are a necessary precondition for the abstracting away of sound from referent. In support of this possibility is evidence that modern day bilingual children are better at breaking this ‘word magic’ spell. More generally, language evolution should be viewed through the lens of bilingualism, as this is the end state we are attempting to explain.

scholarly journals A phylogenetic estimator of effective population size or mutation rate.

Genetics ◽  
1994 ◽  
Vol 136 (2) ◽  
pp. 685-692 ◽  
Author(s):  
Y X Fu
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Mutation Rate ◽  
Dna Sequences ◽  
High Efficiency ◽  
Minimum Variance ◽  
Population Subdivision ◽  
Effective Population ◽  
Fisher Model ◽  
Mitochondrial Sequences

Abstract A new estimator of the essential parameter theta = 4Ne mu from DNA polymorphism data is developed under the neutral Wright-Fisher model without recombination and population subdivision, where Ne is the effective population size and mu is the mutation rate per locus per generation. The new estimator has a variance only slightly larger than the minimum variance of all possible unbiased estimators of the parameter and is substantially smaller than that of any existing estimator. The high efficiency of the new estimator is achieved by making full use of phylogenetic information in a sample of DNA sequences from a population. An example of estimating theta by the new method is presented using the mitochondrial sequences from an American Indian population.

scholarly journals Initial Upper Palaeolithic humans in Europe had recent Neanderthal ancestry

Nature ◽  
2021 ◽  
Vol 592 (7853) ◽  
pp. 253-257 ◽  
Author(s):  
Mateja Hajdinjak ◽  
Fabrizio Mafessoni ◽  
Laurits Skov ◽  
Benjamin Vernot ◽  
Alexander Hübner ◽  
...  
Keyword(s):  
Family History ◽  
East Asia ◽  
Late Pleistocene ◽  
Modern Human ◽  
Human Migration ◽  
Upper Palaeolithic ◽  
Modern Humans ◽  
Genome Wide ◽  
Genome Wide Data

AbstractModern humans appeared in Europe by at least 45,000 years ago1–5, but the extent of their interactions with Neanderthals, who disappeared by about 40,000 years ago6, and their relationship to the broader expansion of modern humans outside Africa are poorly understood. Here we present genome-wide data from three individuals dated to between 45,930 and 42,580 years ago from Bacho Kiro Cave, Bulgaria1,2. They are the earliest Late Pleistocene modern humans known to have been recovered in Europe so far, and were found in association with an Initial Upper Palaeolithic artefact assemblage. Unlike two previously studied individuals of similar ages from Romania7 and Siberia8 who did not contribute detectably to later populations, these individuals are more closely related to present-day and ancient populations in East Asia and the Americas than to later west Eurasian populations. This indicates that they belonged to a modern human migration into Europe that was not previously known from the genetic record, and provides evidence that there was at least some continuity between the earliest modern humans in Europe and later people in Eurasia. Moreover, we find that all three individuals had Neanderthal ancestors a few generations back in their family history, confirming that the first European modern humans mixed with Neanderthals and suggesting that such mixing could have been common.

Review Feature: A review of The Mind in the Cave: Consciousness and the Origins of Art by David Lewis-Williams. London: Thames & Hudson, 2002. ISBN 0-500-05117-8 hardback £18.95 & US$29.95; 320 pp., 66 figs., 29 colour plates

2003 ◽  
Vol 13 (2) ◽  
pp. 263-279 ◽  
Author(s):  
David Lewis-Williams ◽  
E. Thomas Lawson ◽  
Knut Helskog ◽  
David S. Whitley ◽  
Paul Mellars
Keyword(s):  
Rock Art ◽  
David Lewis ◽  
Modern Human ◽  
Hominid Evolution ◽  
Modern Humans ◽  
Radiocarbon Dates ◽  
Anatomically Modern Humans ◽  
The Mind ◽  
Cave Art ◽  
West European

David Lewis-Williams is well-known in rock-art circles as the author of a series of articles drawing on ethnographic material and shamanism (notably connected with the San rock art of southern Africa) to gain new insights into the Palaeolithic cave art of western Europe. Some 15 years ago, with Thomas Dowson, he proposed that Palaeolithic art owed its inspiration at least in part to trance experiences (altered states of consciousness) associated with shamanistic practices. Since that article appeared, the shamanistic hypothesis has both been widely adopted and developed in the study of different rock-art traditions, and has become the subject of lively and sometimes heated controversy. In the present volume, Lewis-Williams takes the argument further, and combines the shamanistic hypothesis with an interpretation of the development of human consciousness. He thus enters another contentious area of archaeological debate, seeking to understand west European cave art in the context of (and as a marker of) the new intellectual capacities of anatomically modern humans. Radiocarbon dates for the earliest west European cave art now place it contemporary with the demise of the Neanderthals around 30,000 years ago, and cave art, along with carved or decorated portable items, appears to announce the arrival and denote the success of modern humans in this region. Lewis-Williams argues that such cave art would have been beyond the capabilities of Neanderthals, and that this kind of artistic ability is unique to anatomically modern humans. Furthermore, he concludes that the development of the new ability cannot have been the product of hundreds of thousands of years of gradual hominid evolution, but must have arisen much more abruptly, within the novel neurological structure of anatomically modern humans. The Mind in the Cave is thus the product of two hypotheses, both of them contentious — the shamanistic interpretation of west European Upper Palaeolithic cave art, and the cognitive separation of modern humans and Neanderthals. But is it as simple as that? Was cave art the hallmark of a new cognitive ability and social consciousness that were beyond the reach of previous hominids? And is shamanism an outgrowth of the hard-wired structure of the modern human brain? We begin this Review Feature with a brief summary by David Lewis-Williams of the book's principal arguments. There follows a series of comments addressing both the meaning of the west European cave art, and its wider relevance for the understanding of the Neanderthal/modern human transition.

scholarly journals Recent origin of low trabecular bone density in modern humans

2014 ◽  
Vol 112 (2) ◽  
pp. 366-371 ◽  
Author(s):  
Habiba Chirchir ◽  
Tracy L. Kivell ◽  
Christopher B. Ruff ◽  
Jean-Jacques Hublin ◽  
Kristian J. Carlson ◽  
...  
Keyword(s):  
Body Size ◽  
Trabecular Bone ◽  
Homo Sapiens ◽  
Modern Human ◽  
Homo Erectus ◽  
Lower Limbs ◽  
Modern Humans ◽  
Human Skeleton ◽  
Trabecular Density ◽  
Fossil Hominins

Humans are unique, compared with our closest living relatives (chimpanzees) and early fossil hominins, in having an enlarged body size and lower limb joint surfaces in combination with a relatively gracile skeleton (i.e., lower bone mass for our body size). Some analyses have observed that in at least a few anatomical regions modern humans today appear to have relatively low trabecular density, but little is known about how that density varies throughout the human skeleton and across species or how and when the present trabecular patterns emerged over the course of human evolution. Here, we test the hypotheses that (i) recent modern humans have low trabecular density throughout the upper and lower limbs compared with other primate taxa and (ii) the reduction in trabecular density first occurred in early Homo erectus, consistent with the shift toward a modern human locomotor anatomy, or more recently in concert with diaphyseal gracilization in Holocene humans. We used peripheral quantitative CT and microtomography to measure trabecular bone of limb epiphyses (long bone articular ends) in modern humans and chimpanzees and in fossil hominins attributed to Australopithecus africanus, Paranthropus robustus/early Homo from Swartkrans, Homo neanderthalensis, and early Homo sapiens. Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations.

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