Chororapithecus abyssinicus
Encyclopedia
Chororapithecus abyssinicus was an ape
that lived about during the Miocene Epoch. It is believed to be the earliest known species
of gorilla
. Its existence indicates that the last common ancestor
between the human
/chimpanzee
lineage
and gorillas may have lived greater than , which is at least 2 million years earlier than the previously thought date of divergence of about 8 million years ago.
The only evidence found of this extinct
ape is currently nine Fossil
ized teeth
of at least three individuals, recovered from the Chorora Formation which runs along the southern Afar Depression
of Ethiopia
(the same place where the remains of Lucy
were discovered in 1974). Analysis of eight molars
(two of them fragmented) and a canine tooth
show that their structure is partly similar to modern gorillas.
The researchers compared the make up of the teeth to other current and fossil apes, and concluded that the new ape fossils possibly were a species of gorilla which ate mostly high-fiber plant
s, and that the fossil species is likely a 'direct ancestor' of the gorillas that currently live in Africa. Alternatively, the idea that the finds are the remains of early hominins has not been ruled out entirely.
from areas in Asia
where fossils from this time period are more plentiful. Molecular estimates that humans and gorillas diverged after 8 million years ago were consistent with this idea, in which an adaptive radiation
might have occurred after a single species entered Africa and began to adapt to different environments.
Current fossils and research prior to this finding indicated that the evolutionary split between gorillas and humans occurred around 8 million years ago. The new fossils indicate that the split may have happened as long as 10.5 million years ago. It is thought that humans shared a common ancestor with chimpanzees as recently as .
. This refers to the calibration of the molecular clock, the average rate of fixation of neutral mutation
s in the human and ape ancestors living in this environment over the past 10 million years. The human-gorilla split could only occur 10 million years ago if the mutations arose five times slower than previously thought, suggesting that other common ancestors of great apes
likewise arose longer ago than believed.
of a genetically different species which consumed similar foods. "It is stretching the evidence to base a time scale for the evolution of the great apes on this new fossil. These structures appear on at least three independent lineages of apes, including gorillas, and they could relate to a dietary shift rather than indicating a new genetic trait," said Professor Peter Andrews at the Natural History Museum
in London
, UK, who also added, "but the fossil evidence for the evolution of our closest living relatives, the great apes, is almost non-existent."
Palaeoanthropologist
Jay Kelley of the University of Illinois at Chicago
was also skeptical
. He remained unconvinced that it was a gorilla, saying that more work would need to be done to determine where this specimen may fit in hominid
evolution
. He said he would be "very cautious" about realigning divergence dates between species based on this specimen.
These teeth are collectively indistinguishable from modern gorilla subspecies in dental size and represented proportions. This modest sample nevertheless exhibits substantial size variation, with molars at both the largest and smallest end of the modern gorilla ranges of variation.
Ape
Apes are Old World anthropoid mammals, more specifically a clade of tailless catarrhine primates, belonging to the biological superfamily Hominoidea. The apes are native to Africa and South-east Asia, although in relatively recent times humans have spread all over the world...
that lived about during the Miocene Epoch. It is believed to be the earliest known species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of gorilla
Gorilla
Gorillas are the largest extant species of primates. They are ground-dwelling, predominantly herbivorous apes that inhabit the forests of central Africa. Gorillas are divided into two species and either four or five subspecies...
. Its existence indicates that the last common ancestor
Common descent
In evolutionary biology, a group of organisms share common descent if they have a common ancestor. There is strong quantitative support for the theory that all living organisms on Earth are descended from a common ancestor....
between the human
Human
Humans are the only living species in the Homo genus...
/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:...
lineage
Lineage (evolution)
An evolutionary lineage is a sequence of species, that form a line of descent, each new species the direct result of speciation from an immediate ancestral species. Lineages are subsets of the evolutionary tree of life. Lineages are often determined by the techniques of molecular systematics.-...
and gorillas may have lived greater than , which is at least 2 million years earlier than the previously thought date of divergence of about 8 million years ago.
The only evidence found of this extinct
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
ape is currently nine Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
ized teeth
Tooth
Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...
of at least three individuals, recovered from the Chorora Formation which runs along the southern Afar Depression
Afar Depression
The Afar Triangle is a geological depression that is caused by the Afar Triple Junction which is part of the Great Rift Valley. It overlaps Eritrea, Djibouti and the entire Afar Region of Ethiopia. The Afar Triangle includes the Danakil Depression and the lowest point in Africa, Lake Asal...
of Ethiopia
Ethiopia
Ethiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...
(the same place where the remains of Lucy
Lucy (Australopithecus)
Lucy is the common name of AL 288-1, several hundred pieces of bone representing about 40% of the skeleton of an individual Australopithecus afarensis. The specimen was discovered in 1974 at Hadar in the Awash Valley of Ethiopia's Afar Depression. Lucy is estimated to have lived 3.2 million years...
were discovered in 1974). Analysis of eight molars
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
(two of them fragmented) and a canine tooth
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...
show that their structure is partly similar to modern gorillas.
The researchers compared the make up of the teeth to other current and fossil apes, and concluded that the new ape fossils possibly were a species of gorilla which ate mostly high-fiber plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s, and that the fossil species is likely a 'direct ancestor' of the gorillas that currently live in Africa. Alternatively, the idea that the finds are the remains of early hominins has not been ruled out entirely.
Previous research
Previous efforts to find fossils of great ape ancestors in Africa from between 12 and 8 million years ago had been largely unsuccessful. This absence led some to hypothesize that apes were absent from Africa during this time, and had recolonized AfricaAfrica
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...
from areas in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
where fossils from this time period are more plentiful. Molecular estimates that humans and gorillas diverged after 8 million years ago were consistent with this idea, in which an adaptive radiation
Adaptive radiation
In evolutionary biology, adaptive radiation is the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage. Starting with a recent single ancestor, this process results in the speciation and phenotypic adaptation of an array of species exhibiting different...
might have occurred after a single species entered Africa and began to adapt to different environments.
Current fossils and research prior to this finding indicated that the evolutionary split between gorillas and humans occurred around 8 million years ago. The new fossils indicate that the split may have happened as long as 10.5 million years ago. It is thought that humans shared a common ancestor with chimpanzees as recently as .
Possible implications
"Based on this fossil, that means the split is much earlier than has been anticipated by the molecular evidence. That means everything has to be put back," said researcher at the Rift Valley Research Service in Ethiopia and a co-author of the study, Berhane AsfawBerhane Asfaw
Berhane Asfaw is an Ethiopian paleontologist of Rift Valley Research Service, who co-discovered human skeletal remains at Herto Bouri, Ethiopia that revealed a transition into modern humans . The specimen was called Homo sapiens idaltu .He graduated from Addis Ababa University in 1980.-References:...
. This refers to the calibration of the molecular clock, the average rate of fixation of neutral mutation
Neutral mutation
In genetics, a neutral mutation is a mutation that has no effect on fitness. In other words, it is neutral with respect to natural selection.For example, some mutations in a DNA triplet or codon do not change which amino acid is introduced: this is known as a synonymous substitution. Unless the...
s in the human and ape ancestors living in this environment over the past 10 million years. The human-gorilla split could only occur 10 million years ago if the mutations arose five times slower than previously thought, suggesting that other common ancestors of great apes
Great Apes
Great Apes may refer to*Great apes, species in the biological family Hominidae, including humans, chimpanzees, gorillas, and orangutans*Great Apes , a 1997 novel by Will Self...
likewise arose longer ago than believed.
Other expert opinions
Despite the finds, other researchers are not convinced that the conclusions are correct. Although the teeth are very similar to those of modern gorillas, they could have been shaped by parallel evolutionParallel evolution
Parallel evolution is the development of a similar trait in related, but distinct, species descending from the same ancestor, but from different clades.-Parallel vs...
of a genetically different species which consumed similar foods. "It is stretching the evidence to base a time scale for the evolution of the great apes on this new fossil. These structures appear on at least three independent lineages of apes, including gorillas, and they could relate to a dietary shift rather than indicating a new genetic trait," said Professor Peter Andrews at the Natural History Museum
Natural History Museum
The Natural History Museum is one of three large museums on Exhibition Road, South Kensington, London, England . Its main frontage is on Cromwell Road...
in London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
, UK, who also added, "but the fossil evidence for the evolution of our closest living relatives, the great apes, is almost non-existent."
Palaeoanthropologist
Paleoanthropology
Paleoanthropology, which combines the disciplines of paleontology and physical anthropology, is the study of ancient humans as found in fossil hominid evidence such as petrifacted bones and footprints.-19th century:...
Jay Kelley of the University of Illinois at Chicago
University of Illinois at Chicago
The University of Illinois at Chicago, or UIC, is a state-funded public research university located in Chicago, Illinois, United States. Its campus is in the Near West Side community area, near the Chicago Loop...
was also skeptical
Skepticism
Skepticism has many definitions, but generally refers to any questioning attitude towards knowledge, facts, or opinions/beliefs stated as facts, or doubt regarding claims that are taken for granted elsewhere...
. He remained unconvinced that it was a gorilla, saying that more work would need to be done to determine where this specimen may fit in hominid
Hominidae
The Hominidae or include them .), as the term is used here, form a taxonomic family, including four extant genera: chimpanzees , gorillas , humans , and orangutans ....
evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
. He said he would be "very cautious" about realigning divergence dates between species based on this specimen.
These teeth are collectively indistinguishable from modern gorilla subspecies in dental size and represented proportions. This modest sample nevertheless exhibits substantial size variation, with molars at both the largest and smallest end of the modern gorilla ranges of variation.
External links
- Researchers find fossils of 10 million-year-old ape at ReutersReutersReuters is a news agency headquartered in New York City. Until 2008 the Reuters news agency formed part of a British independent company, Reuters Group plc, which was also a provider of financial market data...