Handwrite your answers (essays, outlines, bullet points, etc.) to each question
ID: 85014 • Letter: H
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Handwrite your answers (essays, outlines, bullet points, etc.) to each question on the sheet provided. Limit attachments to one extra page of drawings, illustrations, etc. per question. Refer to your class lecture notes, study guides, Dan Leiberman's The Story of the Human Bod the Your Inner Fish video series (video available online at HHMI), as well as legitimate internet sources like Wikipedia (watch out for Creationist sites). 1. Describe, illustrate, and explain, and compare what scientists have discovered and/or inferred regarding the distinctive biological, ecological, and behavioral adaptations of Australopithecus afarensis (3.2-3.8 Mya, East Africa)with its predecessor Ardipithecus ramidus (4.4 Mya, East Africa). Compare what is known of the the brain size (cranial capacity), body size, stature, limb proportions, relative size, proportions and orientation of the hips limbs, hands and feet of Australopithecus afarensis with what is known of the brain size (cranial capacity), body size, stature, limb proportions, relative size, proportions and orientation of the hips, limbs, hands and feet of Ardipithecus ramidus. Also, compare the masticatory system and inferred diet of Australopithecus afarensis with the masticatory system and inferred diet found in Ardipithecus ramidus. For chewing systems, compare the relative size and orientation of jaw elements (ascending ramus, corpus, and symphysis, as well as the size and orientation of the jaw muscles for the two species. For the dentition, compare the size and orientation of the incisors, the relative size and homing pattern of canines, relative size and proportions of cheek teeth, thickness of molar amel. Finally, summarize compare what scientists have discovered or inferred from anatomical, paleontological, and stable isotope studies regarding the probable adaptive patterns (habitat, paleodiet, group size, daily activity and foraging patterns, etc.) of Au. afarensis with the probable adaptive patterns (habitat, paleodiet, group size, daily activity and foraging patterns, etc.) of its predecessor, Ardipithecus ramidus.Explanation / Answer
1. Origin
Australopithecus afarensis (Latin: "Southern ape from Afar") is an extinct hominin that lived between 3.9 and 2.9 million years ago. A. afarensis was slender built, like the younger A Australopithecus afarensis is thought to be more closely related to the genus homo (which includes the modern human species homo sapiens), whether as a direct ancestor or a close relative of an unknown ancestor, than any other known primate from the same time. Some researchers include A. afarensis in the genus praeanthroupus
The most famous fossil is the partial skeleton named Lucy (3.2 million years old) found by Donald Johansson and colleagues.
Ardipithecus ramidus, Two fossil species are described in the literature: A. ramidus, which lived about 4.4 million years ago during the early Pliocene and A. kadabba, dated to approximately 5.6 million years ago (late Miocene) Behavioral analysis showed that Ardipithecus could be very similar to chimpanzees, indicating that the early human ancestors were very chimpanzee-like in behavior.
2. Locality
Australopithecus afarensis fossils have only been discovered within eastern Africa. DespiteLaetoli being the type locality for A. afarensis, the most extensive remains assigned to the species are found in Hadar,Afar region of Ethiopia, including the above-mentioned "Lucy" partial skeleton and the "First Family" found at the AL333 locality. Other localities bearing A. afarensis remains include Omo, Maka, Fejej, and Belohdelie in Ethiopia, andKoobi Fora and Lothagam in Kenya.
Ardipithecus ramidus in 1992–1993 a research team headed by Tim White discovered the first A. ramidus fossils—seventeen fragments including skull, mandible, teeth and arm bones—from the, Afar Depression in the Middle Awash river valley of Ethiopia. More fragments were recovered in 1994, amounting to 45% of the total skeleton. This fossil was originally described as a species of Ardipithecus, but White and his colleagues later published a note in the same journal renaming the fossil under a new genus, Ardipithecus. Between 1999 and 2003, a multidisciplinary team led by sileshi semaw discovered bones and teeth of nine A. ramidus individuals at As Duma in the Gona Western Margin of Ethiopia's Afar Region.
3. Anatomy
a) Australopithecus afarensis Compared to the modern and extinct great apes, A. afarensis has reduced canines and molars, although they are still relatively larger than in modern humans. A. afarensis also has a relatively small brain size (about 380–430 cm3) and a prognathic face (i.e. a face with forward-projecting jaws).
b) A. afarensis was almost exclusively bipedal, while others propose that the creatures were partly arboreal. The anatomy of the hands, feet, and shoulder joints in many ways favor the latter interpretation. In particular, the morphology of the scapula appears to be ape-like and very different from modern humans. The curvature of the finger and toe bones (phalanges) approaches that of modern-day apes, and is suggestive of their ability to efficiently grasp branches and climb. Alternatively, the loss of an abductable great toe and therefore the ability to grasp with the foot (a feature of all other primates) suggests A. afarensis was no longer adapted to climbing.
c) A. afarensis skeleton strongly reflect bipedalism, to the extent some researchers have suggested bipedality evolved long before A. afarensis in overall anatomy, the pelvis is far more human-like than ape-like. The iliac blades are short and wide, the sacrum is wide and positioned directly behind the hip joint, and evidence of a strong attachment for the knee is clear. While the pelvis is not wholly human-like (being markedly wide, or flared, with laterally oriented iliac blades), these features point to a structure that can be considered radically remodeled to accommodate a significant degree of bipedalism in the animals' locomotor repertoire.
d) Importantly, the femur also angles in toward the knee from the hip. This trait would have allowed the foot to have fallen closer to the midline of the body, and is a strong indication of habitual bipedal locomotion. The feet also feature adducted big toes, making it difficult if not impossible to grasp branches with the hind limbs. The loss of a grasping hind limb also increases the risk of an infant being dropped or falling, as primates typically hold onto their mothers while the mother goes about her daily business. Without the second set of grasping limbs, the infant cannot maintain as strong a grip, and likely had to be held with help from the mother. The problem of holding the infant would be multiplied if the mother also had to climb trees. Bones of the foot (such as the calcaneus) also indicate bipedality
e) A. afarensis probably was quite an efficient bipedal walker over short distances, and the spacing of the footprints at Laetoli indicates they were walking at 1.0 m/s or above, which matches human small-town walking speeds.Yet, this can be questioned, as finds of Australopithecus foot bones indicate the Laetoli footprints may not have been made by Australopithecus. Many scientists also doubt the suggestion of bipedalism, and argue that even if Australopithecus really did walk on two legs, it did not walk in the same way as humans.
f) The presence of a wrist-locking mechanism, though, might suggest they engaged in knuckle-walking. The shoulder joint is also oriented much more cranially (i.e. towards the skull) than that in modern humans, but similar to that in the present-day apes. Combined with the relatively long arms A. afarensis is thought to have had, this is thought by many to be reflective of a heightened ability to use the arm above the head in climbing behavior. Furthermore, scans of the skulls reveal a canal and bony labyrinth morphology, which is not supportive to proper bipedal locomotion
a) Ardipithecus ramidus On October 1, 2009, paleontologists formally announced the discovery of the relatively complete A. ramidus fossil skeleton first unearthed in 1994. The fossil is the remains of a small-brained 50-kilogram (110 lb) female, nicknamed "Ardi", and includes most of the skull and teeth, as well as the pelvis, hands, and feet it was discovered in Ethiopia's harshAfar desert at a site called Aramis in the Middle Awash regionb) However, because the "Ardi" skeleton is no more than 200,000 years older than the earliest fossils of Australopithecus, and may in fact be younger than they are, some researchers doubt that it can represent a direct ancestor of Australopithecus.
c) Some researchers infer from the form of her pelvis and limbs and the presence of her abductable hallux, that "Ardi" was a Facultative biped: bipedal when moving on the ground, but quadrupedal when moving about in tree branches. A. ramidus had a more primitive walking ability than later hominids, and could not walk or run for long distances. The teeth suggest omnivory, and are more generalized than those of modern apes. This paper argued that erect posture, significant cervical lordosis, reduced facial projection as well as "flexed" cranial base architecture indicate this species possessed greater facility to modulate vocalizations than both chimpanzees and bonobos
4. Behavior
Australopithecus afarensis Reconstruction of the social behavior of extinct fossil species is difficult, but their social structure is likely to be comparable to that of modern apes, given the average difference in body size between males and females. The degree of sexual dimorphism between males and females of A. afarensis is considerably debated. Some propose that males were substantially larger than females. If observations on the relationship between sexual dimorphism and social group structure from modern great apes are applied to A. afarensis, then these creatures most likely lived in small family groups containing a single dominant male and a number of breeding females Other studies have shown there could have been substantial overlap between males and females in size. This, along with the reduction of the canine teeth, has been argued to suggest A. afarensis males and females were monogamous. Males may have engaged in provisioning behavior, and the need for carrying may have led to the evolution of bipedalism.
For a long time, no known stone tools were associated with A. afarensis, and paleoanthropologists commonly thought stone artifacts only dated back to about 2.5 Mya. However, a 2010 study suggests the hominin species ate meat by carving animal carcasses with stone implements. This finding pushes back the earliest known use of stone tools among hominins to about 3.4 Mya.
Ardipithecus ramidus has been used to infer aspects of the social behavior of the species and more ancestral hominids. In particular, it has been used to suggest that the last common ancestor of hominids and African apes was characterized by relatively little aggression between males and between groups. This is markedly different from social patterns in common chimpanzees, among which intermale and intergroup aggression are typically high. Researchers in a 2009 study said that this condition "compromises the living chimpanzee as a behavioral model for the ancestral hominid condition.
A. ramidus existed more recently than the most recent common ancestor of humans and chimpanzees.and thus is not fully representative of that common ancestor. Nevertheless, it is in some ways unlike chimpanzees, suggesting that the common ancestor differs from the modern chimpanzee. After the chimpanzee and human lineages diverged, both underwent substantial evolutionary change. Chimp feet are specialized for grasping trees; A. ramidus feet are better suited for walking. The canine teeth of A. ramidus are smaller, and equal in size between males and females, which suggests reduced male-to-male conflict, increased pair-bonding, and increased parental investment. "Thus, fundamental reproductive and social behavioral changes probably occurred in hominids long before they had enlarged brains and began to use stone tools," the research team concluded.
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