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Molecular anthropology
Molecular anthropology, also known as genetic anthropology, is the study of how molecular biology has contributed to the understanding of human evolution. This field of anthropology examines evolutionary links between ancient and modern human populations, as well as between contemporary species. Generally, comparisons are made between sequences, either DNA or protein sequences; however, early studies used comparative serology.
By examining DNA sequences in different populations, scientists can determine the closeness of relationships between populations (or within populations). Certain similarities in genetic makeup let molecular anthropologists determine whether or not different groups of people belong to the same haplogroup, and thus if they share a common geographical origin. This is significant because it allows anthropologists to trace patterns of migration and settlement, which gives helpful insight as to how contemporary populations have formed and progressed over time.
Molecular anthropology has been extremely useful in establishing the evolutionary tree of humans and other primates, including closely related species like chimps and gorillas. While there are clearly a number of morphological similarities between humans and chimpanzees, for example, certain studies also have concluded that there is roughly a 98 percent commonality between the DNA of both species. [citation needed] However, more recent studies have modified the commonality of 98 percent to a commonality of 94 percent, showing that the genetic gap between humans and chimps is larger than originally thought. Such information is useful in searching for common ancestors and coming to a better understanding of how humans evolved.
There are two continuous linkage groups in humans that are carried by a single sex. The first is the Y chromosome, which is passed from father to son. Anatomical females carry a Y chromosome only rarely, as a result of genetic defect. The other linkage group is the mitochondrial DNA (mtDNA). MtDNA is almost always only passed to the next generation by females, but under highly exceptional circumstances mtDNA can be passed through males.[clarification needed] The non-recombinant portion of the Y chromosome and the mtDNA, under normal circumstances, do not undergo productive recombination. Part of the Y chromosome can undergo recombination with the X chromosome and within ape history the boundary has changed. Such recombinant changes in the non-recombinant region of Y are extremely rare.[citation needed]
Mitochondrial DNA became an area of research in phylogenetics in the late 1970s. Unlike genomic DNA, it offered advantages in that it did not undergo recombination. The process of recombination, if frequent enough, corrupts the ability to create parsimonious trees because of stretches of amino acid subsititions (SNPs).[clarification needed] When looking between distantly related species, recombination is less of a problem since recombination between branches from common ancestors is prevented after true speciation occurs. When examining closely related species, or branching within species, recombination creates a large number of 'irrelevant SNPs' for cladistic analysis. MtDNA, through the process of organelle division, became clonal over time; very little, or often none, of that paternal mtDNA is passed. While recombination may occur in mtDNA, there is little risk that it will be passed to the next generation. As a result, mtDNA become clonal copies of each other, except when a new mutation arises. As a result, mtDNA does not have pitfalls of autosomal loci when studied in interbreeding groups. Another advantage of mtDNA is that the hyper-variable regions evolve quickly; this shows that certain regions of mitochondrial DNA approach neutrality. This allowed the use of mitochondrial DNA to determine that the relative age of the human population was small, having gone through a recent constriction at about 150,000 years ago (see #Causes of errors).
Mitochondrial DNA has also been used to verify the proximity of chimpanzees to humans relative to gorillas, and to verify the relationship of these three species relative to the orangutans.
More recently,[when?] the mtDNA genome has been used to estimate branching patterns in peoples around the world, such as when the new world was settled and how. The problem with these studies have been that they rely heavily on mutations in the coding region. Researchers have increasingly discovered that as humans moved from Africa's south-eastern regions, that more mutations accumulated in the coding region than expected, and in passage to the new world some groups are believed[citation needed] to have passed from the Asian tropics to Siberia to an ancient land region called Beringia and quickly migrated to South America. Many of the mtDNA have far more mutations and at rarely mutated coding sites relative to expectations of neutral mutations.
Mitochondrial DNA offers another advantage over autosomal DNA. There are generally 2 to 4 copies of each chromosome in each cell (1 to 2 from each parent chromosome). For mtDNA there can be dozens to hundreds in each cell. This increases the amount of each mtDNA loci by at least a magnitude. For ancient DNA, in which the DNA is highly degraded, the number of copies of DNA is helpful in extending and bridging short fragments together, and decreases the amount of bone extracted from highly valuable fossil/ancient remains. Unlike Y chromosome, both male and female remains carry mtDNA in roughly equal quantities.
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Molecular anthropology
Molecular anthropology, also known as genetic anthropology, is the study of how molecular biology has contributed to the understanding of human evolution. This field of anthropology examines evolutionary links between ancient and modern human populations, as well as between contemporary species. Generally, comparisons are made between sequences, either DNA or protein sequences; however, early studies used comparative serology.
By examining DNA sequences in different populations, scientists can determine the closeness of relationships between populations (or within populations). Certain similarities in genetic makeup let molecular anthropologists determine whether or not different groups of people belong to the same haplogroup, and thus if they share a common geographical origin. This is significant because it allows anthropologists to trace patterns of migration and settlement, which gives helpful insight as to how contemporary populations have formed and progressed over time.
Molecular anthropology has been extremely useful in establishing the evolutionary tree of humans and other primates, including closely related species like chimps and gorillas. While there are clearly a number of morphological similarities between humans and chimpanzees, for example, certain studies also have concluded that there is roughly a 98 percent commonality between the DNA of both species. [citation needed] However, more recent studies have modified the commonality of 98 percent to a commonality of 94 percent, showing that the genetic gap between humans and chimps is larger than originally thought. Such information is useful in searching for common ancestors and coming to a better understanding of how humans evolved.
There are two continuous linkage groups in humans that are carried by a single sex. The first is the Y chromosome, which is passed from father to son. Anatomical females carry a Y chromosome only rarely, as a result of genetic defect. The other linkage group is the mitochondrial DNA (mtDNA). MtDNA is almost always only passed to the next generation by females, but under highly exceptional circumstances mtDNA can be passed through males.[clarification needed] The non-recombinant portion of the Y chromosome and the mtDNA, under normal circumstances, do not undergo productive recombination. Part of the Y chromosome can undergo recombination with the X chromosome and within ape history the boundary has changed. Such recombinant changes in the non-recombinant region of Y are extremely rare.[citation needed]
Mitochondrial DNA became an area of research in phylogenetics in the late 1970s. Unlike genomic DNA, it offered advantages in that it did not undergo recombination. The process of recombination, if frequent enough, corrupts the ability to create parsimonious trees because of stretches of amino acid subsititions (SNPs).[clarification needed] When looking between distantly related species, recombination is less of a problem since recombination between branches from common ancestors is prevented after true speciation occurs. When examining closely related species, or branching within species, recombination creates a large number of 'irrelevant SNPs' for cladistic analysis. MtDNA, through the process of organelle division, became clonal over time; very little, or often none, of that paternal mtDNA is passed. While recombination may occur in mtDNA, there is little risk that it will be passed to the next generation. As a result, mtDNA become clonal copies of each other, except when a new mutation arises. As a result, mtDNA does not have pitfalls of autosomal loci when studied in interbreeding groups. Another advantage of mtDNA is that the hyper-variable regions evolve quickly; this shows that certain regions of mitochondrial DNA approach neutrality. This allowed the use of mitochondrial DNA to determine that the relative age of the human population was small, having gone through a recent constriction at about 150,000 years ago (see #Causes of errors).
Mitochondrial DNA has also been used to verify the proximity of chimpanzees to humans relative to gorillas, and to verify the relationship of these three species relative to the orangutans.
More recently,[when?] the mtDNA genome has been used to estimate branching patterns in peoples around the world, such as when the new world was settled and how. The problem with these studies have been that they rely heavily on mutations in the coding region. Researchers have increasingly discovered that as humans moved from Africa's south-eastern regions, that more mutations accumulated in the coding region than expected, and in passage to the new world some groups are believed[citation needed] to have passed from the Asian tropics to Siberia to an ancient land region called Beringia and quickly migrated to South America. Many of the mtDNA have far more mutations and at rarely mutated coding sites relative to expectations of neutral mutations.
Mitochondrial DNA offers another advantage over autosomal DNA. There are generally 2 to 4 copies of each chromosome in each cell (1 to 2 from each parent chromosome). For mtDNA there can be dozens to hundreds in each cell. This increases the amount of each mtDNA loci by at least a magnitude. For ancient DNA, in which the DNA is highly degraded, the number of copies of DNA is helpful in extending and bridging short fragments together, and decreases the amount of bone extracted from highly valuable fossil/ancient remains. Unlike Y chromosome, both male and female remains carry mtDNA in roughly equal quantities.