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113-481: Estimates of the time when Y-MRCA lived have also shifted as modern knowledge of human ancestry changes. For example, in 2013, the discovery of a previously unknown Y-chromosomal haplogroup was announced, which resulted in a slight adjustment of the estimated age of the human Y-MRCA. By definition, it is not necessary that the Y-MRCA and the mt-MRCA should have lived at the same time. While estimates as of 2014 suggested

226-461: A terminus ante quem ("limit before which"), until the genome of the entire population has been examined (in this case, the genome of all living humans). Estimates on the age of the Y-MRCA crucially depend on the most archaic known haplogroup extant in contemporary populations. As of 2018, this is haplogroup A00 (discovered in 2013). Age estimates based on this published during 2014–2015 range between 160,000 and 300,000 years, compatible with

339-478: A Neanderthal from El Sidrón , Spain , produced a Y-T-MRCA (time to Y-MRCA) of 588,000 years ago for Neanderthal and Homo sapiens patrilineages, dubbed ante Adam, and 275,000 years ago for Y-MRCA. The Y-chromosomal most recent common ancestor is the most recent common ancestor of the Y-chromosomes found in currently living human males. Due to the definition via the "currently living" population,

452-610: A monophyletic clade. Haplogroup A therefore refers to a collection of lineages that do not possess the markers that define Haplogroup BT, though Haplogroup A includes the most distantly related Y chromosomes. The M91 and P97 mutations distinguish Haplogroup A from Haplogroup BT. Within Haplogroup A chromosomes, the M91 marker consists of a stretch of 8 T nucleobase units. In Haplogroup BT and chimpanzee chromosomes, this marker consists of 9 T nucleobase units. This pattern suggested that

565-1045: A 2017 study to be between 350 and 260,000 years ago, compatible with the estimated age of early H. sapiens . The study states that the deep split-time estimation of 350 to 260 thousand years ago is consistent with the archaeological estimate for the onset of the Middle Stone Age across sub-Saharan Africa and coincides with archaic H. sapiens in southern Africa represented by, for example, the Florisbad skull dating to 259 (± 35) thousand years ago. H. s. idaltu , found at Middle Awash in Ethiopia, lived about 160,000 years ago, and H. sapiens lived at Omo Kibish in Ethiopia about 233,000-195,000 years ago. Two fossils from Guomde, Kenya, dated to at least (and likely more than) 180,000 years ago and (more precisely) to 300–270,000 years ago, have been tentatively assigned to H. sapiens and similarities have been noted between them and

678-541: A DNA sequence is determined by comparing human DNA sequences with those of a closely related species, usually non-human primates such as chimpanzees and gorillas. By reversing known mutations in a Y-chromosome lineage, a hypothetical ancestral sequence for the MRCA, Y-chromosomal Adam, can be inferred. Determining the Y-MRCA's DNA sequence, and the time when he lived, involves identifying the human Y-chromosome lineages that are most divergent from each other—the lineages that share

791-483: A Neanderthal patrilineal line would immediately push back T-MRCA ("time to MRCA") to at least twice its current estimate. However, the discovery of a Neanderthal Y-chromosome by Mendez et al . suggests the extinction of Neanderthal patrilineages, as the lineage inferred from the Neanderthal sequence is outside of the range of contemporary human genetic variation. Questions of geographical origin would become part of

904-542: A cluster of Y-MRCAs in a window close to 50 kya ( out-of-Africa migration ), and an additional bottleneck for non-African populations at about 10 kya, interpreted as reflecting cultural changes increasing the variance in male reproductive success (i.e. increased social stratification ) in the Neolithic . Initial sequencing (Karafet et al., 2008) of the human Y chromosome suggested that two most basal Y-chromosome lineages were Haplogroup A and Haplogroup BT . Haplogroup A

1017-607: A common patrilineal ancestor who was the first to carry the defining mutation. (This assumption could be mistaken, as it is possible for the same mutation to occur more than once.) A family tree of Y chromosomes can be constructed, with the mutations serving as branching points along lineages. The Y-MRCA is positioned at the root of the family tree, as the Y chromosomes of all living males are descended from his Y chromosome. Researchers can reconstruct ancestral Y chromosome DNA sequences by reversing mutated DNA segments to their original condition. The most likely original or ancestral state of

1130-463: A comparatively homogeneous single species of H. sapiens from more diverse varieties of archaic humans (all of which were descended from the early dispersal of H. erectus some 1.8 million years ago) was debated in terms of two competing models during the 1980s: " recent African origin " postulated the emergence of H. sapiens from a single source population in Africa, which expanded and led to

1243-468: A convention popular in the 1990s, Neanderthals were classified as a subspecies of H. sapiens , as H. s. neanderthalensis , while AMH (or European early modern humans , EEMH) was taken to refer to " Cro-Magnon " or H. s. sapiens . Under this nomenclature (Neanderthals considered H. sapiens ), the term "anatomically modern Homo sapiens " (AMHS) has also been used to refer to EEMH ("Cro-Magnons"). It has since become more common to designate Neanderthals as

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1356-504: A favored allele will tend to increase exponentially in frequency when rare. Genome size is influenced by the amount of repetitive DNA as well as number of genes in an organism. Some organisms, such as most bacteria, Drosophila , and Arabidopsis have particularly compact genomes with little repetitive content or non-coding DNA. Other organisms, like mammals or maize, have large amounts of repetitive DNA, long introns , and substantial spacing between genes. The C-value paradox refers to

1469-406: A higher forehead, and reduced brow ridge . Early modern people and some living people do however have quite pronounced brow ridges, but they differ from those of archaic forms by having both a supraorbital foramen or notch, forming a groove through the ridge above each eye. This splits the ridge into a central part and two distal parts. In current humans, often only the central section of the ridge

1582-466: A new SNP . Cruciani et al. 2011, determined that the deepest split in the Y-chromosome tree was found between two previously reported subclades of Haplogroup A, rather than between Haplogroup A and Haplogroup BT. Later, group A00 was found, outside of the previously known tree. The rearrangement of the Y-chromosome family tree implies that lineages classified as Haplogroup A do not necessarily form

1695-661: A novel gene sequence. Chimeras often cause regulatory changes and can shuffle protein domains to produce novel adaptive functions. De novo gene birth can give rise to protein-coding genes and non-coding genes from previously non-functional DNA. For instance, Levine and colleagues reported the origin of five new genes in the D. melanogaster genome. Similar de novo origin of genes has been also shown in other organisms such as yeast, rice and humans. De novo genes may evolve from spurious transcripts that are already expressed at low levels. Constructive neutral evolution (CNE) explains that complex systems can emerge and spread into

1808-503: A number of physiological details which can be taken as reliably differentiating the physiology of Neanderthals vs. anatomically modern humans. The term "anatomically modern humans" (AMH) is used with varying scope depending on context, to distinguish "anatomically modern" Homo sapiens from archaic humans such as Neanderthals and Middle and Lower Paleolithic hominins with transitional features intermediate between H. erectus , Neanderthals and early AMH called archaic Homo sapiens . In

1921-607: A population through neutral transitions with the principles of excess capacity, presuppression, and ratcheting, and it has been applied in areas ranging from the origins of the spliceosome to the complex interdependence of microbial communities . The Society for Molecular Biology and Evolution publishes the journals "Molecular Biology and Evolution" and "Genome Biology and Evolution" and holds an annual international meeting. Other journals dedicated to molecular evolution include Journal of Molecular Evolution and Molecular Phylogenetics and Evolution . Research in molecular evolution

2034-405: A result of small effective population sizes. With a smaller effective population size, a larger variety of mutations will behave as if they are neutral due to inefficiency of selection. Gene conversion occurs during recombination, when nucleotide damage is repaired using an homologous genomic region as a template. It can be a biased process, i.e. one allele may have a higher probability of being

2147-486: A separate species, H. neanderthalensis , so that AMH in the European context refers to H. sapiens , but the question is by no means resolved. In this more narrow definition of H. sapiens , the subspecies Homo sapiens idaltu , discovered in 2003, also falls under the umbrella of "anatomically modern". The recognition of H. sapiens idaltu as a valid subspecies of the anatomically modern human lineage would justify

2260-471: A single pair of chromosomes whereas the Adders-tongue fern Ophioglossum reticulatum has up to 1260 chromosomes. The number of chromosomes in an organism's genome does not necessarily correlate with the amount of DNA in its genome. The genome-wide amount of recombination is directly controlled by the number of chromosomes, with one crossover per chromosome or per chromosome arm, depending on

2373-508: A smaller, more receded dentary, making the rest of the jaw-line stand out, giving an often quite prominent chin. The central part of the mandible forming the chin carries a triangularly shaped area forming the apex of the chin called the mental trigon , not found in archaic humans. Particularly in living populations, the use of fire and tools requires fewer jaw muscles, giving slender, more gracile jaws. Compared to archaic people, modern humans have smaller, lower faces. The body skeletons of even

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2486-576: A study published in 2020, there are indications that 2% to 19% (or about ≃6.6 and ≃7.0%) of the DNA of four West African populations may have come from an unknown archaic hominin which split from the ancestor of humans and Neanderthals between 360 kya to 1.02 mya. Generally, modern humans are more lightly built (or more "gracile") than the more "robust" archaic humans . Nevertheless, contemporary humans exhibit high variability in many physiological traits , and may exhibit remarkable "robustness". There are still

2599-498: A virtual skull shape of the last common human ancestor to modern humans/ H. sapiens , representative of the earliest modern humans, and suggested that modern humans arose between 350,000 and 260,000 years ago through a merging of populations in East and South Africa while North-African fossils may represent a population which introgressed into Neandertals during the LMP. According to

2712-694: Is associated with the African megadroughts during MIS 5 , beginning 130,000 years ago. A 2011 study located the origin of basal population of contemporary human populations at 130,000 years ago, with the Khoi-San representing an "ancestral population cluster" located in southwestern Africa (near the coastal border of Namibia and Angola ). While early modern human expansion in Sub-Saharan Africa before 130 kya persisted, early expansion to North Africa and Asia appears to have mostly disappeared by

2825-415: Is determined by applying a molecular clock to human Y-chromosomes. In contrast to mitochondrial DNA (mtDNA), which has a short sequence of 16,000 base pairs , and mutates frequently, the Y chromosome is significantly longer at 60 million base pairs, and has a lower mutation rate. These features of the Y chromosome have slowed down the identification of its polymorphisms; as a consequence, they have reduced

2938-401: Is equal to the mutation rate per replication. A relatively constant mutation rate thus produces a constant rate of change per generation (molecular clock). Slightly deleterious mutations with a selection coefficient less than a threshold value of 1 / the effective population size can also fix. Many genomic features have been ascribed to accumulation of nearly neutral detrimental mutations as

3051-484: Is estimated as having taken place over 500,000 years ago (marking the split of the H. sapiens lineage from ancestors shared with other known archaic hominins). But the oldest split among modern human populations (such as the Khoisan split from other groups) has been recently dated to between 350,000 and 260,000 years ago, and the earliest known examples of H. sapiens fossils also date to about that period, including

3164-553: Is evidence that the characteristic human brain development, especially the prefrontal cortex, was due to "an exceptional acceleration of metabolome evolution ... paralleled by a drastic reduction in muscle strength. The observed rapid metabolic changes in brain and muscle, together with the unique human cognitive skills and low muscle performance, might reflect parallel mechanisms in human evolution." The Schöningen spears and their correlation of finds are evidence that complex technological skills already existed 300,000 years ago, and are

3277-547: Is far higher than that of mammals, due largely to flight, and oxygen needs are high. Hence, most birds have small, compact genomes with few repetitive elements. Indirect evidence suggests that non-avian theropod dinosaur ancestors of modern birds also had reduced genome sizes, consistent with endothermy and high energetic needs for running speed. Many bacteria have also experienced selection for small genome size, as time of replication and energy consumption are so tightly correlated with fitness. The ant Myrmecia pilosula has only

3390-406: Is found at low frequencies in parts of Africa, but is common among certain hunter-gatherer groups. Haplogroup BT lineages represent the majority of African Y-chromosome lineages and virtually all non-African lineages. Y-chromosomal Adam was represented as the root of these two lineages. Haplogroup A and Haplogroup BT represented the lineages of Y-chromosomal Adam himself and of one of his sons, who had

3503-475: Is of the order of about 1% to 4% in Europeans and East Asians, and highest among Melanesians (the last also having Denisova hominin admixture at 4% to 6% in addition to neanderthal admixture). Cumulatively, about 20% of the Neanderthal genome is estimated to remain present spread in contemporary populations. In September 2019, scientists reported the computerized determination, based on 260 CT scans , of

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3616-416: Is often found for genes involved in intragenomic conflict , sexual antagonistic coevolution , and the immune system . Genetic drift is the change of allele frequencies from one generation to the next due to stochastic effects of random sampling in finite populations. These effects can accumulate until a mutation becomes fixed in a population . For neutral mutations, the rate of fixation per generation

3729-477: Is preserved (if it is preserved at all). This contrasts with archaic humans, where the brow ridge is pronounced and unbroken. Modern humans commonly have a steep, even vertical forehead whereas their predecessors had foreheads that sloped strongly backwards. According to Desmond Morris , the vertical forehead in humans plays an important role in human communication through eyebrow movements and forehead skin wrinkling. Brain size in both Neanderthals and AMH

3842-521: Is significantly larger on average (but overlapping in range) than brain size in H. erectus . Neanderthal and AMH brain sizes are in the same range, but there are differences in the relative sizes of individual brain areas, with significantly larger visual systems in Neanderthals than in AMH. Compared to archaic people, anatomically modern humans have smaller, differently shaped teeth. This results in

3955-445: Is taken to reflect a process towards a smaller and more fine-boned skeleton beginning around 50,000–30,000 years ago. The cranium lacks a pronounced occipital bun in the neck, a bulge that anchored considerable neck muscles in Neanderthals. Modern humans, even the earlier ones, generally have a larger fore-brain than the archaic people, so that the brain sits above rather than behind the eyes. This will usually (though not always) give

4068-846: Is useful especially for times and regions where anatomically modern and archaic humans co-existed, for example, in Paleolithic Europe . Among the oldest known remains of Homo sapiens are those found at the Omo-Kibish I archaeological site in south-western Ethiopia , dating to about 233,000 to 196,000 years ago, the Florisbad site in South Africa, dating to about 259,000 years ago, and the Jebel Irhoud site in Morocco, dated about 315,000 years ago. Extinct species of

4181-688: The Arctic . Both Neanderthal and EEMH had somewhat larger cranial volumes on average than modern Europeans, suggesting the relaxation of selection pressures for larger brain volume after the end of the LGM. Examples for still later adaptations related to agriculture and animal domestication including East Asian types of ADH1B associated with rice domestication , or lactase persistence , are due to recent selection pressures. Molecular evolution Molecular evolution describes how inherited DNA and/or RNA change over evolutionary time, and

4294-609: The Jebel Irhoud remains from Morocco (ca. 300,000 or 350–280,000 years ago), the Florisbad Skull from South Africa (ca. 259,000 years ago), and the Omo remains from Ethiopia (ca. 195,000, or, as more recently dated, ca. 233,000 years ago). An mtDNA study in 2019 proposed an origin of modern humans in Botswana (and a Khoisan split) of around 200,000 years. However, this proposal has been widely criticized by scholars, with

4407-519: The Mesolithic and the Neolithic , due to increased selection pressures and due to founder effects associated with migration . Alleles predictive of light skin have been found in Neanderthals , but the alleles for light skin in Europeans and East Asians, associated with KITLG and ASIP , are (as of 2012 ) thought to have not been acquired by archaic admixture but recent mutations since

4520-459: The brain case is quite rounded and distinct from that of the Neanderthals and is similar to the brain case of modern humans. It is uncertain whether the robust traits of some of the early modern humans like Skhul V reflects mixed ancestry or retention of older traits. The "gracile" or lightly built skeleton of anatomically modern humans has been connected to a change in behavior, including increased cooperation and "resource transport". There

4633-499: The evolution of development , and patterns and processes underlying genomic changes during evolution. The history of molecular evolution starts in the early 20th century with comparative biochemistry , and the use of "fingerprinting" methods such as immune assays, gel electrophoresis , and paper chromatography in the 1950s to explore homologous proteins . The advent of protein sequencing allowed molecular biologists to create phylogenies based on sequence comparison, and to use

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4746-603: The lipid catabolic process . A 2017 study found correlation of Neanderthal admixture in phenotypic traits in modern European populations. Physiological or phenotypical changes have been traced to Upper Paleolithic mutations, such as the East Asian variant of the EDAR gene, dated to c. 35,000 years ago. Recent divergence of Eurasian lineages was sped up significantly during the Last Glacial Maximum (LGM),

4859-850: The recent "out of Africa" migration , likely between 60,000 and 40,000 years ago. Recent admixture analyses have added to the complexity, finding that Eastern Neanderthals derive up to 2% of their ancestry from anatomically modern humans who left Africa some 100 kya . The extent of Neanderthal admixture (and introgression of genes acquired by admixture) varies significantly between contemporary racial groups, being absent in Africans, intermediate in Europeans and highest in East Asians. Certain genes related to UV-light adaptation introgressed from Neanderthals have been found to have been selected for in East Asians specifically from 45,000 years ago until around 5,000 years ago. The extent of archaic admixture

4972-443: The 1970s, nucleic acid sequencing allowed molecular evolution to reach beyond proteins to highly conserved ribosomal RNA sequences, the foundation of a reconceptualization of the early history of life . The Society for Molecular Biology and Evolution was founded in 1982. Molecular phylogenetics uses DNA , RNA , or protein sequences to resolve questions in systematics , i.e. about their correct scientific classification from

5085-474: The 1980s all extant groups have tended to be subsumed into a single species, H. sapiens , avoiding division into subspecies altogether. Some sources show Neanderthals ( H. neanderthalensis ) as a subspecies ( H. sapiens neanderthalensis ). Similarly, the discovered specimens of the H. rhodesiensis species have been classified by some as a subspecies ( H. sapiens rhodesiensis ), although it remains more common to treat these last two as separate species within

5198-689: The 2010s with the discovery of admixture events ( introgression ) of populations of H. sapiens with populations of archaic humans over the period of between roughly 100,000 and 30,000 years ago, both in Eurasia and in Sub-Saharan Africa. Neanderthal admixture , in the range of 1–4%, is found in all modern populations outside of Africa, including in Europeans, Asians, Papua New Guineans, Australian Aboriginals, Native Americans, and other non-Africans. This suggests that interbreeding between Neanderthals and anatomically modern humans took place after

5311-456: The 8T stretch of Haplogroup A may be the ancestral state of M91 and the 9T of Haplogroup BT may be the derived state that arose by an insertion of 1T. This would explain why subclades A1b and A1a-T, the deepest branches of Haplogroup A, both possess the same version of M91 with 8Ts. Furthermore, Cruciani et al. 2011 determined that the P97 marker, which is also used to identify Haplogroup A, possessed

5424-399: The 9T stretch of Haplogroup BT was the ancestral version and that Haplogroup A was formed by the deletion of one nucleobase . Haplogroups A1b and A1a were considered subclades of Haplogroup A as they both possessed the M91 with 8Ts. But according to Cruciani et al. 2011, the region surrounding the M91 marker is a mutational hotspot prone to recurrent mutations. It is therefore possible that

5537-498: The Americas by about 40,000–25,000 years ago. Evidence for the overwhelming contribution of this "recent" ( L3 -derived) expansion to all non-African populations was established based on mitochondrial DNA , combined with evidence based on physical anthropology of archaic specimens , during the 1990s and 2000s, and has also been supported by Y DNA and autosomal DNA . The assumption of complete replacement has been revised in

5650-627: The DNA fall within a region coding for a protein , they are characterized by whether they are synonymous (do not change the amino acid sequence) or non-synonymous. Other types of mutations modify larger segments of DNA and can cause duplications, insertions, deletions, inversions, and translocations. The distribution of rates for diverse kinds of mutations is called the "mutation spectrum" (see App. B of ). Mutations of different types occur at widely varying rates. Point mutation rates for most organisms are very low, roughly 10 to 10 per site per generation, though some viruses have higher mutation rates on

5763-399: The LGM. Phenotypes associated with the " white " or " Caucasian " populations of Western Eurasian stock emerge during the LGM, from about 19,000 years ago. Average cranial capacity in modern human populations varies in the range of 1,200 to 1,450 cm for adult males. Larger cranial volume is associated with climatic region, the largest averages being found in populations of Siberia and

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5876-438: The Neanderthal lineage, as "pre-Neanderthal" or "early Neanderthal", while the divergence time between the Neanderthal and modern lineages has been pushed back to before the emergence of H. heidelbergensis , to close to 800,000 years ago, the approximate time of disappearance of H. antecessor . The term Middle Paleolithic is intended to cover the time between the first emergence of H. sapiens (roughly 300,000 years ago) and

5989-784: The Omo Kibbish remains. Fossil evidence for modern human presence in West Asia is ascertained for 177,000 years ago, and disputed fossil evidence suggests expansion as far as East Asia by 120,000 years ago. In July 2019, anthropologists reported the discovery of 210,000 year old remains of a H. sapiens and 170,000 year old remains of a H. neanderthalensis in Apidima Cave , Peloponnese , Greece , more than 150,000 years older than previous H. sapiens finds in Europe. A significant dispersal event, within Africa and to West Asia,

6102-436: The X chromosome in the pseudoautosomal regions at the ends of the Y chromosome. Mutations occur periodically within the Y chromosome, and these mutations are passed on to males in subsequent generations. These mutations can be used as markers to identify shared patrilineal relationships. Y chromosomes that share a specific mutation are referred to as haplogroups . Y chromosomes within a specific haplogroup are assumed to share

6215-447: The Y-MRCA lived about 84,000 years after his female counterpart mt-MRCA (the matrilineal most recent common ancestor), who lived 150,000–200,000 years ago. This date also meant that Y-chromosomal Adam lived at a time very close to, and possibly after, the migration from Africa which is believed to have taken place 50,000–80,000 years ago. One explanation given for this discrepancy in the time depths of patrilineal vs. matrilineal lineages

6328-543: The Y-MRCA living in the general region of "Central-Northwest Africa". Scozzari et al. (2012) agreed with a plausible placement in "the north-western quadrant of the African continent" for the emergence of the A1b haplogroup. The 2013 report of haplogroup A00 found among the Mbo people of western present-day Cameroon is also compatible with this picture. The revision of Y-chromosomal phylogeny since 2011 has affected estimates for

6441-433: The Y-MRCA to have lived between 120,000 and 156,000 years ago, based on genome sequencing of 69 men from 9 different populations. In addition, the same study estimated the age of Mitochondrial Eve to about 99,000 and 148,000 years. As these ranges overlap for a time-range of 28,000 years (148 to 120 kya), the results of this study have been cast in terms of the possibility that "Genetic Adam and Eve may have walked on Earth at

6554-455: The accuracy of Y-chromosome mutation rate estimates. Methods of estimating the age of the Y-MRCA for a population of human males whose Y-chromosomes have been sequenced are based on applying the theories of molecular evolution to the Y chromosome . Unlike the autosomes , the human Y-chromosome does not recombine often with the X chromosome during meiosis , but is usually transferred intact from father to son; however, it can recombine with

6667-525: The age of Y-chromosomal Adam have been pushed back significantly with the discovery of an ancient Y-chromosomal lineage in 2013, to likely beyond 300,000 years ago. There have, however, been no reports of the survival of Y-chromosomal or mitochondrial DNA clearly deriving from archaic humans (which would push back the age of the most recent patrilinear or matrilinear ancestor beyond 500,000 years). Fossil teeth found at Qesem Cave (Israel) and dated to between 400,000 and 200,000 years ago have been compared to

6780-675: The ancestral state in Haplogroup A but the derived state in Haplogroup BT. As current estimates on TMRCA converge with estimates for the age of anatomically modern humans and well predate the Out of Africa migration, geographical origin hypotheses continue to be limited to the African continent . According to Cruciani et al. 2011, the most basal lineages have been detected in West , Northwest and Central Africa , suggesting plausibility for

6893-447: The bearer of the chromosome was the only human male alive during his time. His other male contemporaries may also have descendants alive today, but not, by definition, through solely patrilineal descent; in other words, none of them have an unbroken male line of descendants ( son's son's son's … son ) connecting them to currently living people. By the nature of the concept of most recent common ancestors, these estimates can only represent

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7006-431: The consequences of this for proteins and other components of cells and organisms . Molecular evolution is the basis of phylogenetic approaches to describing the tree of life . Molecular evolution overlaps with population genetics , especially on shorter timescales. Topics in molecular evolution include the origins of new genes, the genetic nature of complex traits , the genetic basis of adaptation and speciation ,

7119-491: The contemporary height distribution measured among Malay people , for one. Following the peopling of Africa some 130,000 years ago, and the recent Out-of-Africa expansion some 70,000 to 50,000 years ago, some sub-populations of H. sapiens had been essentially isolated for tens of thousands of years prior to the early modern Age of Discovery . Combined with archaic admixture this has resulted in significant genetic variation , which in some instances has been shown to be

7232-405: The debate on Neanderthal evolution from Homo erectus . Anatomically modern humans Early modern human ( EMH ), or anatomically modern human ( AMH ), are terms used to distinguish Homo sapiens (the only extant Hominina species) that are anatomically consistent with the range of phenotypes seen in contemporary humans, from extinct archaic human species. This distinction

7345-658: The dental material from the younger (120,000–80,000 years ago) Skhul and Qafzeh hominins . Dispersal of early H. sapiens begins soon after its emergence, as evidenced by the North African Jebel Irhoud finds (dated to around 315,000 years ago). There is indirect evidence for H. sapiens presence in West Asia around 270,000 years ago. The Florisbad Skull from Florisbad, South Africa, dated to about 259,000 years ago, has also been classified as representing early H. sapiens . Scerri (2018) , pp. 582–594 In September 2019, scientists proposed that

7458-412: The description of contemporary humans with the subspecies name Homo sapiens sapiens . However, biological anthropologist Chris Stringer does not consider idaltu distinct enough within H. sapiens to warrant its own subspecies designation. A further division of AMH into "early" or "robust" vs. "post-glacial" or " gracile " subtypes has since been used for convenience. The emergence of "gracile AMH"

7571-425: The differences between homologous sequences as a molecular clock to estimate the time since the most recent common ancestor . The surprisingly large amount of molecular divergence within and between species inspired the neutral theory of molecular evolution in the late 1960s. Neutral theory also provided a theoretical basis for the molecular clock , although this is not needed for the clock's validity. After

7684-623: The distal bones were shorter, usually thought to be an adaptation to cold climate. The same adaptation is found in some modern people living in the polar regions. Height ranges overlap between Neanderthals and AMH, with Neanderthal averages cited as 164 to 168 cm (65 to 66 in) and 152 to 156 cm (60 to 61 in) for males and females, respectively, which is largely identical to pre-industrial average heights for AMH. Contemporary national averages range between 158 to 184 cm (62 to 72 in) in males and 147 to 172 cm (58 to 68 in) in females. Neanderthal ranges approximate

7797-538: The donor than the other in a gene conversion event. In particular, GC-biased gene conversion tends to increase the GC-content of genomes, particularly in regions with higher recombination rates. There is also evidence for GC bias in the mismatch repair process. It is thought that this may be an adaptation to the high rate of methyl-cytosine deamination which can lead to C→T transitions. The dynamics of biased gene conversion resemble those of natural selection, in that

7910-493: The earliest H. sapiens (and last common human ancestor to modern humans) arose between 350,000 and 260,000 years ago through a merging of populations in East and South Africa . Among extant populations, the Khoi-San (or " Capoid ") hunters-gatherers of Southern Africa may represent the human population with the earliest possible divergence within the group Homo sapiens sapiens . Their separation time has been estimated in

8023-437: The earliest and most robustly built modern humans were less robust than those of Neanderthals (and from what little we know from Denisovans), having essentially modern proportions. Particularly regarding the long bones of the limbs, the distal bones (the radius / ulna and tibia / fibula ) are nearly the same size or slightly shorter than the proximal bones (the humerus and femur ). In ancient people, particularly Neanderthals,

8136-467: The earliest genetic splits among modern people, according to some evidence, dating to around the same time. Sustained archaic human admixture with modern humans is known to have taken place both in Africa and (following the recent Out-Of-Africa expansion ) in Eurasia, between about 100,000 and 30,000 years ago. The binomial name Homo sapiens was coined by Linnaeus , 1758 . The Latin noun homō (genitive hominis ) means "human being", while

8249-575: The emergence of "anatomically modern humans". Since the 2000s, the discovery of older remains with comparable characteristics, and the discovery of ongoing hybridization between "modern" and "archaic" populations after the time of the Omo remains, have opened up a renewed debate on the age of H. sapiens in journalistic publications. H. s. idaltu , dated to 160,000 years ago, has been postulated as an extinct subspecies of H. sapiens in 2003. H. neanderthalensis , which became extinct about 40,000 years ago,

8362-433: The emergence of a much more detailed picture, intermediate between the two competing scenarios outlined above: The recent Out-of-Africa expansion accounts for the predominant part of modern human ancestry, while there were also significant admixture events with regional archaic humans. Since the 1970s, the Omo remains, originally dated to some 195,000 years ago, have often been taken as the conventional cut-off point for

8475-802: The end of MIS5 (75,000 years ago), and is known only from fossil evidence and from archaic admixture . Eurasia was re-populated by early modern humans in the so-called "recent out-of-Africa migration" post-dating MIS5, beginning around 70,000–50,000 years ago. In this expansion, bearers of mt-DNA haplogroup L3 left East Africa, likely reaching Arabia via the Bab-el-Mandeb , and in the Great Coastal Migration spread to South Asia, Maritime South Asia and Oceania between 65,000 and 50,000 years ago, while Europe , East and North Asia were reached by about 45,000 years ago. Some evidence suggests that an early wave of humans may have reached

8588-514: The expense of organismal fitness, resulting in intragenomic conflict . This is because there can be a selective advantage for selfish genetic elements in spite of a host cost. Examples of such selfish elements include transposable elements , meiotic drivers , and selfish mitochondria . Selection can be detected using the Ka/Ks ratio , the McDonald–Kreitman test . Rapid adaptive evolution

8701-486: The extinction of all other human varieties, while the " multiregional evolution " model postulated the survival of regional forms of archaic humans, gradually converging into the modern human varieties by the mechanism of clinal variation , via genetic drift , gene flow and selection throughout the Pleistocene. Since the 2000s, the availability of data from archaeogenetics and population genetics has led to

8814-548: The fewest mutations with each other when compared to a non-human primate sequence in a phylogenetic tree . The common ancestor of the most divergent lineages is therefore the common ancestor of all lineages. Early estimates of the age for the Y-MRCA published during the 1990s ranged between roughly 200 and 300 thousand years ago (kya). Such estimates were later substantially revised downward, as in Thomson et al. 2000, which proposed an age of about 59,000. This date suggested that

8927-436: The first descendant is reached who had at least two sons who both have living, patrilineal descendants. The title of Y-MRCA is not permanently fixed to a single individual, and the Y-MRCA for any given population would himself have been part of a population which had its own, more remote, Y-MRCA. Although the informal name "Y-chromosomal Adam" is a reference to the biblical Adam , this should not be misconstrued as implying that

9040-486: The first obvious proof of an active (big game) hunt . H. heidelbergensis already had intellectual and cognitive skills like anticipatory planning, thinking and acting that so far have only been attributed to modern man. The ongoing admixture events within anatomically modern human populations make it difficult to estimate the age of the matrilinear and patrilinear most recent common ancestors of modern populations ( Mitochondrial Eve and Y-chromosomal Adam ). Estimates of

9153-695: The function of a protein. Directed evolution is the attempt to engineer proteins using methods inspired by molecular evolution. Change at one locus begins with a new mutation , which might become fixed due to some combination of natural selection , genetic drift , and gene conversion . Mutations are permanent, transmissible changes to the genetic material ( DNA or RNA ) of a cell or virus . Mutations result from errors in DNA replication during cell division and by exposure to radiation , chemicals, other environmental stressors, viruses , or transposable elements . When point mutations to just one base-pair of

9266-399: The future. These fewer male lineages are more sensitive to drift and would most likely coalesce on a more recent common ancestor. This would potentially explain the more recent dates associated with the Y-MRCA. The "hyper-recent" estimate of significantly below 100 kya was again corrected upward in studies of the early 2010s, which ranged at about 120 kya to 160 kya. This revision was due to

9379-572: The genus Homo include Homo erectus (extant from roughly 2 to 0.1 million years ago) and a number of other species (by some authors considered subspecies of either H. sapiens or H. erectus ). The divergence of the lineage leading to H. sapiens out of ancestral H. erectus (or an intermediate species such as Homo antecessor ) is estimated to have occurred in Africa roughly 500,000 years ago. The earliest fossil evidence of early modern humans appears in Africa around 300,000 years ago, with

9492-438: The genus Homo rather than as subspecies within H. sapiens . All humans are considered to be a part of the subspecies H. sapiens sapiens , a designation which has been a matter of debate since a species is usually not given a subspecies category unless there is evidence of multiple distinct subspecies. The divergence of the lineage that would lead to H. sapiens out of archaic human varieties derived from H. erectus ,

9605-474: The highest rates of speciation identified to date. Cilliate genomes house each gene in individual chromosomes. In addition to the nuclear genome , endosymbiont organelles contain their own genetic material. Mitochondrial and chloroplast DNA varies across taxa, but membrane-bound proteins , especially electron transport chain constituents are most often encoded in the organelle. Chloroplasts and mitochondria are maternally inherited in most species, as

9718-409: The identity of a MRCA, and by extension of the human Y-MRCA, is time-dependent (it depends on the moment in time intended by the term "currently"). The MRCA of a population may move forward in time as archaic lineages within the population go extinct: once a lineage has died out, it is irretrievably lost. This mechanism can thus only shift the title of Y-MRCA forward in time. Such an event could be due to

9831-416: The introduction of variation (arrival bias). Selection can occur when an allele confers greater fitness , i.e. greater ability to survive or reproduce, on the average individual than carries it. A selectionist approach emphasizes e.g. that biases in codon usage are due at least in part to the ability of even weak selection to shape molecular evolution. Selection can also operate at the gene level at

9944-418: The lack of correlation between organism 'complexity' and genome size. Explanations for the so-called paradox are two-fold. First, repetitive genetic elements can comprise large portions of the genome for many organisms, thereby inflating DNA content of the haploid genome. Repetitive genetic elements are often descended from transposable elements . Secondly, the number of genes is not necessarily indicative of

10057-463: The likely geographical origin of Y-MRCA as well as estimates on time depth. By the same reasoning, future discovery of presently-unknown archaic haplogroups in living people would again lead to such revisions. In particular, the possible presence of between 1% and 4% Neanderthal-derived DNA in Eurasian genomes implies that the (unlikely) event of a discovery of a single living Eurasian male exhibiting

10170-500: The lineage of modern humans since the split from the lineage of Neanderthals , roughly 500,000 to 800,000 years ago. The time of divergence between archaic H. sapiens and ancestors of Neanderthals and Denisovans caused by a genetic bottleneck of the latter was dated at 744,000 years ago, combined with repeated early admixture events and Denisovans diverging from Neanderthals 300 generations after their split from H. sapiens , as calculated by Rogers et al. (2017). The derivation of

10283-579: The modern human lineage following the split from the Neanderthal lineage. Such a cladistic definition would extend the age of H. sapiens to over 500,000 years. Estimates for the split between the Homo sapiens line and combined Neanderthal / Denisovan line range from between 503,000 and 565,000 years ago; between 550,000 and 765,000 years ago; and (based on rates of dental evolution) possibly more than 800,000 years ago. Extant human populations have historically been divided into subspecies , but since around

10396-445: The new gene performs a subset of the original ancestral functions. Retrotransposition duplicates genes by copying mRNA to DNA and inserting it into the genome. Retrogenes generally insert into new genomic locations, lack introns . and sometimes develop new expression patterns and functions. Chimeric genes form when duplication, deletion, or incomplete retrotransposition combine portions of two different coding sequences to produce

10509-491: The number of developmental stages or tissue types in an organism. An organism with few developmental stages or tissue types may have large numbers of genes that influence non-developmental phenotypes, inflating gene content relative to developmental gene families. Neutral explanations for genome size suggest that when population sizes are small, many mutations become nearly neutral. Hence, in small populations repetitive content and other 'junk' DNA can accumulate without placing

10622-734: The order of 10 per generation. Different frequencies of different types of mutations can play an important role in evolution via bias in the introduction of variation (arrival bias), contributing to parallelism, trends, and differences in the navigability of adaptive landscapes. Mutation bias makes systematic or predictable contributions to parallel evolution . Since the 1960s, genomic GC content has been thought to reflect mutational tendencies. Mutational biases also contribute to codon usage bias . Although such hypotheses are often associated with neutrality, recent theoretical and empirical results have established that mutational tendencies can influence both neutral and adaptive evolution via bias in

10735-517: The order of 10 per site per generation. Transitions (A ↔ G or C ↔ T) are more common than transversions ( purine (adenine or guanine)) ↔ pyrimidine (cytosine or thymine, or in RNA, uracil)). Perhaps the most common type of mutation in humans is a change in the length of a short tandem repeat (e.g., the CAG repeats underlying various disease-associated mutations). Such STR mutations may occur at rates on

10848-536: The organelles must pass through the egg . In a rare departure, some species of mussels are known to inherit mitochondria from father to son. New genes arise from several different genetic mechanisms including gene duplication , de novo gene birth , retrotransposition , chimeric gene formation, recruitment of non-coding sequence into an existing gene, and gene truncation. Gene duplication initially leads to redundancy. However, duplicated gene sequences can mutate to develop new functions or specialize so that

10961-612: The organism at a competitive disadvantage. There is little evidence to suggest that genome size is under strong widespread selection in multicellular eukaryotes. Genome size, independent of gene content, correlates poorly with most physiological traits and many eukaryotes, including mammals, harbor very large amounts of repetitive DNA. However, birds likely have experienced strong selection for reduced genome size, in response to changing energetic needs for flight. Birds, unlike humans, produce nucleated red blood cells, and larger nuclei lead to lower levels of oxygen transport. Bird metabolism

11074-477: The participle sapiēns means "discerning, wise, sensible". The species was initially thought to have emerged from a predecessor within the genus Homo around 300,000 to 200,000 years ago. A problem with the morphological classification of "anatomically modern" was that it would not have included certain extant populations. For this reason, a lineage-based ( cladistic ) definition of H. sapiens has been suggested, in which H. sapiens would by definition refer to

11187-486: The period held by some to mark the emergence of full behavioral modernity (roughly by 50,000 years ago, corresponding to the start of the Upper Paleolithic ). Many of the early modern human finds, like those of Jebel Irhoud , Omo , Herto , Florisbad , Skhul , and Peștera cu Oase exhibit a mix of archaic and modern traits. Skhul V, for example, has prominent brow ridges and a projecting face. However,

11300-706: The point of view of evolutionary history . The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree . Phylogenetic inference is conducted using data from DNA sequencing . This is aligned to identify which sites are homologous . A substitution model describes what patterns are expected to be common or rare. Sophisticated computational inference is then used to generate one or more plausible trees. Some phylogenetic methods account for variation among sites and among tree branches . Different genes, e.g. hemoglobin vs. cytochrome c , generally evolve at different rates . These rates are relatively constant over time (e.g., hemoglobin does not evolve at

11413-410: The possibility that the two individuals may well have been roughly contemporaneous, the discovery of the archaic Y-haplogroup has pushed back the estimated age of the Y-MRCA beyond the most likely age of the mt-MRCA. As of 2015, estimates of the age of the Y-MRCA range around 200,000 to 300,000 years ago, roughly consistent with the emergence of anatomically modern humans . Y-chromosomal data taken from

11526-433: The rearrangement of the backbone of the Y-chromosome phylogeny following the resequencing of Haplogroup A lineages. In 2013, Francalacci et al. reported the sequencing of male-specific single-nucleotide Y-chromosome polymorphisms (MSY- SNPs ) from 1204 Sardinian males , which indicated an estimate of 180,000 to 200,000 years for the common origin of all humans through paternal lineage. Also in 2013, Poznik et al. reported

11639-508: The recent evidence overall (genetic, fossil, and archaeological) supporting an origin for H. sapiens approximately 100,000 years earlier and in a broader region of Africa than the study proposes. In September 2019, scientists proposed that the earliest H. sapiens (and last common human ancestor to modern humans) arose between 350,000 and 260,000 years ago through a merging of populations in East and South Africa . An alternative suggestion defines H. sapiens cladistically as including

11752-774: The result of directional selection taking place over the past 15,000 years, i.e., significantly later than possible archaic admixture events. Some climatic adaptations, such as high-altitude adaptation in humans , are thought to have been acquired by archaic admixture. Introgression of genetic variants acquired by Neanderthal admixture have different distributions in European and East Asians , reflecting differences in recent selective pressures. A 2014 study reported that Neanderthal-derived variants found in East Asian populations showed clustering in functional groups related to immune and haematopoietic pathways , while European populations showed clustering in functional groups related to

11865-492: The same rate as cytochrome c, but hemoglobins from humans, mice, etc. do have comparable rates of evolution), although rapid evolution along one branch can indicate increased directional selection on that branch. Purifying selection causes functionally important regions to evolve more slowly, and amino acid substitutions involving similar amino acids occurs more often than dissimilar substitutions. Gene duplication can produce multiple homologous proteins (paralogs) within

11978-536: The same species. Phylogenetic analysis of proteins has revealed how proteins evolve and change their structure and function over time. For example, ribonucleotide reductase (RNR) has evolved a multitude of structural and functional variants. Class I RNRs use a ferritin subunit and differ by the metal they use as cofactors. In class II RNRs, the thiyl radical is generated using an adenosylcobalamin cofactor and these enzymes do not require additional subunits (as opposed to class I which do). In class III RNRs,

12091-595: The same time" in the popular press. The announcement by Mendez et al. of the discovery of a previously unknown lineage, haplogroup A00 , in 2013, resulted in another shift in the estimate for the age of Y-chromosomal Adam. The authors estimated the split from the other haplogroups at 338,000 years ago (95% confidence interval 237–581 kya), but later Elhaik et al. (2014) dated it to between 163,900 and 260,200 years ago ( 95% CI ), and Karmin et al. (2015) dated it to between 192,000 and 307,000 years ago ( 95% CI ). The same study reports that non-African populations converge to

12204-591: The species. Changes in chromosome number can play a key role in speciation , as differing chromosome numbers can serve as a barrier to reproduction in hybrids. Human chromosome 2 was created from a fusion of two chimpanzee chromosomes and still contains central telomeres as well as a vestigial second centromere . Polyploidy , especially allopolyploidy, which occurs often in plants, can also result in reproductive incompatibilities with parental species. Agrodiatus blue butterflies have diverse chromosome numbers ranging from n=10 to n=134 and additionally have one of

12317-459: The thiyl radical is generated using S-adenosylmethionine bound to a [ 4Fe-4S ] cluster. That is, within a single family of proteins numerous structural and functional mechanisms can evolve. In a proof-of-concept study, Bhattacharya and colleagues converted myoglobin , a non-enzymatic oxygen storage protein, into a highly efficient Kemp eliminase using only three mutations . This demonstrates that only few mutations are needed to radically change

12430-429: The time of emergence and early dispersal of Homo sapiens . In addition to the tendency of the title of Y-MRCA to shift forward in time, the estimate of the Y-MRCA's DNA sequence, his position in the family tree, the time when he lived, and his place of origin, are all subject to future revisions. The following events would change the estimate of who the individual designated as Y-MRCA was: The time when Y-MRCA lived

12543-422: The total extinction of several basal haplogroups. The same holds for the concepts of matrilineal and patrilineal MRCAs: it follows from the definition of Y-MRCA that he had at least two sons who both have unbroken lineages that have survived to the present day. If the lineages of all but one of those sons die out, then the title of Y-MRCA shifts forward from the remaining son through his patrilineal descendants, until

12656-474: Was also at one point considered to be a subspecies, H. s. neanderthalensis . H. heidelbergensis , dated 600,000 to 300,000 years ago, has long been thought to be a likely candidate for the last common ancestor of the Neanderthal and modern human lineages. However, genetic evidence from the Sima de los Huesos fossils published in 2016 seems to suggest that H. heidelbergensis in its entirety should be included in

12769-553: Was that females have a better chance of reproducing than males due to the practice of polygyny . When a male individual has several wives, he has effectively prevented other males in the community from reproducing and passing on their Y chromosomes to subsequent generations. On the other hand, polygyny does not prevent most females in a community from passing on their mitochondrial DNA to subsequent generations. This differential reproductive success of males and females can lead to fewer male lineages relative to female lineages persisting into

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