The evolution of hominids has been and still is a heated topic of debate. Many scientists debate over which species can be classified as “human”. The root “hominid” refers to members of the family of humans, Hominidae, which consists of all species on our side of the last common ancestor of humans and living apes. The time split between humans and living apes used to be thought of fifteen to twenty millions of years ago, but now the time period has shifted to around five million years ago. Ardipithecus ramidus is said to have live around 4. 4 million years ago.
The original ossils from this species were placed with the Australopithecus genus; however, a new genus was designated to this group by Tim White. Tim White is an anthropologist and co-author of Geological Study of America Bulletin in which this distinction was first stated. This hominid is different from its predecessors because it lacks an incisor tooth, yet posses an ape-like molar structure. Another major defining characteristic of A. ramidus is that the cranial bones that have been discovered reveal this hominid walked on four appendages rather that the more developed species which walked on two.
The next hominid in line is Australopithecus anamensis. This hominid lived for the period of 3. 5-4. 17 million years ago. It was discovered by a Harvard Expedition to the East Lake Turkana in 1995. The classification of A. anamensis was done after extensive research by Meave Leakey and associates. The skeletal structure of this hominid reveals that it was bipedal (walking on two legs) which distinguishes it distinctly from A. ramidus. However, A. anamensis possessed some traits that were similar to hominids before it such as a dental structure that is similar to that of an ape and an ape-like skull.
On the other hand, this hominid has an unique thick tooth enamel and expanded molars. Between 3. 9 and 3. 0 million years ago, Australopithecus afarensis roamed the earth. It was first discovered by Donald Johanson and Tim White in 1978 but the validity of this discovery was questioned for many years. The most popular member of this species would be “Lucy” who was discovered in Hadar, Ethiopia in 1974. The skull of this A. afarensis is like that of a chimpanzee, but it has human-like teeth. It’s canine teeth are larger than modern day apes but more pointed than humans.
Anthropologist Louis Leakey distinguished that the pelvis and legs of A. afarensis show that the hominid walked on two legs and was significantly strong for its small size (ranging from 3’6” to 5’0”). Some anthropologists even believe that the structure of this hominid suggests it was adapted for climbing trees because of its strong structure and curved bones in the fingers and toes. Australopithecus afarensis was one of the first hominids discovered to begin to resemble modern day men. The species Australopithecus africanus was first name in Nature magazine by Raymond Dart in 1925.
He names the species because of his findings of the Taung Child Skull. However, many paleontologists of the time rejected this classification and said that the skull was one of an early gorilla or chimpanzee. Because of the great debate over the species, Dart never went back to Taung for further research. Other excavations have found remains of A. africanus in Sterkfontein, Makapansgat, and Gladysvale. These remains date back anywhere from 2. 9 to 2 million years ago. This species was declared bipedal because of its 5 lumbar vertebrae where most humans have 6 and chimps have 4.
The post canine teeth in A. africanus are much broader and all of the teeth in this species have a great enamel thickness along the tooth wall which set them apart from predeceasing species. Their brain capacity is said to be anywhere from 428 cc to 625 cc, and they are also said to have had a broader nasal cavity than modern day humans. Even though this hominid was not advanced in speech, it shows evidence that hominids were slowly evolving into the human of today. Australopithecus robustus is a hominid species that was first discovered by Dr. Robert Broom in 1938. Dr.
Broom had a habit of collecting fossils from a lime quarry worker. He came across a skull with a molar still in it on June 8, 1938. He began working on a monograph of the australopithecines, and it was published in 1946. This book had such a contribution to the understanding of australopithecines that it was given a U. S. National Academy of Sciences award. The A. robustus remains generally are from three sites: Swartkrans, Dreimulen, and Kromdraai and can safely be dated to 2. 0 to 1. 0 million years ago. The massive face is flat or dished, with no forehead and large brow ridges.
It has relatively small front teeth, but massive grinding teeth in a large lower jaw. Its diet would have been mostly coarse, tough food that needed a lot of chewing. Bones excavated with A. robustus skeletons indicate that they may have been used as digging tools. This is a significant change in behavior and once again shows evolution to the modern day human. It was a great discovery when Zing, the Australopithecus boisei was found by Mary Leakey in Olduvai in 1959. A. boisei was very important in clearing up a controversy that occured in the 1960s over the idea of the “Single Species Hypothesis”.
The single species hypothesis states that each individual environment can only support one species, and that in hominids, “monkey-see monkey-do” holds true. The discovery of boisei of both sexes in the same site brought into doubt the validity of the single species hypothesis. Specimens attributed to A. boisei have been found mostly in Ethiopia, Tanzania, and Kenya in East Africa, and they are said to date back anywhere from 2. 1 to 1. 1 million years ago. It was similar to robustus, but the face and cheek teeth were even more massive, some molars being up to 2 cm across. It also is resent at a time when stone tools become much more common, and may have even made and used some. In the end, however, it seems that A. boisei became too specialized, and died with climatic and/or environmental shifts.
The species designation of Homo rudolfensis is a much debated topic, over both whether it is a separate species, and if it is an australopithecine rather than a member of the genus Homo. This species was discovered by Richard Leakey’s team in 1972, east of Lake Turkana in northern Kenya. H. rudolfensis has an estimated age of 1. 9 million years. The skull that was found was riginally named part of the Homo habilis species, and it became the center of debate. The differences in this skull, when compared to others of the Homo habilis species, are too pronounced, leading to the presumption of a Homo rudolfensis species, contemporary with Homo habilis. In March 2007, a team led by Timothy Bromage, an anthropologist at New York University, reconstructed the fragments of the skull. The new reconstruction found that the cranial shape is much like that of an ape (similar to the Australopithecines before it), and its cranial size is much smaller than originally expected.
Homo rudolfensis may be the first member of the genus Homo on a path to modern humans. The specimen that led to the naming of Homo habilis was discovered in 1960, by the Leakey team in Olduvai Gorge, Tanzania. The specimen was to studied by Louis Leakey and his team which consisted of John Napier and Phillip Tobias. They realized that the material was not the same as the Australopithecines which had come before it because of its teeth, specifically its very large incisors. Also, the large brain size and shape of the hand suggested a closer relation with Homo. In January 1964, the team announced the new species Homo habilis.
The name was suggested by Raymond Dart, and means “handy man,” in reference to this hominids supposed tool making prowess. Habilis existed between 2. 4 and 1. 5 million years ago. This species has a bulge in Broca’s area which is essential for speech and indicates it might have been capable of the beginnings of speech. Homo habilis is a very complicated species to describe. No two researchers attribute all the same specimens as habilis, and few can agree on what traits define habilis, if it is a valid species at all, and even whether or not it belongs in the genus Homo or Australopithecus.
However, the majority of specimens relate more closely with those of the Homo genus rather than Australopithecus, and therefore is classified as Homo habilis. The species Homo erectus was named by Eugene Dubois in 1894, after his 1891 find from Trinil, Java, in Indonesia. One of the most important erectus specimen is the Nariokotome Boy. This specimen was discovered by a team led by R. Leakey and A. Walker at Nariokotome, Kenya, in 1984. This is the most complete early human skeleton ever discovered. Except for modern Homo sapiens, erectus was the most far-ranging hominid to have existed.
Material that has been attributed to erectus has come from South Africa, Indonesia, England, and many other places, too. H. erectus existed between 1. 8 million and 300,000 years ago. Like habilis, the face has protruding jaws with large molars, no chin, thick brow ridges, and a long low skull, with a brain size varying between 750 and 1225 cc. Some specimens indicate the H. erectus may have been more efficient at walking than modern day humans who have had adapt the skeleton in order to birth larger brained infants. There is evidence that erectus probably used fire, and their tone tools are more sophisticated than those of habilis. Homo sapien neanderthalensis or the Neandertal man existed between 230,000 and 30,000 years ago. The material was found in a limestone quarry near the city of Dusseldorf in Neander Valley, Germany. The material recovered consisted of a skull cap, two femora, the three right arm bones, two of the left arm bones, part of the left ilium, and fragments of a scapula and ribs.
These fossils were recovered and set aside to be given to a local teacher, Johann Karl Fuhlrott. Fuhlrott suspected that these bones represented unique pieces of the human past, and eft the description of the material to anatomist Hermann Schaaffhausen. The find was announced jointly in 1857, two years before Darwin’s On the Origin of Species. The Fuhlrott remains were not the first Neanderthal remains discovered, but the first one recognized as belonging to a separate species. The Engis child from Belgium was the first Neanderthal discovered, in 1829, and the second discovered was the Forbes Quarry find from Gibralter in 1848. The species name of neanderthalensis comes from William King, who first named the species in 1863 at a meeting of the British Association, and was prined in the Quarterly Journal f Science in 1864. They are found throughout Europe and the Middle East. Western European Neandertals usually have a more robust form, and they are sometimes called “classic Neandertals”.
The brain case of H. neanderthalensis is longer and lower than that of modern humans, with a marked bulge at the back of the skull. Like erectus, they had a protruding jaw and receding forehead. The chin was usually weak. The midfacial area on this species also protrudes which is not seen in any other species and is said to be n adaption to cold. Neandertals ostly lived in cold climates, and their body proportions are similar to those of modern cold- adapted peoples: short and solid, with short limbs. Their bones are thick and heavy, and show signs of powerful muscle attachments. Neandertals would have been exceptionally strong by modern standards. A large number of tools and weapons have been found, more advanced than those of Homo erectus. Neandertals were formidable hunters, and are the first people known to have buried their dead. Out of all the species discussed thus far, Homo sapien sapiens. There are two opposing iews on the issue of the species’ origin, the multiregional view and the Out of Africa view.
The perspective of multiregionalists is that since the existence of H. erectus, there have been populations of humans living around the old world, and these all contributed to successive generations, eventually leading to modern humans. The perspective of the Out of Africa model adherents is that when there was a migration of H. erectus out of Africa into Asia and Europe, these populations did not contribute a significant amount of genetic material to later populations that led to modern humans.
Modern humans have an average brain size of about 1350 cc. The forehead rises sharply, eyebrow ridges are very small, the chin is prominent, and the skeleton is very fragile. With the appearance of the Cro-Magnon culture, tools became more and more diverse and sophisticated. The species began using a wider variety of raw materials such as bone, found new ways for making clothing, engraving and sculpting. Fine artwork, in the form of decorated tools, beads, clay figurines, and spectacular cave paintings appeared over the next 20,000 years. Even within the last 100,000 years, the long-term trends towards smaller molars nd decreased robustness can be discerned. The tooth size of humans today is significantly smaller than those of Mesolithic or Paleolithic hominids simply because as food processing becomes more common, the larger molars are no longer needed. Modern humans are the most capable thus far in evolution. They are capable f abstract reasoning, language, introspection, and problem solving. This mental capability, combined with an erect body carriage that frees the hands for manipulating objects, has allowed humans to make far greater use of tools than any other living species on Earth.
The hominid family, characterized by bipedal locomotion, appeared between four and five million years ago. This defining event in human evolution was followed by other key events: increased brain size, the initial migration of hominids out of the tropics, and a transition from hunting and gathering to agriculture. While anthropologists agree on this broad sweep of our history, limited data and differing perspectives result in various interpretations and lively debate in the field. However, it is clearly evident that the hominid family has developed and evolved into the complex species we are today.
