Introduction
Genetic and physical similarities demonstrate that modern human species that is, Homo sapiens has a close association to other primate species group called apes. Evidence has shown that humans and great apes of Africa that is, gorillas and chimpanzees including bonobos or pygmy chimpanzees share common ancestor, which lived sometime between 6 million and 8 million years ago. Bonobos are found in Central Africa. It is interesting to note that the two species vary morphologically. Bonobos are characterized by shorter upper limbs, less rugged builds, and longer lower limbs than the chimpanzees and sport a distinguishing coiffure (Lavenda and Schultz 2012, p.101).
The evidence has also shown that earliest humans evolved in the African continent and much of the human evolution happened in this continent. Fossils of the early humans who existed between 2 million and 6 million years ago entirely come from Africa. For that reason, this essay reflects on the evidence for both behavioral and physical traits found in the fossil primates, which are candidates for the above mentioned species ancestral to man. In addition, it compares one of the species from both Australopiths and Homo families.
Primate life was unique due to its resilience, flexibility, and creativity. The ancestral characteristics, which these primates inherited from past non primate ancestors are shown in their postcranial skeletons. These traits include presence of collar bone or clavicle that allowed their flexibility in shoulder joint, presence of 5 digits on feet and hands, and plantigrade locomotion that is, use of palms of their foot and hands. Evidence obtained from the fossils show that there are four evolutionary trends across the primate order. These include reduction in number of teeth, increasing dependence on sense of sight, reduction of face projection and resilience on sense of smell, and lastly increase in brain size (Lavenda and Schultz 2012, p.103). Two extra evolutionary trends, which include greater dependency on the learned behavior and increasing period of dependence of the infant, have been suggested by a number of scholars.
The unique prehensile morphological physical characteristics of the primates include nails instead of claws on some digits, great toes and opposable thumbs, and friction skin on the sores, palms, digits, as well as underside of the prehensile tails. Moreover, these primates had pads at tips of their toes and fingers, which had more nerve endings (Lavenda and Schultz 2012, p.104). According to LeGros Clark, the mentioned evolutionary trends in the above paragraph and these unique traits resulted from an arboreal adaptation or simply adaptation to life on trees.
He further argues that the primate creatures with good grasping activities, superior brain, and acute binocular vision are well suited to arboreal type of habitat. These primates used to feed on insects at night. However, with time, they switched from insect predation to the consumption of plants parts that were edible hence this set the stage for their future evolution resulting to larger brain, visual acuity, grasping hands, as well as behavioral flexibility (Lavenda and Schultz 2012, p.105).
The evolution of these primates is described in different epochs or geological divisions. Paleocene was the initial epoch that lasted from around 65 to 55 mya. Very little is known concerning the primates of this epoch. Nonetheless, fragmentally fossils for Altiatlasius primate, the oldest primate were discovered in the late Paleocene deposits in the North of Africa.
The epoch that lasted from around 55 mya to around 38 mya is called Eocene. The fossils recovered are nearly complete skeletons, jaws and teeth, limb bones, and skulls. The primates during this era were adapids, which had 4 premolars, while the modern lemurs have just 3. In addition, Adapids’ lower canines and incisors were generalized, while the modern lemurs have specialized tooth comb (Lavenda and Schultz 2012, p.105). The other primate was omomyids and resembles the living tarsiers. Most of these primates were much smaller than the adapids. They were adapted for clinging, leaping, and climbing. During the late Eocene, primates that are ancestral to all later apes, monkeys, and humans were discovered. These primates are called anthropoideans.
The epoch that lasted from around 38 to around 23 mya is called Oligocene. During this period, the environments dried up and temperatures cooled. Adapids evolved into the modern lemurs. On the other hand, anthropoideans together with their descendants flourished. Fossil anthropoideans in this period are categorized under parapithecides that seems to be more primitive, and propliopithecids that has numerous fossilized limb bones, skulls, and teeth. Its brain was smaller, its ear wasn’t fully developed, and its eye orbits didn’t face to the front (Lavenda and Schultz 2012, p.106).
The primates during Miocene epoch that lasted from around 23 mya to around 5 mya include proconsul heseloni that seems to have been a tree-dwelling, had no tail, four-footed, and fruit eating. The last epoch is called Pliocene epoch and lasted from around 5.3 to around 1.8 mya. This epoch is in fact a continuation of the “age of mammals.” It was during this period that global climate experienced cyclic variations from dry and cool to wet and warm, and then back to the cool conditions again. The evidence that has been found show that primates during this epoch had upright posture and occasionally walked on their hind limbs hence the appearance of past bipedal human ancestors began during this period (Lavenda and Schultz 2012, p.113)
Evidence has shown that some species under Australopiths and Homo families have comparable traits. Therefore, this essay also compares Australopithecus afarensis to Homo erectus. Specifically, I chose these two species because evidence has shown that Australopithecus afarensis skeleton closely look like that of the modern human beings and Homo erectus had traits closely resembling those of human beings.
Australopithecus afarensis was a walker and tree climber while Homo erectus was a walker and an endurance runner. In addition, Australopithecus afarensis had unbalanced head, narrow shoulders, wide chest, short and wide waist, long femoral neck, long forearm, partial foot arch, and short Achilles tendon. On the other hand, Homo erectus had balanced head, wide shoulders, narrow chest, tall and narrow waist, short femoral neck, short forearm, stabilized foot arch, and long Achilles tendon (Lavenda and Schultz 2012, p.116).
Works cited
Lavenda, Robert H, and Emily A. Schultz. Anthropology: What Does It Mean to Be Human? New York: Oxford University Press, 2012.
"Videos | The Smithsonian Institution's Human Origins Program." Human Evolution by The Smithsonian Institution's Human Origins Program. N.P., n.d. Web. 29 June 2013.
