Choose one of the following Essay Example | Topics and Well Written Essays - 750 words

Choose one of the following - Essay Example It has been difficult to determine when this unique trait emerged, but they could have been on their feet before over 3 million-year-old Laetoli footprints were made (Reader and Andrew 413). The prints though did not bear semblance to that of modern, they were indeed those of a bipedal primate. Bipedalism Features They are the impressions of feet that lacked a distinctive human rounded ball, ors welling, at the base of the great toe, that had no well-defined arch, and that retained ever so slightly divergent great toes. Transformation from a quadrupedal knuckle walking to bipedalism involves various anatomical changes; development of longer legs angling of femur inwards, the feet develop an arch, the bigger toe is elongated, the pelvis is lowered, and it broadens. Additionally, the spinal cord of the hominid develops in such a manner that the vertebral bends frontward to sustain bipedalism traits. The Postural Feeding Hypothesis There are several competing hypotheses that have been p ut forward by anthropologists to explain the origin of bipedalism in hominids using non-human primates as referential models for our common ancestors. The postural feeding hypothesis (McGrew et al 282) explains bipedalism from an ecological view and explains the shared feeding behaviours exhibited by the chimpanzee and australopithecines are sufficiently common in other apes to influence anatomy. The hominids fed on relatively short trees and this gave them certain selection characters and instead adopting an upright posture and this lead to bipedalism. The other great apes for example chimpanzees do not have a straight gait and human straight gait is much more efficient than their bipedalism and quadrapedalism Hunt came up with the hypothesis after spending close to seven hundred hours observing chimpanzees in the wilderness in central Tanzania (Lewin 115). From his observation of these great apes in the wild, he found out that their feeding habits bordered on postural and this lea d to bipedalism. The hypothesis suggests that early hominids would reach out for fruits by dangling with the front limbs, and bipedalism was applied by grasping for an overhead branch. He found out that 80% of bipedalism was observed during chimpanzee feeding with arm hanging to stabilize the posture, this become the corner stone of the hypothesis. The australopithecines have shown adaptations of the torso form to arm hanging which infers that the apes adapted to arboreal bipedal fruit collection. A major basis of this hypothesis is the argument that the existence of bipedalism during certain aspects of life in extant apes provides evidence of the selective pressures that led to hominid bipedalism. According to this model, the early origin of bipedalism later evolved gradually into a habitual way of movement and this steadily led to bipedalism by the early man. Heat Hypothesis by Wheeler Peter Wheelers heat hypothesis proposes a thermoregulatory selective adaptation of bipedal homin ids to increased heat loss, increased cooling, condensed heat gain and condensed water necessities (McGrew et al 282). By adopting the bipedal posture, hominids were exposed to cooler air since the speed of wind is faster further away from the ground. Additionally, the

Gigabit Token Ring Research Paper Example | Topics and Well Written Essays - 2000 words

Gigabit Token Ring - Research Paper Example It is possible to make use either of the first two token rings in the same equipment. The drawback to this functionality is that the introduction of a new device to such network brings problems to the entire ring (Carlo, 1998). The token ring was first initiated by IBM in the early 80s in their research facility located in Zurich. In 1985, IBM launched its fist token-ring product as a form of adapter that could be used in their original personal computers. In the following year, in collaboration with Texas Instruments, they jointly developed a chipset to help other companies to develop devices that are compatible with the token ring. The year 1989 saw IBM introduce an improved version of their earlier token ring model which had a speed of 4 Mbit/sec. The improved version had a speed of 16 Mbit/sec and in line with this development; the IEEE 802.5 standard was extended to cover it (Muller, 2003). In the year 1994, the leading suppliers of token ring created the Alliance for Strategic Token-ring Advancement and Leadership (ASTRAL) whose main mission was increase the speed of Token-Ring technology to counter the ever rising popularity of Ethernet technology. The members of this group included: ACE/North Hills, 3Com, Bytex, Bay Networks, Cabletron, Chipcom , Centillion, IBM, Hewlett-Packard, , Intel, Olicom ,Madge, Racore, Proteon, Texas Instruments, SMC, UB Networks., Xircom, and XPoint (Muller, 2003). In 1997, a revised version of 802.5 standards was developed which marked the introduction of Dedicated Token-Ring. It was a form of full duplex token ring that bypassed the usual protocol used by token ring in data transfer. A single station thus had the capability of sending and receiving data streams concurrently. This had the effect of doubling the transfer rate of any token ring such that a 4 Mbit/sec dedicated Token-ring station acquired an overall transfer rate of 8 Mbit/sec. They are mainly Type 1, type 6 and type 3. The first wiring done on token ring