Australopithecus sediba
Encyclopedia
Australopithecus sediba is a species of Australopithecus
of the early Pleistocene
, identified based on fossil remains dated to about 2 million years ago.
The species is known from at least four partial skeletons discovered in the Malapa Fossil Site
at the Cradle of Humankind
World Heritage Site
in South Africa
, one a juvenile male (MH1, the holotype
), an adult female (MH2), at least one other adult and an 18-month-old infant.
The MH1 and MH2 fossils were buried together, and have been dated to between 1.977 and 1.980 million years ago.
Over two hundred and twenty fragments from the species have been recovered to date. The partial skeletons were initially described in two papers in the journal Science
by American and South African palaeo-anthropologist Lee R. Berger
and colleagues as a newly discovered species of early human ancestor called Australopithecus sediba ("sediba" meaning "natural spring" or "well" in the Sotho language).
, on the Malapa Nature Reserve, Matthew stumbled upon a fossilized bone. The boy alerted his father of the find, who could not believe what he saw, a hominid clavicle and upon turning the block over; "sticking out of the back of the rock was a mandible with a tooth, a canine, sticking out. And I almost died", he later recalled. The fossil turned out to belong to a juvenile male, the skull of which was discovered in March 2009 by Berger's team. The find was announced to the public on April 8, 2010.
Also found at the Malapa archeological site
were a variety of animal fossils, including saber-toothed cat
s, mongooses, and antelopes. Berger and geologist Paul Dirks speculated that the animals might have fallen into a deep, 100–150 ft (30.5–45.7 m) "death-trap", perhaps lured by the scent of water. The bodies may have then been swept into a pool of water rich with lime, and with sand at the bottom, making it possible for the remains to become fossilized.
and uranium-lead (U-Pb) dating
by Andy Herries (La Trobe University
, Australia), Robyn Pickering (U. Melbourne, Australia) and Jan Kramers (U. Johannesburg). U-Pb dating of the underlying flowstone indicates that the fossils are not older than ~2.0 Ma. The occurrence of species of animal that became extinct at ~1.5 Ma indicate the deposit is not younger than 1.5 Ma. The sediments have a 'normal' magnetic polarity and the only major period between 2.0 and 1.5 Ma when this occurred is the Olduvai sub-Chron between 1.95 and 1.78 Ma. As such, the fossils were originally dated to ~1.95 Ma. Recent dating of a capping flowstone illustrated this was not possible and the normal magnetic polarity sediments have since been correlated to the 3000 year long Pre-Olduvai event at ~1.977 Ma.
(the Taung Child
, Mrs. Ples
) and either Homo habilis
or even the later H. erectus
(Turkana boy
, Java man
, Peking man
). The cranial capacity of MH1, which has been estimated to be at 95% of adult capacity (420 ml/cc), is at the higher end of the range for A. africanus and far from the lower range of early Homo (631 ml/cc), but the mandible and tooth size are quite gracile and similar to what one would expect to find in H. erectus, so similar that if found in isolation without other skeletal remains could be classified as Homo based on tooth and mandible size. However, the cusp spacing is more like Australopithecus. Another interesting example of the wide range of interspecific variation of this species is that although MH2 is an adult, the tooth size of MH1, the juvenile, is larger than that of the adult. At the same time in Africa were the Homo ergaster (or early H. erectus) with a more human morphology and a larger cranial capacity (700-900cm³ ).
Regardless of whether Australopithecus sediba is an ancestor of early Homo or not, our understanding of the range of variation in early hominins has been greatly increased with the finding of these new specimens.
A. sediba compared to its ancestor species A. africanus on the whole is described by Berger et al. as more derived towards Homo than A. garhi
, especially showing a number of synapomorphies
taken to anticipate the reorganization of the pelvis
in H. erectus, associated with "more energetically efficient walking and running". The femur and tibia are fragmentary and the foot is more primitive. Its cranial capacity
is estimated at around 420 –, about one-third that of modern humans.
A. sediba had a surprisingly modern hand, whose precision grip suggests it might have been another tool-making Australopithecus .
As opposed to the authors of the initial description, who interpreted both fossils as a possible transitional species between Australopithecus and Homo, other palaeoanthropologists are reluctant to do so. In an accompanying news article published with the initial descriptions in 2010, detractors of the idea that "Au. sediba" might be ancestral to the genus "Homo" (e.g. Tim White and Ron Clarke
) suggest that the fossils could be a late southern African branch of Australopithecus
, co-existing with already existing members of the Homo genus. This interpretation is based on the observation that the lower jaw, discovered by Friedemann Schrenk, of a 2.5 million year old fossil attributed to H. rudolfensis
is the oldest known fossil ascribed to the Homo genus. This specimen is thus presumed to be older than the Australopithecus sediba fossils. The critics, however continue to ascribe to A. africanus the status of precursor of the Homo genus. Criticism has been raised in a news report on the find in Nature
magazine that the authors of the initial description have failed to take the wealth of variation within A. africanus into account, prior to defining the finds as an independent species. Additionally, the basing of the description of the species largely on the skeleton of a juvenile specimen has been subject to criticism, given that there is no certain way of saying to what extent adults would differ from juvenile specimens. This has been a common practice in palaeoanthropology, with even the type specimens of Homo habilis
and Australopithecus africanus
being juvenile specimens.
Australopithecus
Australopithecus 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...
of the early Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
, identified based on fossil remains dated to about 2 million years ago.
The species is known from at least four partial skeletons discovered in the Malapa Fossil Site
Malapa Fossil Site, Cradle of Humankind
Malapa is a fossil-bearing cave located about Northeast of the well known South African hominid-bearing sites of Sterkfontein and Swartkrans and about North-Northwest of the City of Johannesburg, South Africa...
at the Cradle of Humankind
Cradle of Humankind
The Cradle of Humankind is a World Heritage Site first named by UNESCO in 1999, about 50 kilometres northwest of Johannesburg, South Africa in the Gauteng province. This site currently occupies ; it contains a complex of limestone caves, including the Sterkfontein Caves, where the 2.3-million...
World Heritage Site
World Heritage Site
A UNESCO World Heritage Site is a place that is listed by the UNESCO as of special cultural or physical significance...
in South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, one a juvenile male (MH1, the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
), an adult female (MH2), at least one other adult and an 18-month-old infant.
The MH1 and MH2 fossils were buried together, and have been dated to between 1.977 and 1.980 million years ago.
Over two hundred and twenty fragments from the species have been recovered to date. The partial skeletons were initially described in two papers in the journal Science
Science (journal)
Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....
by American and South African palaeo-anthropologist Lee R. Berger
Lee R. Berger
Lee Rogers Berger is a paleoanthropologist, physical anthropologist and archeologist and is best known for his discovery of Australopithecus sediba and his work on Australopithecus africanus body proportions and the Taung Bird of Prey Hypothesis.-Background:Berger was born in Shawnee Mission,...
and colleagues as a newly discovered species of early human ancestor called Australopithecus sediba ("sediba" meaning "natural spring" or "well" in the Sotho language).
Discovery
The first specimen of A. sediba was found by paleoanthropologist Lee Berger's nine-year-old son, Matthew, on August 15, 2008. While exploring near his father's dig site in the dolomitic hills north of JohannesburgJohannesburg
Johannesburg also known as Jozi, Jo'burg or Egoli, is the largest city in South Africa, by population. Johannesburg is the provincial capital of Gauteng, the wealthiest province in South Africa, having the largest economy of any metropolitan region in Sub-Saharan Africa...
, on the Malapa Nature Reserve, Matthew stumbled upon a fossilized bone. The boy alerted his father of the find, who could not believe what he saw, a hominid clavicle and upon turning the block over; "sticking out of the back of the rock was a mandible with a tooth, a canine, sticking out. And I almost died", he later recalled. The fossil turned out to belong to a juvenile male, the skull of which was discovered in March 2009 by Berger's team. The find was announced to the public on April 8, 2010.
Also found at the Malapa archeological site
Malapa Fossil Site, Cradle of Humankind
Malapa is a fossil-bearing cave located about Northeast of the well known South African hominid-bearing sites of Sterkfontein and Swartkrans and about North-Northwest of the City of Johannesburg, South Africa...
were a variety of animal fossils, including saber-toothed cat
Saber-toothed cat
Saber-toothed cat or Sabre-toothed cat refers to the extinct subfamilies of Machairodontinae , Barbourofelidae , and Nimravidae as well as two families related to marsupials that were found worldwide from the Eocene Epoch to the end of the Pleistocene Epoch ,...
s, mongooses, and antelopes. Berger and geologist Paul Dirks speculated that the animals might have fallen into a deep, 100–150 ft (30.5–45.7 m) "death-trap", perhaps lured by the scent of water. The bodies may have then been swept into a pool of water rich with lime, and with sand at the bottom, making it possible for the remains to become fossilized.
Age estimates
The fossil was dated using a combination of palaeomagnetismArchaeomagnetic dating
Archaeomagnetic dating is the study and interpretation of the signatures of the Earth's magnetic field at past times recorded in archaeological materials. These paleomagnetic signatures are fixed when ferromagnetic materials such as magnetite cool below the Curie point, freezing the magnetic moment...
and uranium-lead (U-Pb) dating
Uranium-lead dating
Uranium-lead is one of the oldest and most refined of the radiometric dating schemes, with a routine age range of about 1 million years to over 4.5 billion years, and with routine precisions in the 0.1-1 percent range...
by Andy Herries (La Trobe University
La Trobe University
La Trobe University is a multi-campus university in Victoria, Australia. It was established in 1964 by an Act of Parliament to become the third oldest university in the state of Victoria. The main campus of La Trobe is located in the Melbourne suburb of Bundoora; two other major campuses are...
, Australia), Robyn Pickering (U. Melbourne, Australia) and Jan Kramers (U. Johannesburg). U-Pb dating of the underlying flowstone indicates that the fossils are not older than ~2.0 Ma. The occurrence of species of animal that became extinct at ~1.5 Ma indicate the deposit is not younger than 1.5 Ma. The sediments have a 'normal' magnetic polarity and the only major period between 2.0 and 1.5 Ma when this occurred is the Olduvai sub-Chron between 1.95 and 1.78 Ma. As such, the fossils were originally dated to ~1.95 Ma. Recent dating of a capping flowstone illustrated this was not possible and the normal magnetic polarity sediments have since been correlated to the 3000 year long Pre-Olduvai event at ~1.977 Ma.
Morphology and interpretations
Because of the wide range of mosaic features exhibited in both cranial and post cranial morphology, the authors suggest that A. sediba may be a transitional species between the southern African A. africanusAustralopithecus africanus
Australopithecus africanus was an early hominid, an australopithecine, who lived between 2–3 million years ago in the Pliocene. In common with the older Australopithecus afarensis, A. africanus was slenderly built, or gracile, and was thought to have been a direct ancestor of modern humans. Fossil...
(the Taung Child
Taung Child
The Taung Child — or Taung Baby — is the fossilized skull of a young Australopithecus africanus individual. It was discovered in 1924 by quarrymen working for the Northern Lime Company in Taung, South Africa...
, Mrs. Ples
Mrs. Ples
Mrs. Ples is the popular nickname for the most complete skull of an Australopithecus africanus specimen ever found in South Africa. Many fossils of this species, which are considered to be the distant relatives of all humankind, have been found in the Sterkfontein area, in what has been designated...
) and either Homo habilis
Homo habilis
Homo habilis is a species of the genus Homo, which lived from approximately at the beginning of the Pleistocene period. The discovery and description of this species is credited to both Mary and Louis Leakey, who found fossils in Tanzania, East Africa, between 1962 and 1964. Homo habilis Homo...
or even the later H. erectus
Homo erectus
Homo erectus is an extinct species of hominid that lived from the end of the Pliocene epoch to the later Pleistocene, about . The species originated in Africa and spread as far as India, China and Java. There is still disagreement on the subject of the classification, ancestry, and progeny of H...
(Turkana boy
Turkana Boy
Turkana Boy, also occasionally, Nariokotome Boy is the common name of fossil KNM-WT 15000, a nearly complete skeleton of a hominid who died in the early Pleistocene. This specimen is the most complete early human skeleton ever found. It is 1.5 million years old...
, Java man
Java Man
Java Man is the name given to fossils discovered in 1891 at Trinil - Ngawi Regency on the banks of the Solo River in East Java, Indonesia, one of the first known specimens of Homo erectus...
, Peking man
Peking Man
Peking Man , Homo erectus pekinensis, is an example of Homo erectus. A group of fossil specimens was discovered in 1923-27 during excavations at Zhoukoudian near Beijing , China...
). The cranial capacity of MH1, which has been estimated to be at 95% of adult capacity (420 ml/cc), is at the higher end of the range for A. africanus and far from the lower range of early Homo (631 ml/cc), but the mandible and tooth size are quite gracile and similar to what one would expect to find in H. erectus, so similar that if found in isolation without other skeletal remains could be classified as Homo based on tooth and mandible size. However, the cusp spacing is more like Australopithecus. Another interesting example of the wide range of interspecific variation of this species is that although MH2 is an adult, the tooth size of MH1, the juvenile, is larger than that of the adult. At the same time in Africa were the Homo ergaster (or early H. erectus) with a more human morphology and a larger cranial capacity (700-900cm³ ).
Regardless of whether Australopithecus sediba is an ancestor of early Homo or not, our understanding of the range of variation in early hominins has been greatly increased with the finding of these new specimens.
A. sediba compared to its ancestor species A. africanus on the whole is described by Berger et al. as more derived towards Homo than A. garhi
Australopithecus garhi
Australopithecus garhi is a gracile australopithecine species whose fossils were discovered in 1996 by a research team led by Ethiopian paleontologist Berhane Asfaw and Tim White, an American paleontologist. The hominin remains are believed to be a human ancestor species and the final missing link...
, especially showing a number of synapomorphies
Synapomorphy
In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...
taken to anticipate the reorganization of the pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
in H. erectus, associated with "more energetically efficient walking and running". The femur and tibia are fragmentary and the foot is more primitive. Its cranial capacity
Cranial capacity
Cranial capacity is a measure of the volume of the interior of the cranium of those vertebrates who have both a cranium and a brain. The most commonly used unit of measure is the cubic centimetre or cc...
is estimated at around 420 –, about one-third that of modern humans.
A. sediba had a surprisingly modern hand, whose precision grip suggests it might have been another tool-making Australopithecus .
As opposed to the authors of the initial description, who interpreted both fossils as a possible transitional species between Australopithecus and Homo, other palaeoanthropologists are reluctant to do so. In an accompanying news article published with the initial descriptions in 2010, detractors of the idea that "Au. sediba" might be ancestral to the genus "Homo" (e.g. Tim White and Ron Clarke
Ronald J. Clarke
Ronald J. Clarke is a paleoanthropologist most notable for the discovery of "Little Foot", an extraordinary complete skeleton of Australopithecus, in the Sterkfontein Caves...
) suggest that the fossils could be a late southern African branch of Australopithecus
Australopithecus
Australopithecus 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...
, co-existing with already existing members of the Homo genus. This interpretation is based on the observation that the lower jaw, discovered by Friedemann Schrenk, of a 2.5 million year old fossil attributed to H. rudolfensis
Homo rudolfensis
Homo rudolfensis is a fossil human species discovered by Bernard Ngeneo, a member of a team led by anthropologist Richard Leakey and zoologist Meave Leakey in 1972, at Koobi Fora on the east side of Lake Rudolf in Kenya. The scientific name Pithecanthropus rudolfensis was proposed in 1978 by V. P...
is the oldest known fossil ascribed to the Homo genus. This specimen is thus presumed to be older than the Australopithecus sediba fossils. The critics, however continue to ascribe to A. africanus the status of precursor of the Homo genus. Criticism has been raised in a news report on the find in Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
magazine that the authors of the initial description have failed to take the wealth of variation within A. africanus into account, prior to defining the finds as an independent species. Additionally, the basing of the description of the species largely on the skeleton of a juvenile specimen has been subject to criticism, given that there is no certain way of saying to what extent adults would differ from juvenile specimens. This has been a common practice in palaeoanthropology, with even the type specimens of Homo habilis
Homo habilis
Homo habilis is a species of the genus Homo, which lived from approximately at the beginning of the Pleistocene period. The discovery and description of this species is credited to both Mary and Louis Leakey, who found fossils in Tanzania, East Africa, between 1962 and 1964. Homo habilis Homo...
and Australopithecus africanus
Australopithecus africanus
Australopithecus africanus was an early hominid, an australopithecine, who lived between 2–3 million years ago in the Pliocene. In common with the older Australopithecus afarensis, A. africanus was slenderly built, or gracile, and was thought to have been a direct ancestor of modern humans. Fossil...
being juvenile specimens.
See also
- 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...
- List of fossil sites (with link directory)
- List of human evolution fossils
External links
- Australopithecus sediba at the Fossil Wiki
- Pictures of the find at National Geographic
- Skeleton Analysis at Science
- Skulls
- Video presentation explaining the find
- Free Images and resources about "Australopithecus sediba" for Educators and Students
- Guardian Science Notes
