most recent common ancestor
   HOME

TheInfoList



In
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Development ...

biology
and
genealogy Genealogy (from el, γενεαλογία ' "study of family trees") is the study of , family history, and the tracing of their lineages. Genealogists use oral interviews, historical records, genetic analysis, and other records to obtain inform ...

genealogy
, the most recent common ancestor (MRCA), also known as last common ancestor (LCA), or concestor of a set of
organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), taxonomy into groups such as Multice ...

organism
s is the most recent individual from which all the organisms of the set are descended. The term is also used in reference to the ancestry of groups of
gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance#History, Mendelian units of heredity..." (Greek language, Greek) meaning ''generation'' or ''birth'' ) is a basic unit of her ...

gene
s (
haplotype A haplotype (haploid Ploidy () is the number of complete sets of chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called hi ...
s) rather than organisms. The MRCA of a set of individuals can sometimes be determined by referring to an established
pedigree Pedigree may refer to: Breeding * Pedigree chart, a document to record ancestry, used by genealogists in study of human family lines, and in selective breeding of other animals ** Pedigree, a human genealogy (ancestry chart) ** Pedigree (animal) ...
. However, in general, it is impossible to identify the exact MRCA of a large set of individuals, but an estimate of the time at which the MRCA lived can often be given. Such ''time to most recent common ancestor'' (''TMRCA'') estimates can be given based on DNA test results and established
mutation rate In genetics Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) Though heredity had been observed for millennia, Gregor Mendel, Moravia, Moravian scientist an ...
s as practiced in
genetic genealogy Genetic genealogy is the use of genealogical DNA test A genealogical DNA test is a DNA-based test which looks at specific locations of a person's genome, in order to find or verify ancestral genealogical relationships or (with lower reliabil ...
, or by reference to a non-genetic,
mathematical model A mathematical model is a description of a system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environmen ...
or computer simulation. In organisms using
sexual reproduction Sexual reproduction is a type of reproduction that involves a complex Biological life cycle, life cycle in which a gamete (such as a sperm or egg cell) with a single set of chromosomes (haploid) combines with another to produce a zygote that devel ...
, the ''matrilineal MRCA'' and ''patrilineal MRCA'' are the MRCAs of a given population considering only
matrilineal Matrilineality is the tracing of kinship through the female line. It may also correlate with a social system in which each person is identified with their matriline – their mother's Lineage (anthropology), lineage – and which can inv ...
and
patrilineal Patrilineality, also known as the male line, the spear side or agnatic kinship, is a common kinship system in which an individual's family membership derives from and is recorded through their father's lineage. It generally involves the inheritance ...
descent, respectively. The MRCA of a population by definition cannot be older than either its matrilineal or its patrilineal MRCA. In the case of ''
Homo sapiens Humans (''Homo sapiens'') are the most abundant and widespread of , characterized by and large, complex brains. This has enabled the development of advanced , , and . Humans are highly social and tend to live in complex s composed of many ...

Homo sapiens
'', the matrilineal and patrilineal MRCA are also known as "
Mitochondrial Eve In human genetics Human genetics is the study of inheritance as it occurs in human beings. Human genetics encompasses a variety of overlapping fields including: classical genetics, cytogenetics, molecular genetics Molecular genetics is ...
" (mt-MRCA) and "
Y-chromosomal Adam In human genetics, the Y-chromosomal most recent common ancestor (Y-MRCA, informally known as Y-chromosomal Adam) is the most recent common ancestor (MRCA) from whom all currently living males are descended patrilineally. The term Y-MRCA refle ...
" (Y-MRCA) respectively. The age of the human MRCA is unknown. It is no greater than the age of either the Y-MRCA or the mt-MRCA, estimated at around 200,000 years. Unlike in pedigrees of individual humans or domesticated lineages where historical parentage is known, in the inference of relationships among species or higher groups of
taxa In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanism ...
(
systematics Biological Biology is the natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), or ...
or
phylogenetics In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms ...

phylogenetics
), ancestors are not directly observable or recognizable. They are inferences based on patterns of relationship among taxa inferred in a
phylogenetic analysis In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, ...

phylogenetic analysis
of extant organisms and/or
fossils A fossil (from Classical Latin Classical Latin is the form of Latin language Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the a ...

fossils
. The
last universal common ancestor The last universal common ancestor or last universal cellular ancestor (LUCA), also called the last universal ancestor (LUA), is the most recent population of organisms from which all organisms now living on Earth have a common descent Common ...
(LUCA) is the most recent common ancestor of all current life on Earth, estimated to have lived some 3.5 to 3.8 billion years ago (in the
Paleoarchean The Paleoarchean (), also spelled Palaeoarchaean (formerly known as early Archean), is a geologic era within the Archaean eon. It spans the period of time —the era is defined chronometrically and is not referenced to a specific level of a ...
).


MRCA of different species

The project of a complete description of the phylogenetic relationships among all biological species is dubbed the "
tree of life#REDIRECT Tree of life The tree of life is a fundamental widespread mytheme or archetype in many of the world's mythology, mythologies, religion, religious and philosophy, philosophical traditions. It is closely related to the concept of the s ...
". This involves inference of ages of divergence for all hypothesized
clades A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual cont ...
; for example, the MRCA of all
Carnivora Carnivora is an order of placental Placentalia is one of the three extant subdivisions of the class of animals Mammalia Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch ...
(i.e. the MRCA of "
cat The cat (''Felis catus'') is a domestic Domestic may refer to: In the home * Anything relating to the human home A home, or domicile, is a space used as a permanent or semi-permanent residence for an individual, group or family ...

cat
s and
dog The dog or domestic dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a Domestication, domesticated descendant of the wolf which is characterized by an upturning tail. The dog Origin of the domestic dog, derived from an Pleistocene ...

dog
s") is estimated to have diverged some 42 million years ago (
Miacidae Miacids are extinct primitive carnivoramorphans within the family Miacidae that lived during the Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch ...
). The concept of the last common ancestor from the perspective of
human evolution Human evolution is the evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual re ...

human evolution
is described for a popular audience in ''
The Ancestor's Tale ''The Ancestor's Tale: A Pilgrimage to the Dawn of Life'' is a science book by Richard Dawkins Richard Dawkins (born 26 March 1941) is a British ethologist, evolutionary biologist, atheist thinker, and author An author is the crea ...
'' by
Richard Dawkins Richard Dawkins (born 26 March 1941) is a British evolutionary biologist Evolutionary biology is the subfield of biology that studies the evolutionary processes ( natural selection, common descent, speciation) that produced the Biodiver ...

Richard Dawkins
(2004). Dawkins lists "concestors" of the human lineage in order of increasing age, including
hominin The Hominini form a Tribe (biology), taxonomic tribe of the subfamily Homininae ("hominines"). Hominini includes the extant genera ''Homo'' (humans) and ''Pan (genus), Pan'' (chimpanzees and bonobos), but excludes the genus ''Gorilla'' (gorillas). ...
(human
chimpanzee The chimpanzee (''Pan troglodytes''), also known simply as chimp, is a species of Hominidae, great ape native to the forest and savannah of tropical Africa. It has four confirmed subspecies and a fifth proposed subspecies. The chimpanzee and t ...

chimpanzee
),
hominine Homininae (), also called "African hominids" or "African apes", is a subfamily of Hominidae The Hominidae (), whose members are known as great apes or hominids (), are a taxonomic family of primates that includes eight extant species in fo ...

hominine
(human
gorilla Gorillas are herbivorous File:Land_Snail_radula_tracks.jpg#, 250px, Tracks made by terrestrial gastropods with their radulas, scraping green algae from a surface inside a greenhouse A herbivore is an animal anatomically and physiologica ...

gorilla
),
hominid The Hominidae (), whose members are known as great apes or hominids (), are a taxonomic family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose ...
(human
orangutan Orangutans are Hominidae, great apes native to the rainforests of Indonesia and Malaysia. They are now found only in parts of Borneo and Sumatra, but during the Pleistocene they ranged throughout Southeast Asia and South China. Classified in t ...

orangutan
),
hominoid Apes (Hominoidea ) are a branch Image:Tree Leaves.JPG, The branches and leaves of a tree. A branch ( or , ) or tree branch (sometimes referred to in botany as a ramus) is a woody structural member connected to but not part of the central ...
(human
gibbon Gibbons () are ape Apes (Hominoidea ) are a branch of Old World tailless simians native to Africa and Southeast Asia Southeast Asia or Southeastern Asia is the United Nations geoscheme for Asia#South-eastern Asia, southeastern sub ...

gibbon
), and so on in 40 stages in total, down to the
last universal ancestor The last universal common ancestor or last universal cellular ancestor (LUCA), also called the last universal ancestor (LUA), is the most recent population of organisms from which all organisms now living on Earth have a common descent Commo ...
(human
bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of all known organisms. Cells are the sm ...

bacteria
).


MRCA of a population identified by a single genetic marker

It is also possible to consider the ancestry of individual
gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance#History, Mendelian units of heredity..." (Greek language, Greek) meaning ''generation'' or ''birth'' ) is a basic unit of her ...

gene
s (or groups of genes,
haplotype A haplotype (haploid Ploidy () is the number of complete sets of chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called hi ...
s) instead of an organism as a whole.
Coalescent theory Coalescent theory is a model of how gene variants sampled from a population may have originated from a common ancestor. In the simplest case, coalescent theory assumes no recombination, no natural selection, and no gene flow or population structu ...
describes a stochastic model of how the ancestry of such
genetic marker A genetic marker is a gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance#History, Mendelian units of heredity..." (Greek language, Greek) meaning ''generation'' or ''birth ...
s maps to the history of a population. Unlike organisms, a gene is passed down from a generation of organisms to the next generation either as perfect replicas of itself or as slightly mutated ''descendant genes''. While organisms have ancestry graphs and progeny graphs via
sexual reproduction Sexual reproduction is a type of reproduction that involves a complex Biological life cycle, life cycle in which a gamete (such as a sperm or egg cell) with a single set of chromosomes (haploid) combines with another to produce a zygote that devel ...
, a gene has a single chain of ancestors and a tree of descendants. An organism produced by sexual cross-fertilization (
allogamyAllogamy or cross-fertilization is the fertilization Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual orga ...
) has at least two ancestors (its immediate parents), but a gene always has one ancestor per generation.


Patrilineal and matrilineal MRCA

Mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the located in , cellular s within cells that convert chemical energy from food into a form that cells can use, such as (ATP). Mitochondrial DNA is only a small portion of the DNA in a eukaryotic cell ...

Mitochondrial DNA
(mtDNA) is nearly immune to sexual mixing, unlike the
nuclear DNA Nuclear DNA (nDNA), or nuclear deoxyribonucleic acid, is the DNA contained within each cell nucleus of a eukaryotic organism. It encodes for the majority of the genome in eukaryotes, with mitochondrial DNA Electron microscopy reveals mitoch ...
whose chromosomes are shuffled and recombined in
Mendelian inheritance Mendelian inheritance is a type of biological Biology is the natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific me ...

Mendelian inheritance
. Mitochondrial DNA, therefore, can be used to trace matrilineal inheritance and to find the
Mitochondrial Eve In human genetics Human genetics is the study of inheritance as it occurs in human beings. Human genetics encompasses a variety of overlapping fields including: classical genetics, cytogenetics, molecular genetics Molecular genetics is ...
(also known as the ''African Eve''), the most recent common ancestor of all humans via the mitochondrial DNA pathway. Likewise,
Y chromosome The Y chromosome is one of two sex chromosomes (allosomes) in therian mammals, including humans, and many other animals. The other is the X chromosome. Y is normally the Sex chromosome#Sex determination, sex-determining chromosome in many species, s ...
is present as a single sex chromosome in the male individual and is passed on to male descendants without recombination. It can be used to trace
patrilineal Patrilineality, also known as the male line, the spear side or agnatic kinship, is a common kinship In , kinship is the web of social relationships that form an important part of the lives of all humans in all societies, although its exact ...
inheritance and to find the
Y-chromosomal Adam In human genetics, the Y-chromosomal most recent common ancestor (Y-MRCA, informally known as Y-chromosomal Adam) is the most recent common ancestor (MRCA) from whom all currently living males are descended patrilineally. The term Y-MRCA refle ...
, the most recent common ancestor of all humans via the Y-DNA pathway. Approximate dates for Mitochondrial Eve and Y-chromosomal Adam have been established by researchers using
genealogical DNA test A genealogical DNA test is a DNA The structure of part of a DNA double helix Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist o ...
s. Mitochondrial Eve is estimated to have lived about 200,000 years ago. A paper published in March 2013 determined that, with 95% confidence and that provided there are no
systematic error Observational error (or measurement error) is the difference between a measured value of a quantity and its true value.Dodge, Y. (2003) ''The Oxford Dictionary of Statistical Terms'', OUP. In statistics Statistics is the discipline that co ...
s in the study's data, Y-chromosomal Adam lived between 237,000 and 581,000 years ago. The MRCA of humans alive today would, therefore, need to have lived more recently than either. It is more complicated to infer human ancestry via autosomal chromosomes. Although an autosomal chromosome contains genes that are passed down from parents to children via independent assortment from only one of the two parents, genetic recombination (chromosomal crossover) mixes genes from non-sister chromatids from both parents during meiosis, thus changing the genetic composition of the chromosome.


Time to MRCA estimates

Different types of MRCAs are estimated to have lived at different times in the past. These ''time to MRCA'' (''TMRCA'') estimates are also computed differently depending on the type of MRCA being considered. Patrilineal and matrilineal MRCAs (Mitochondrial Eve and Y-chromosomal Adam) are traced by single gene markers, thus their TMRCA are computed based on DNA test results and established mutation rates as practiced in genetic genealogy. The time to the genealogical MRCA (most recent common ancestor by any line of descent) of all living humans cannot be traced genetically because the DNA of the great majority of ancestors is completely lost after a few hundred years. It is therefore computed based on non-genetic, mathematical models and computer simulations. Since Mitochondrial Eve and Y-chromosomal Adam are traced by single genes via a single ancestral parent line, the time to these genetic MRCAs will necessarily be greater than that for the genealogical MRCA. This is because single genes will coalesce more slowly than tracing of conventional human genealogy via both parents. The latter considers only individual humans, without taking into account whether any gene from the computed MRCA actually survives in every single person in the current population.


TMRCA via genetic markers

Mitochondrial DNA can be used to trace the ancestry of a set of populations. In this case, populations are defined by the accumulation of mutations on the mtDNA, and special trees are created for the mutations and the order in which they occurred in each population. The tree is formed through the testing of a large number of individuals all over the world for the presence or lack of a certain set of mutations. Once this is done it is possible to determine how many mutations separate one population from another. The number of mutations, together with estimated mutation rate of the mtDNA in the regions tested, allows scientists to determine the approximate time to MRCA (''TMRCA'') which indicates time passed since the populations last shared the same set of mutations or belonged to the same haplogroup. In the case of Y-Chromosomal DNA, TMRCA is arrived at in a different way. Human Y-chromosome DNA haplogroup, Y-DNA haplogroups are defined by single-nucleotide polymorphism in various regions of the Y-DNA. The time to MRCA within a haplogroup is defined by the accumulation of mutations in Short tandem repeat, STR sequences of the Y-Chromosome of that haplogroup only. Y-DNA network analysis of Y-STR haplotypes showing a non-star cluster indicates Y-STR variability due to multiple founding individuals. Analysis yielding a star cluster can be regarded as representing a population descended from a single ancestor. In this case the variability of the Y-STR sequence, also called the Microsatellite (genetics), microsatellite variation, can be regarded as a measure of the time passed since the ancestor founded this particular population. The Descent from Genghis Khan, descendants of Genghis Khan or one of his ancestors represents a famous star cluster that can be dated back to the time of Genghis Khan. TMRCA calculations are considered critical evidence when attempting to determine migration dates of various populations as they spread around the world. For example, if a mutation is deemed to have occurred 30,000 years ago, then this mutation should be found amongst all populations that diverged after this date. If archeological evidence indicates cultural spread and formation of regionally isolated populations then this must be reflected in the isolation of subsequent genetic mutations in this region. If genetic divergence and regional divergence coincide it can be concluded that the observed divergence is due to migration as evidenced by the archaeological record. However, if the date of genetic divergence occurs at a different time than the archaeological record, then scientists will have to look at alternate archaeological evidence to explain the genetic divergence. The issue is best illustrated in the debate surrounding the demic diffusion versus cultural diffusion during the Neolithic Europe, European Neolithic.


TMRCA of all living humans

The age of the MRCA of world population, all living humans is unknown. It is necessarily younger than the age of either the matrilinear or the patrilinear MRCA, both of which have an estimated age of between roughly 100,000 and 200,000 years ago. A mathematical, but non-genealogical study by mathematicians Joseph T. Chang, Douglas Rohde and Steve Olson calculated that the MRCA lived remarkably recently, possibly as recently as 300 BCE. This model took into account that people do not truly mate randomly, but that, particularly in the past, people almost always mated with people who lived nearby, and usually with people who lived in their own town or village. It would have been especially rare to mate with somebody who lived in another country. However, Chang et al. found that the rare people who mate with other people far away will in time connect the worldwide family tree, and that no population is truly completely isolated. The MRCA of all humans almost certainly lived in East Asia, which would have given them key access to extremely isolated populations in Australia and the Americas. Possible locations for the MRCA include places such as the Chuckchi and Kamchatka Peninsulas that are close to Alaska, places such as Indonesia and Malaysia that are close to Australia or a place such as Taiwan or Japan that is more intermediate to Australia and the Americas. European colonization of the Americas and Australia was found by Chang to be too recent to have had a substantial impact on the age of the MRCA. In fact, if the Americas and Australia had never been discovered by Europeans, the MRCA would only be about 2.3% further back in the past than it is. Note that the age of the MRCA of a population does not correspond to a population bottleneck, let alone a "first couple". It rather reflects the presence of a single individual with high reproductive success in the past, whose genetic contribution has become pervasive throughout the population over time. It is also incorrect to assume that the MRCA passed all, or indeed any, genetic information to every living person. Through
sexual reproduction Sexual reproduction is a type of reproduction that involves a complex Biological life cycle, life cycle in which a gamete (such as a sperm or egg cell) with a single set of chromosomes (haploid) combines with another to produce a zygote that devel ...
, an ancestor passes half of his or her genes to each descendant in the next generation; after more than 32 generations the contribution of a single ancestor would be on the order of 2−32, a number proportional to less than a single basepair within the human genome.


Identical ancestors point

The MRCA is the most recent ''common'' ancestor shared by all individuals in the population under consideration. This MRCA may well have contemporaries who are also ancestral to some but not all of the extant population. The ''identical ancestors point'' is a point in the past more remote than the MRCA at which time there are no longer organisms which are ancestral to some but not all of the modern population. Due to pedigree collapse, modern individuals may still exhibit clustering, due to vastly different contributions from each of ancestral population.


See also

* Clade, in systematics, a taxonomic group consisting of an ancestral species and all its descendant taxa; or in genetics, an ancestral allele and all its descendant alleles * Cladistics * Common descent *
Coalescent theory Coalescent theory is a model of how gene variants sampled from a population may have originated from a common ancestor. In the simplest case, coalescent theory assumes no recombination, no natural selection, and no gene flow or population structu ...
, a retrospective model of population genetics * Genealogy, the study of families and the tracing of their lineages and history * Genetic distance, the genetic divergence between species or between populations within a species * Genetic genealogy, the application of genetics to genealogy, traditional genealogy * Genealogical DNA tests, examination of nucleotides at specific locations on a person's DNA for genetic genealogy purposes * Last universal common ancestor, the most recent common ancestor of all life on Earth * Lowest common ancestor, an analogous concept in graph theory and computer science * Pedigree collapse * Phylogenetic tree, a branching diagram or "tree" showing the inferred evolutionary relationships among various biological species * Timeline of evolution, outlines the major events in the development of life on the planet Earth * Timeline of human evolution, outlines the major events in the development of the human species


Notes


References


Further reading

* * {{DEFAULTSORT:Most Recent Common Ancestor Evolutionary biology Genetic genealogy Genealogy Phylogenetics Population genetics Last common ancestors