2 de noviembre de 2005

Fósiles de homínidos I: Australopitecos (en inglés)

Prominent Hominid Fossils
Recopilado por Prof. Dr. Julio López Saco

This list includes fossils that are important for either their scientific or historic interest, or because they are often mentioned by creationists. One sometimes reads that all hominid fossils could fit in a coffin, or on a table, or a billiard table. That is a misleading image, as there are now thousands of hominid fossils. They are however mostly fragmentary, often consisting of single bones or isolated teeth. Complete skulls and skeletons are rare.
The list is sorted by species, going from older to more recent species. Within each species, finds are sorted by the order of their discovery. Each species has a type specimen which was used to define it.
Each entry will consist of a specimen number if known (or the site name, if many fossils were found in one place), any nicknames in quotes, and a species name. The species name will be followed by a '?' if suspect. If the fossil was originally placed in a different species, that name will also be given.

The following terminology is used. A skull refers to all the bones of the head. A cranium is a skull minus the lower jaw. A braincase is the cranium minus the face and upper jaw. A skullcap is the top portion of the braincase. Abbreviations: ER East (Lake) Rudolf, Kenya WT West (Lake) Turkana, Kenya KP Kanapoi, Kenya SK Swartkrans, South Africa Sts,Stw Sterkfontein, South Africa TM Transvaal Museum, South Africa OH Olduvai Hominid, Tanzania AL Afar Locality, Ethiopia ARA-VP Aramis Vertebrate Paleontology, Ethiopia BOU-VP Bouri Vertebrate Paleontology, Ethiopia TM Toros-Menalla, Chad

TM 266-01-060-1, "Toumai", Sahelanthropus tchadensisDiscovered by Ahounta Djimdoumalbaye in 2001 in Chad, in the southern Sahara desert. Estimated age is between 6 and 7 million years. This is a mostly complete cranium with a small brain (between 320 and 380 cc). (Brunet et al. 2002, Wood 2002) It 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.

"ARA-VP, Sites 1, 6 & 7", Ardipithecus ramidusDiscovered by a team led by Tim White, Berhane Asfaw and Gen Suwa (1994) in 1992 and 1993 at Aramis in Ethiopia. Estimated age is 4.4 million years. The find consisted of fossils from 17 individuals. Most remains are teeth, but there is also a partial lower jaw of a child, a partial cranium base, and partial arm bone from 2 individuals.ARA-VP-6/1 consists of 10 teeth from a single individual.ARA-VP-7/2 consists of parts of all three bones from the left arm of a single individual, with a mixture of hominid and ape features.

KP 271, "Kanapoi Hominid", Australopithecus anamensisDiscovered by Bryan Patterson in 1965 at Kanapoi in Kenya (Patterson and Howells 1967). This is a lower left humerus which is about 4.0 million years old. (Creationist arguments)

KP 29281, Australopithecus anamensisDiscovered by Peter Nzube in 1994 at Kanapoi in Kenya (Leakey et al. 1995). This is a lower jaw with all its teeth which is about 4.0 million years old.
KP 29285, Australopithecus anamensisDiscovered by Kamoya Kimeu in 1994 at Kanapoi in Kenya. This is a tibia, missing the middle portion of the bone, which is about 4.1 million years old. It is the oldest known evidence for hominid bipedalism.

AL 129-1, Australopithecus afarensisDiscovered by Donald Johanson in 1973 at Hadar in Ethiopia (Johanson and Edey 1981; Johanson and Taieb 1976). Estimated age is about 3.4 million years. This find consisted of portions of both legs, including a complete right knee joint which is almost a miniature of a human knee, but apparently belongs to an adult.

AL 288-1, "Lucy", Australopithecus afarensisDiscovered 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. (Creationist arguments)

AL 333 Site, "The First Family", Australopithecus afarensis?Discovered in 1975 by Donald Johanson's team at Hadar in Ethiopia (Johanson and Edey 1981). Its age is about 3.2 million years. This find consisted of remains of at least 13 individuals of all ages. The size of these specimens varies considerably. Scientists debate whether the specimens belong to one species, two or even three. Johanson believes they belong to a single species in which males were considerably larger than females. Others believe that the larger specimens belong to a primitive species of Homo.

"Laetoli footprints", Australopithecus afarensis?Discovered in 1978 by Paul Abell at Laetoli in Tanzania. Estimated age is 3.7 million years. The trail consists of the fossilized footprints of two or three bipedal hominids. Their size and stride length indicate that they were about 140 cm (4'8") and 120 cm (4'0") tall. Many scientists claim that the footprints are effectively identical to those of modern humans (Tattersall 1993; Feder and Park 1989), while others claim the big toes diverged slightly (like apes) and that the toe lengths are longer than humans but shorter than in apes (Burenhult 1993). The prints are tentatively assigned to A. afarensis, because no other hominid species is known from that time, although some scientists disagree with that classification. (Creationist arguments)

AL 444-2, Australopithecus afarensisDiscovered by Bill Kimbel and Yoel Rak in 1991 at Hadar in Ethiopia (Kimbel et al. 1994). Estimated age is 3 million years. This is a 70% complete skull of a large adult male, easily the most complete afarensis skull known, with a brain size of 550 cc. According to its finders, it strengthens the case that all the First Family fossils were members of the same species, because the differences between AL 444-2 and the smaller skulls in the collection are consistent with other sexually dimorphic hominoids.

KNM-WT 40000, Kenyanthropus platyopsDiscovered by Justus Erus in 1999 at Lomekwi in Kenya (Leakey et al. 2001, Lieberman 2001). Estimated age is about 3.5 million years. This is a mostly complete, but heavily distorted, cranium with a large, flat face and small teeth. The brain size is similar to that of australopithecines. This fossil has considerable similarities with, and is possibly related to, the habiline fossil ER 1470.

"Taung Child", Australopithecus africanusDiscovered by Raymond Dart in 1924 at Taung in South Africa (Dart 1925). The find consisted of a full face, teeth and jaws, and an endocranial cast of the brain. It is between 2 and 3 million years old, but it and most other South African fossils are found in cave deposits that are difficult to date. The teeth of this skull showed it to be from an infant about 5 or 6 years old (it is now believed that australopithecines matured faster than humans, and that the Taung child was about 3). The brain size was 410 cc, and would have been around 440 cc as an adult. The large rounded brain, canine teeth which were small and not apelike, and the position of the foramen magnum(*) convinced Dart that this was a bipedal human ancestor, which he named Australopithecus africanus (African southern ape). Although the discovery became famous, Dart's interpretation was rejected by the scientific community until the mid-1940's, following the discovery of other similar fossils.

(*) Anatomical digression: the foramen magnum is the hole in the skull through which the spinal cord passes. In apes, it is towards the back of the skull, because of their quadrupedal posture. In humans it is at the bottom of the skull because our head is balanced on top of a vertical column. In australopithecines it is also placed forward from the ape position, although not always as far forward as in humans.

TM 1512, Australopithecus africanus (was Plesianthropus transvaalensis)Discovered by Robert Broom in 1936 at Sterkfontein in South Africa (Broom 1936). The second australopithecine fossil found, it consisted of parts of the face, upper jaw and braincase.

Sts 5, "Mrs Ples", Australopithecus africanusDiscovered by Robert Broom in 1947 at Sterkfontein in South Africa. It is a very well preserved cranium of an adult. It has usually been thought to be female, but there has been a recent claim that it is male. It is the best specimen of africanus. It is about 2.5 million years old, with a brain size of about 485 cc. (It has recently been claimed that the fossils Sts 5 and Sts 14 (see next entry) were from the same individual)

Sts 14, Australopithecus africanusDiscovered by Robert Broom and J.T. Robinson in 1947 at Sterkfontein (Broom and Robinson 1947). Estimated age is about 2.5 million years. This find consisted of a nearly complete vertebral column, pelvis, some rib fragments, and part of a femur of a very small adult. The pelvis is more human than apelike, and is strong evidence that africanus was bipedal (Brace et al. 1979), although it may not have had the strong striding gait of modern humans (Burenhult 1993).

BOU-VP-12/130, Australopithecus garhiDiscovered by Yohannes Haile-Selassie in 1997 at Bouri in Ethiopia (Asfaw et al. 1999). This is a partial skull including an upper jaw with teeth which is about 2.5 million years old.

Stw 573, "Little Foot", AustralopithecusDiscovered by Ron Clarke between 1994 and 1997 at Sterkfontein in South Africa. Estimated age is 3.3 million years. This fossil consists, so far, of many bones from the foot, leg, hand and arm, and a complete skull. More bones are thought to be still embedded in rock. (Clarke and Tobias 1995, Clarke 1998, Clarke 1999)

(An increasing number of scientists are placing the following three species, aethiopicus, robustus and boisei, in the genus Paranthropus)
KNM-WT 17000, "The Black Skull", Australopithecus aethiopicusDiscovered by Alan Walker in 1985 near West Turkana in Kenya. Estimated age is 2.5 million years. This find is an intact, almost complete cranium. The brain size is very small for a hominid, about 410 cc, and the skull has a puzzling mixture of primitive and advanced features. (Leakey and Lewin 1992)

TM 1517, Australopithecus robustus (was Paranthropus robustus)Discovered by a schoolboy, Gert Terblanche, in 1938 at Kromdraai in South Africa (Broom 1938). It consisted of skull fragments, including five teeth, and a few skeletal fragments. This was the first specimen of robustus.

SK 48, Australopithecus robustus (was Paranthropus crassidens)Discovered by Mr. Fourie in 1950 at Swartkrans in South Africa (Johanson and Edgar 1996). It is a cranium, probably belonging to an adult female, and 1.5-2.0 million years old. It is the most complete skull of robustus.

DNH 7, "Eurydice", Australopithecus robustusDiscovered by André Keyser in 1994 at the Drimolen cave in South Africa. Estimated age is between 1.5 and 2.0 million years. This is an almost complete skull and lower jaw of a female, one of the most complete hominid skulls ever found, and the first significant fossil of a female robustus. A fossil of a male robustus lower jaw, nicknamed Orpheus (DNH 8), was found a few inches away from it. (Keyser 2000)

OH 5, "Zinjanthropus", "Nutcracker Man", Australopithecus boiseiDiscovered by Mary Leakey in 1959 at Olduvai Gorge in Tanzania (Leakey 1959). Estimated age is 1.8 million years. It is an almost complete cranium, with a brain size is about 530 cc. This was the first specimen of this species. Louis Leakey briefly considered this a human ancestor, but the claim was dropped when Homo habilis was found soon afterwards.

KNM-ER 406, Australopithecus boiseiDiscovered by Richard Leakey in 1969 near Lake Turkana in Kenya. This find was a complete, intact cranium lacking only the teeth (Lewin 1987). Estimated age is about 1.7 million years. The brain size is about 510 cc. (see also ER 3733)

KNM-ER 732, Australopithecus boiseiDiscovered by Richard Leakey in 1970 near Lake Turkana in Kenya. The cranium is similar to that of OH 5, but is smaller and has other differences such as the lack of a sagittal crest. The estimated age is about 1.7 million years. The brain size is about 500 cc. Most experts believe this is a case of sexual dimorphism, with the female being smaller than the male.

KGA10-525, Australopithecus boiseiDiscovered by A. Amzaye in 1993 at Konso in Ethiopia (Suwa et al. 1997). This fossil consists of much of a skull, including a lower jaw. The estimated age is 1.4 million years. The brain size is estimated to be about 545 cc. Although it has many features specific to boisei, it also lies outside the previously known range of variation of that species in many ways, suggesting that boisei (and maybe other hominid species) may have been more variable than is often thought (Delson 1997).