Presentation on theme: "Antiquity of Humanity Basal Hominids Genus Paranthropus."— Presentation transcript:
Antiquity of Humanity Basal Hominids Genus Paranthropus
Theories of Human Origins Cosmologies Religious explanations for our origins, ie. Genesis Mayan Origin Myths Scientific explanations Using Scientific Method to explain origins Evolution Theory of Natural Selection
Sahelanthropus tchadensis This species was named in July 2002 from fossils discovered in Chad in Central Africa (Brunet et al. 2002, Wood 2002). It is the oldest known hominid or near-hominid species, dated at between 6 and 7 million years old. This species is known from a nearly complete cranium nicknamed Toumai, and a number of fragmentary lower jaws and teeth. The skull has a very small brain size of approximately 350 cc. It is not known whether it was bipedal. S. tchadensis has many primitive apelike features, such as the small brainsize, along with others, such as the brow ridges and small canine teeth, which are characteristic of later hominids. This mixture, along with the fact that it comes from around the time when the hominids are thought to have diverged from chi mpanzees, suggests it is close to the common ancestor of humans and chimpanzees.
Ardipithecus ramidus This species was named in September 1994 (White et al. 1994; Wood 1994). It was originally dated at 4.4 million years, but has since been discovered to far back as 5.8 million years. Most remains are skull fragments. Indirect evidence suggests that it was possibly bipedal, and that some individuals were about 122 cm (4'0") tall. The teeth are intermediate between those of earlier apes and A. afarensis, but one baby tooth is very primitive, resembling a chimpanzee tooth more than any other known hominid tooth. Other fossils found with ramidus indicate that it may have been a forest dweller. This may cause revision of current theories about why hominids became bipedal, which often link bipedalism with a move to a savannah environment.
Orrorin tugenensis This species was named in July 2001 from fossils iscovered in western Kenya (Senut et al. 2001). The fossils include fragmentary arm and thigh bones, lower jaws, and teeth and were discovered in deposits that are about 6 million years old. The limb bones are about 1.5 times larger than those of Lucy, and suggest that it was about the size of a female chimpanzee. Its finders have claimed that Orrorin was a human ancestor adapted to both bipedality and tree climbing, and that the australopithecines are an extinct offshoot. Given the fragmentary nature of the remains, other scientists have been skeptical of these claims so far (Aiello and Collard 2001).
Australopithecus anamensis This species was named in August 1995 (Leakey et al. 1995). The material consists of 9 fossils, mostly found in 1994, from Kanapoi in Kenya, and 12 fossils, mostly teeth found in 1988, from Allia Bay in Kenya (Leakey et al. 1995). A. anamensis existed between 4.2 and 3.9 million years ago, and has a mixture of primitive features in the skull, and advanced features in the body. The teeth and jaws are very similar to those of older fossil apes. A partial tibia (the larger of the two lower leg bones) is strong evidence of bipedality, and a lower humerus (the upper arm bone) is extremely humanlike. Note that although the skull and skeletal bones are thought to be from the same species, this is not confirmed.
Scientific Evidence Australopithecines Evolved 5-3 million years ago in Africa The ape that stood up Characteristics Bipedal Small brain size Relatively small body size Between 3 and 4 feet pounds
Bipedality Evidence Female Gorilla Australopithecus africanus Modern Humans
Australopithecus afarensis (ca. 3.5mya)
Lucy Discovered by Donald Johanson and Tom Gray in 1974 at Hadar in Ethiopia (Johanson and Edey 1981; Johanson and Taieb 1976). Its age is about 3.2 million years. Lucy was an adult female of about 25 years. About 40% of her skeleton was found, and her pelvis, femur (the upper leg bone) and tibia show her to have been bipedal. She was about 107 cm (3'6") tall (small for her species) and about 28 kg (62 lbs) in weight.
Kenyanthropus platyops Discovered by Justus Erus, a member of a team led by Meave Leakey, in 1999 at Lomekwi in Kenya (Leakey et al. 2001, Lieberman 2001). Estimated age is between 3.5 and 3.2 million years. This is a mostly complete cranium which came in two pieces: a skullcase which was heavily distorted, and a face which was much better preserved. The fossil has an unusual combination of characteristics, most notably a road flat face and small teeth. The name means "Flat faced man of Kenya".
Australopithecus africanus (ca. 3 mya)
Paranthropus Chronology Diagnostic Features Species Paranthropus boisei Paranthropus robustus Paranthropus aethiopicus
Genus Paranthropus Robust Early Hominids ( mya) Highly specialized features Heavy brows Large teeth, particularly back Large muscle attachment areas Jutting lower jaw (prognathism) Some from East Africa, Some from South Africa
Paranthropus boisei OH 5, "Zinjanthropus", "Nutcracker Man", Paranthropus boisei Discovered by Mary Leakey in 1959 at Olduvai Gorge in Tanzania (Leakey 1959). Estimated age is 1.8 million years.
Paranthropus boisei (KNM-ER 406)
Diagnostic Features The most striking feature of the Paranthropus boisei specimens is the degree of megadontia (large teeth). This species has the absolute largest teeth found in any hominid group, with teeth similar in size to gorillas (who weigh as much as 10 times as much). They are often referred to as hyper- robust due to the massive postcanine megadontia. Features include: The face is more vertically set, more orthognathic (variability in this trait). There is anterior teeth reduction. There is a continued increase in postcanine teeth size. There is a larger cranial capacity ( cc). The sagittal crest is on the mid-brain case, not the posterior.
Paranthropus robustus The species Paranthropus robustus was first discovered and named by the eminent Dr. Robert Broom. Broom made a habit of buying fossil remains from a lime quarry worker, and on a particular visit on June 8, 1938, Broom bought a maxillary fragment containing a first molar.
S. Africa-important sites
P. robustus (TM 1517)
Diagnostic Features The P. robustus remains generally are from three sites: Swartkrans, Dreimulen, and Kromdraai. By far the largest of these sites is Swartkrans. One of the major problems with these South African sites is dating, but generally, robustus remains can be safely placed from myr, and possibly even earlier. The dating of these sites is crucial to understanding the phylogeny of the robust australopithecines, but for now, the dates are somewhat in question. The robustus crania are many, but fragmentary, with a known cranial capacity for just one individual specimen, SK 1585, an endocast with a 530 cc capacity. There is evidence of significant expansion over africanus, with an estimated 15% average increase in brain size over africanus. The sexual dimorphism level of about 20% seems to be basically unchanged. In his analysis of SK 1585, R. Holloway concluded that robustus shows a general trend towards a more modern brain - similar to that of boisei - over that of africanus.
Paranthropus robustus DNH 7, "Eurydice", Paranthropus robustus. Discovered by André Keyser in 1994 at the Drimolen cave in South Africa. Estimated age is between 1.5 and 2.0 million years.
Drimolen Site A new and relatively unknown site in the Rhino and Lion Nature Reserve situated about seven kilometers north of the famous Sterkfontein hominid site. Dr Andre Keyser and Dr Lee Berger announced the discovery and excavation of the most complete skull of an ape-man ever to be scientifically described. The skull is that of a female Paranthropus robustus, also described as a hominid ape-man with very large teeth and a dished face. This specimen has an intact lower jaw and all its teeth preserved. A different specimen comprising just a very large lower jaw and large teeth is that of a male of the same species. This larger jaw was discovered just a few centimeters from the female skull. The newly discovered female skull and the male mandible indicates that the sexes differed more markedly from one another than in modern humans today. This is also the case as in the great apes such as the Gorilla and Chimpanzee. The Drimolen site has to date yielded 79 individual specimens and a large variety of fossil animal species.
P. robustus (SK 48) From Swartkrans, S. Africa
Swartkrans, S. Africa
A Plan of the Kromdraai.
Paranthropus aethiopicus The discovery of KNM-WT (the "Black Skull") occurred in 1986, and is an important part of the australopithecine puzzle. Very little is known about P. aethiopicus, since so few specimens have been attributed to the species, but the features that are known provide important insights into the possible evolutionary history between the "robust" and "gracile" australopithecines. In general, aethiopicus shows a mixture of both primitive and derived features, and dates to a time that makes it important in the its placement into the hominid phylogenetic tree. The first specimen attributed to this species group is a mandible (Omo 18) found in southern Ethiopia, west of the Omo River, in This 2.5 million year old mandible was placed into a new species by its discoverers, who named the species Paranthropus aethiopicus. They believed that the specimen deserved a new species designation because its V-shaped jaw (among other features) distinguished it from the robust australopithecus forms known in the area. Generally, the discovery and designation was ignored by the majority of paleoanthropologists. Not until the Black Skull discovery was there much interest in the specimen, but once KNM-WT was discovered in, interest was renewed in the Omo mandible.
The Black Skull (KNM-WT 17000)
Diagnostic Features The better known aethiopicus specimen is KNM-WT 17000, a nearly complete skull sans the mandible. The specimen is known as the "Black Skull" because mineral uptake during fossilization gave the specimen a blue-black color. The specimen was discovered in a 2.5 myr deposit west of Lake Turkana, and through a wrench in many evolutionary schemes accepted by many researchers. The specimen is similar to a male A. afarensis, but with a very small cranial capacity (410 cc), and an even more powerful nuchal musculature and very developed masticatory apparatus.
Features of the Black Skull The well-developed masticatory (chewing) features are seen by: The large palate with a thick roof. The broken roots of large rooted (and thus probably large crowned) molars and 4th premolar. A flat, flaring face. The combination of a very small brain and enlarged masticatory apparatus leads to the development of a well-developed sagittal crest that meets the nuchal crest to form a compound temporonuchal crest similar to A. afarensis at the rear of the vault. Large anterior tooth sockets. A flattened cranial base. A posterior foramen magnum position. Extreme facial prognathism (jutting lower jaw/face).
The Black Skull (KNM-WT 17000)
What happened to robusts? Specialized teeth for chewing coarse food in grassland/savannah environment. Climate change at around 1 mya could have caused them to go extinct because they were too specialized. Extinct lineage.