Definition of Primary versus Secondary Sources:
Primary Source - Primary sources are original materials. They are from the time period involved and have not been filtered through interpretation or evaluation. Primary sources are original materials on which other research is based. They are usually the first formal appearance of results in physical, print or electronic format. They present original thinking, report a discovery, or share new information.
Examples include: Artifacts (e.g. coins, plant specimens, fossils, furniture, tools, clothing, all from the time under study); Audio recordings (e.g. radio programs) Diaries; Internet communications on email, listservs; Interviews (e.g., oral histories, telephone, e-mail); Journal articles published in peer-reviewed publications; Letters; Newspaper articles written at the time; Original Documents (i.e. birth certificate, will, marriage license, trial transcript); Patents; Photographs Proceedings of Meetings, conferences and symposia; Records of organizations, government agencies (e.g. annual report, treaty, constitution, government document); Speeches; Survey Research (e.g., market surveys, public opinion polls); Video recordings (e.g. television programs); Works of art, architecture, literature, and music (e.g., paintings, sculptures, musical scores, buildings, novels, poems). Web site.
Secondary Source - Secondary sources are less easily defined than primary sources. They are interpretations and evaluations of primary sources. Secondary sources are not evidence, but rather commentary on and discussion of evidence. However, what some define as a secondary source, others define as a tertiary source. Context is everything.
Examples include: Bibliographies (also considered tertiary); Biographical works; Commentaries, criticisms; Dictionaries, Encyclopedias (also considered tertiary); Histories; Journal articles (depending on the disciple can be primary); Magazine and newspaper articles (this distinction varies by discipline); Monographs, other than fiction and autobiography; Textbooks (also considered tertiary); Web site (also considered primary).
(Source: University of Maryland)
Step 1: Reading on Ardipithecus Ramidus - Read the 2009 National Geographic article, "Oldest Skeleton of Human Ancestor Found" [Word Version] identifying and citing the key central ideas and information within the text.
Step 2: Researching Fossil Evidence (Primary & Secondary Sources Explained) - Look at the pictures of various fossil evidence found on Ardipithecus Ramidus. Read the corresponding descripions from National Geographic. Take note that the actual fossils are primary sources, but the descriptions contain interpretations and are, therefore, secondary sources. The fossils tell us much, but archeologists and scientists infer or interpret these fossils to make conclusions about how Ardipithecus may have lived. The words or language that indicates that a scientist or archeologist is interpreting a primary source (fossil) is emboldened in the text below to show you how to distinguish between primary and secondary information. For example, when the author below writes that "evidence suggests..." he/she/they are making interpretations or coming up with conclusions/opinions from or about the primary source(s). Be careful when reading. [Printable Version]
Fossil Locations (Background): Western Afar, Ethiopia - Where Ardi was found
The locality where Ardipithecus ramidus was recovered lies in the Awash valley of Ethiopia. Soils, fossils, phytoliths and stable isotope evidence all suggest that when Ardipithecus ramidus was alive the local habitat in Ethiopia was a woodland, rather than the savanna (grassland) usually associated with Australopithecus. Hackberry, fig and palm trees are recorded, as are fish, terrestrial tortoises, crocodiles and 29 species of birds (barn owl, falcons, pigeons, spoonbills, geese, bustards, quail, eagles); small mammals (rodents, rabbits, mice, bats, mice, porcupines, hedgehogs, mongoose, shrews); and hippos and monkeys.
All of these animal species lead researchers to believe that Ardipithecus lived and died in a wooded area that included closed and grassy woodlands and patches of true forests. The food available in the vicinity of A. ramidus, as well as examination of tooth enamel and tooth shape, lead researchers to suggest that Ardi had a diverse vegetarian diet, made up of fruit and other woodland-based foods like nuts and leaves.
Fossil/Primary Source: Ardipithecus Ramidus Skull Front View
"Ardi" stood about 47 inches (120 centimeters) tall and weighed about 110 pounds (50 kilograms). The face of "Ardi" did not project as much as those of modern apes, but was not as flat and massive as the later australopithecines. Researchers who studied the species suggest this difference is related to the small size of the species' incisor teeth compared to those of chimps. Based on the relatively small size of its brow ridge and canine teeth, scientists suggest this fossil is of a female.
While A. ramidus was quite apelike in appearance, researchers who studied the fossil skeleton suggest the species lacked the adaptations of living apes for climbing vertically, hanging from branches, and walking on its knuckles. Instead, it was a "careful climber" in the trees, and supported its weight on the palms of its hands while using its divergent big toe for grasping.
The feet of the new ancestor were more like those of Old World monkeys, which have feet that are more rigid and provide a better lever for walking. The lower part of A. ramidus's pelvis, however, kept an apelike condition, probably to help strong leg muscles still useful for climbing.
Fossil/Primary Source: Ardipithecus Ramidus Skull - Multiple Views
ARA-VP-6/500, nicknamed Ardi, is a partial hominid skeleton of Ardipithecus ramidus, recovered from the Lower Aramis, Ethiopia member of the Central Awash Complex in Ethiopia's Rift Valley. Large fragments of the creature's cranium (skull), mandible (jaw), both hands, both feet, one leg (femur and tibia), and both arms were recovered, including ~100 bones. The skeleton is of a tall, massive female, with a bipedal standing height of 120 centimeters and a weight of about 50 kilograms. She had a small face and reduced teeth, and scholars believe she is a common ancestor of both humans and African apes.
Ardi's skull was unusually complete, if badly crushed, but it allowed researchers a close look. The skull has a small cranial capacity (place for a brain), both in general and in comparison to her body size. She had a projecting muzzle, but it didn't project quite as far forward as modern African apes do. In this facial area she significantly differed from both modern apes and her theoretical ancestor, Australopithecus. Ardi's face does appear to be close to another ancient hominid called Sahleanthropus, leading some researchers to suggest that the two were actually one species; but further data needs to be collected first.
Fossil/Primary Source: Ardipithecus Ramidus - Teeth
To date, more than 145 teeth of Ardipithecus ramidus have been recovered from the Middle Awash region, including several strips of lower (mandibular) and upper (maxillary) jaws. These teeth have thinner enamel layers than Australopithecus but not as thin as chimpanzee teeth. The dental morphology and wear pattern of Ardi, the partial female skeleton ARA-VP-6/500, offered a unique opportunity to study the teeth in the jaw of the animal; researchers concluded that Ardi was a partially terrestrial (walked on land) and partially tree-living animal that dined a wide variety of plants, primarily from the woodland habitats and small patches of forest in her region.
The surprise with A. ramidus is that her upper canines are not the long, sharp pointy ones that are seen in male chimpanzees and related species, but rather blunt stubby teeth more like modern humans.
Fossil/Primary Source: Ardipithecus Ramidus - Hands
The hands and wrists bones of Ardi, the substantially complete skeleton of a 4.4 million year-old Ardipithecus ramidus discovered in Ethiopia, are virtually intact, and they show curiously non-ape like aspects. She had extremely long fingers and an opposable thumb, with a comparatively narrow palm. The joints of her hands were flexible, allowing her to support her weight on her palms. Ardi had a generalized, dexterous, grasping hand unlike any modern apes, suggesting that our ancient ancestor never walked on her knuckles or climbed trees vertically or suspended herself from tree limbs.
Fossil/Primary Source: Ardipithecus Ramidus - Pelvis
Ardi's femur and pelvis offered a close look at the stride of Ardipithecus ramidus, and it again came as a surprise. Although Ardi worked with a more primitive bipedal gait than her supposed ancestor Australopithicus, when on the ground she stood upright and was bipedal, at least when standing on the ground, in contrast to African apes still in existence. Ardi could still move about in trees, as evidenced by powerful hindlimb muscles, but by 4.4 million years ago, our ancestors were already well-established walkers.
Fossil/Primary Source: Ardipithecus Ramidus - Feet
Several foot bones of Ardipithecus ramidus have been discovered among the 110+ individuals discovered in the Awash valley. Researchers suggest that Ardi would have successfully climbed trees and walked upright, with a foot adapted to both tree environments and walking on the ground. The feet were rigid enough to support bipedalism, but had an opposable toe, that allowed the feet to grasp tree limbs. This configuration is yet another piece of information suggesting that hominids developed different evolutionary traits unlike African apes by 4.4 million years ago; and perhaps that characteristics of African apes developed after we split apart from them.
Secondary Source: Ardipithecus Ramidus - Artist Rendition
Up until today, the best known ancient ancestor of ours has been the Australopithecus afarensis known as Lucy, more than a million years younger than Ardipithecus. A. ramidus was different from Lucy, different from modern apes and different from modern humans, in that he moved differently, had a mobile lower back and a robust and flexible hand structure.
Researchers have believed since the discovery of Lucy that both African apes in existence today and hominids evolved from a transitional ape-like ancestor, but the investigation of Ardipithecus ramidus suggests that the anatomy of living African apes—including knuckle walking, vertical climbing and suspension (hanging from trees) behaviors—evolved after the hominid line broke away from them. In other words, the anatomy and behavior of hominids has deeper roots than scientists believed even as short a time ago as 15 years.
According to researcher Owen Lovejoy, the discovery of such a fully bipedal, upright hominid with a small cranium and upright pelvis, who lived in a wooded area and walked on the ground and in trees suggests a range of behaviors. These behaviors—food-carrying, mating with one of the opposite sex, and reduced advertisement of ovulation—all would have intensified male parental investment. That adaptation, says Lovejoy, seems to have marked an evolutionary pattern which created the differences between apes and humans.
Step 3: Analyze the Relationship Between What the Primary Source(s) Tells Us and the Secondary Source Tells Us - Imagine you are a reporter for National Geographic and are covering the fossil discovery and expert analysis for Ardipithecus Ramidus in Ethiopia. Write a summary of what fossil evidence has been found and what the experts believe it suggests...BUT, pretend they NEVER found the PELVIS fossil! How might this change the story behind Ardi? - Complete the Analyzing the Relationship Between Primary and Secondary Sources Handout [Word Version]
Supplemental Video: Discovering Ardi (Summary)
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