Chimpanzee-human last common ancestor
Encyclopedia
The chimpanzee-human last common ancestor (CHLCA, CLCA, or C/H LCA) is the last species, a species of African apes, that human
s, bonobo
s and chimpanzee
s share as a common ancestor.
The CHLCA is generally used as an anchor point for calculating single-nucleotide polymorphism (SNP) rates in human genetic studies where chimpanzees are used as an outgroup. The CHLCA is frequently cited as an anchor for molecular TMRCA (Time to most recent common ancestor
) determination because the two species of the genus pan, the Bonobos and the Chimpanzee, are the species most genetically similar to Homo sapiens.
, and Orrorin tugenensis
are closest in age and expected morphology of the CHLCA and suggest the LCA is older than 7 million years. Earliest studies of apes suggest the CHLCA may have been as old as 25 million years, however protein studies in the 1970s suggested the CHLCA was less than 8 million years in age. Genetic methods based on Orangutan/Human and Gibbon/Human LCA times have then been used to estimate Chimpanzee/Human LCA of 6 million years and LCA times between 5 and 7 million years are currently used in the literature.Studies have pointed to the slowing molecular clock as monkeys evolved into apes and apes evolved into humans. In particular Macaque mtDNA is evolved 30% more rapidly than African Ape mtDNA.
Because chimps and humans share a matrilineal ancestor, establishing the geological age of that last ancestor allows the estimation of the mutation rate. However, fossil
s of the exact last common ancestor would be an extremely rare find. The CHLCA is frequently cited as an anchor for mt-TMRCA determination because chimpanzees are the species most genetically similar to humans. However, there are no known fossils that represent that CHLCA. It is believed that there are no proto-chimpanzee fossils or proto-gorilla fossils that have been clearly identified. However, Richard Dawkins in his book "The Ancestor's tale" proposes that robust Australopithecines: Paranthropus, are the ancestors of gorillas, whereas some of the gracile australopithecus are the ancestors of chimpanzees (see Homininae
).
Some researchers tried to estimate the age of the CHLCA (TCHLCA) using biopolymer structures
which differ slightly between closely related animals. Among these researchers, Allan C. Wilson and Vincent Sarich
were pioneers in the development of the molecular clock for humans. Working on protein sequence
s they eventually determined that apes were closer to humans than some paleontologists perceived based on the fossil record."If man and old world monkeys last shared a common ancestor 30 million years ago, then man and African apes shared a common ancestor 5 million years ago..." Later Vincent Sarich concluded that the TCHLCA was no greater than 8 million years in age, with a favored range between 4 and 6 million years before present.
This paradigmatic age has stuck with molecular anthropology until the late 1990s, when others began questioning the certainty of the assumption. Currently, the estimation of the TCHLCA is less certain, and there is genetic as well as paleontological support for increasing TCHLCA. A 13 million year TCHLCA is one proposed age.
for the last common ancestor of humans (Homo sapiens) and chimpanzees (Pan troglodytes). This species is supposed, on the basis of DNA
reconstruction (no fossil remains have been found), to have existed prior to six million years ago, when the human
and chimpanzee
lines are thought to have diverged. Pan prior lived an arboreal existence in the forests of Africa
. It was initially thought that an Ice Age
, around seven million years ago, caused forests to shrink thus prompting some members of the species to venture into the savannah, becoming the ancestors of humanity. However, the discovery of Ardipithecus ramidus shows that bipedal locomotion was used both on the ground and in the trees around 4.4 million years ago. Researchers infer from the form of her pelvis and limbs and the presence of her abductable hallux
, that she was a Facultative biped
: bipedal when moving on the ground, but quadrupedal when moving about in tree branches.
Human
Humans are the only living species in the Homo genus...
s, bonobo
Bonobo
The bonobo , Pan paniscus, previously called the pygmy chimpanzee and less often, the dwarf or gracile chimpanzee, is a great ape and one of the two species making up the genus Pan. The other species in genus Pan is Pan troglodytes, or the common chimpanzee...
s and chimpanzee
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...
s share as a common ancestor.
The CHLCA is generally used as an anchor point for calculating single-nucleotide polymorphism (SNP) rates in human genetic studies where chimpanzees are used as an outgroup. The CHLCA is frequently cited as an anchor for molecular TMRCA (Time to most recent common ancestor
Most recent common ancestor
In genetics, the most recent common ancestor of any set of organisms is the most recent individual from which all organisms in the group are directly descended...
) determination because the two species of the genus pan, the Bonobos and the Chimpanzee, are the species most genetically similar to Homo sapiens.
Time estimates
The age of the CHLCA is an estimate. The fossil find of Ardipithecus kadabba, Sahelanthropus tchadensisSahelanthropus tchadensis
Sahelanthropus tchadensis is an extinct hominid species that is dated to about . Whether it can be regarded as part of the Hominina tree is unclear; there are arguments both supporting and rejecting it...
, and Orrorin tugenensis
Orrorin tugenensis
Orrorin tugenensis is considered to be the second-oldest known hominin ancestor that is possibly related to modern humans, and it is the only species classified in genus Orrorin...
are closest in age and expected morphology of the CHLCA and suggest the LCA is older than 7 million years. Earliest studies of apes suggest the CHLCA may have been as old as 25 million years, however protein studies in the 1970s suggested the CHLCA was less than 8 million years in age. Genetic methods based on Orangutan/Human and Gibbon/Human LCA times have then been used to estimate Chimpanzee/Human LCA of 6 million years and LCA times between 5 and 7 million years are currently used in the literature.Studies have pointed to the slowing molecular clock as monkeys evolved into apes and apes evolved into humans. In particular Macaque mtDNA is evolved 30% more rapidly than African Ape mtDNA.
Because chimps and humans share a matrilineal ancestor, establishing the geological age of that last ancestor allows the estimation of the mutation rate. However, fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s of the exact last common ancestor would be an extremely rare find. The CHLCA is frequently cited as an anchor for mt-TMRCA determination because chimpanzees are the species most genetically similar to humans. However, there are no known fossils that represent that CHLCA. It is believed that there are no proto-chimpanzee fossils or proto-gorilla fossils that have been clearly identified. However, Richard Dawkins in his book "The Ancestor's tale" proposes that robust Australopithecines: Paranthropus, are the ancestors of gorillas, whereas some of the gracile australopithecus are the ancestors of chimpanzees (see Homininae
Homininae
Homininae is a subfamily of Hominidae, which includes humans, gorillas and chimpanzees, and some extinct relatives; it comprises all those hominids, such as Australopithecus, that arose after the split from orangutans . Our family tree, which has 3 main branches leading to chimpanzees, humans and...
).
Some researchers tried to estimate the age of the CHLCA (TCHLCA) using biopolymer structures
Biopolymer
Biopolymers are polymers produced by living organisms. Since they are polymers, Biopolymers contain monomeric units that are covalently bonded to form larger structures. There are three main classes of biopolymers based on the differing monomeric units used and the structure of the biopolymer formed...
which differ slightly between closely related animals. Among these researchers, Allan C. Wilson and Vincent Sarich
Vincent Sarich
- Biography :Born in Chicago, he received a bachelor of science in chemistry from Illinois Institute of Technology and his masters and doctorate in anthropology from University of California, Berkeley...
were pioneers in the development of the molecular clock for humans. Working on protein sequence
Peptide sequence
Peptide sequence or amino acid sequence is the order in which amino acid residues, connected by peptide bonds, lie in the chain in peptides and proteins. The sequence is generally reported from the N-terminal end containing free amino group to the C-terminal end containing free carboxyl group...
s they eventually determined that apes were closer to humans than some paleontologists perceived based on the fossil record."If man and old world monkeys last shared a common ancestor 30 million years ago, then man and African apes shared a common ancestor 5 million years ago..." Later Vincent Sarich concluded that the TCHLCA was no greater than 8 million years in age, with a favored range between 4 and 6 million years before present.
This paradigmatic age has stuck with molecular anthropology until the late 1990s, when others began questioning the certainty of the assumption. Currently, the estimation of the TCHLCA is less certain, and there is genetic as well as paleontological support for increasing TCHLCA. A 13 million year TCHLCA is one proposed age.
Pan Prior
Pan prior is the name suggested by British biological anthropologist Richard WranghamRichard Wrangham
Richard W. Wrangham is a British primatologist. He is the Ruth Moore Professor of Biological Anthropology at Harvard University and his research group is now part of the newly established Department of Human Evolutionary Biology....
for the last common ancestor of humans (Homo sapiens) and chimpanzees (Pan troglodytes). This species is supposed, on the basis of DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
reconstruction (no fossil remains have been found), to have existed prior to six million years ago, when the human
Human
Humans are the only living species in the Homo genus...
and chimpanzee
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...
lines are thought to have diverged. Pan prior lived an arboreal existence in the forests of Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. It was initially thought that an Ice Age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
, around seven million years ago, caused forests to shrink thus prompting some members of the species to venture into the savannah, becoming the ancestors of humanity. However, the discovery of Ardipithecus ramidus shows that bipedal locomotion was used both on the ground and in the trees around 4.4 million years ago. Researchers infer from the form of her pelvis and limbs and the presence of her abductable hallux
Hallux
In tetrapods, the hallux is the innermost toe of the foot. Despite its name it may not be the longest toe on the foot of some individuals...
, that she was a Facultative biped
Facultative biped
A facultative biped is an animal that is capable of walking or running on two legs, often for only a limited period of time, in spite of normally walking or running on four limbs or more. Well-known examples include many lizards such as the Basilisk lizard, and even some cockroaches when running...
: bipedal when moving on the ground, but quadrupedal when moving about in tree branches.
See also
- Ardipithecus ramidus
- AustralopithecusAustralopithecusAustralopithecus is a genus of hominids that is now extinct. From the evidence gathered by palaeontologists and archaeologists, it appears that the Australopithecus genus evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct...
- HomininaeHomininaeHomininae is a subfamily of Hominidae, which includes humans, gorillas and chimpanzees, and some extinct relatives; it comprises all those hominids, such as Australopithecus, that arose after the split from orangutans . Our family tree, which has 3 main branches leading to chimpanzees, humans and...
- Human evolutionHuman evolutionHuman evolution refers to the evolutionary history of the genus Homo, including the emergence of Homo sapiens as a distinct species and as a unique category of hominids and mammals...
- Human evolutionary geneticsHuman evolutionary geneticsHuman evolutionary genetics studies how one human genome differs from the other, the evolutionary past that gave rise to it, and its current effects. Differences between genomes have anthropological, medical and forensic implications and applications...
- HumanzeeHumanzeeThe humanzee is a hypothetical chimpanzee/human hybrid. Chimpanzees and humans are closely related , leading to contested speculation that a hybrid is possible, though no specimen has ever been confirmed.-Etymology:In spite of the usual convention of portmanteau...
- Timeline of human evolutionTimeline of human evolutionThe timeline of human evolution outlines the major events in the development of human species, and the evolution of humans' ancestors. It includes a brief explanation of some animals, species or genera, which are possible ancestors of Homo sapiens...