Psy 201 Week 1 Evolution Research Paper

During the middle to late Eocene and into the Oligocene epoch several other members of the equids, with distinct evolutionary changes, existed including the Orohippus, Epihippus, Mesohippus, and Miohippus. The Orohippus developed from the Hyracotherium and shared many of the same traits. One major change was that the first and second toes disappeared. Another significant change occurred in the teeth. The last premolar changed to become like a grinding molar. Also the crests were more defined showing that the Orohippus’s diet had changed to a tougher plant material. During the middle Eocene a descendant of Orohippus appeared. The Epihippus still resembled a dog-like animal. It had four padded toes on the front leg, and three on the back leg. However, the teeth changed more drastically with two of the premolars changing to grinding molars. Now there were five grinding cheek teeth with low crowns. As

Figure 6 shows a selection of mammalian skulls. The primate skulls are the two on the right and as you can see, they have relatively short snouts. Obviously there is a huge amount of variation in gross skull shape across the mammalian class, but certainly, on average, primate skulls tend to be short. Elaboration of the visual apparatus, with the development of varying degrees of binocular vision. Orbits ringed with bone. Figure 6 also shows the characteristic morphology of the primate orbit. The eyes face forward for binoccular region, the eyes tend to be quite large, and the orbit is either a fully enclosed cup (as in the chimp in figure 6) or a lateral post-orbital bar (as in the aye-aye). In most other mammals (for example the bear and kangaroo), the eye is simply plastered onto the side of the skull and held in place by soft tissue.

Bipedalism was the first evolutionary change to define the hominid lineage. It was a major evolutionary change that changed the way we move. Bipedalism is the condition of using two feet for standing and walking. Before bipedalism emerged we were walking on all fours just as many animals do presently. Bipedal locomotion dates back to 7 million years ago with one of the candidates which is Sahelanthropus tchadensis. The other two candidates for the earliest bipedal hominid are Orrorin tugenesis, and Genus Ardipithecus. This evolutionary change brings about several benefits such as being better adapted to live on savannas, having freed hands, more efficient for travel, and better regulation of body temperature. However, similar to many evolutionary changes, Bipedalism comes with “costs” or disadvantages. These disadvantages include our loss of speed, and more stress on lower body joints including the spine.

.*They are omnivorous, plantigrade and highly social animals *Body is covered with hairs (except palms, soles and face) *Limbs have five digits.

3. Distinguish between members of genus Australopithecus and Paranthropus in terms of time, location, and physical features

In terms of lower limb proportions comparing Australopithecines and Paranthropus, only a few post cranial remains have been discovered. Comparing the post cranial remains of these genera to those of modern day non-human and human apes can give great insight to the locomotion and stature of Paranthropus and Australopithecines.

Velociraptor was a mid-sized dromaeosaurid, with adults measuring up to 2.07 m (6.8 ft) long, 0.5 m (1.6 ft) high at the hip, and weighing up to 15 kg (33 lb).[3] The skull, which grew up to 25 cm (10 in) long, was uniquely up-curved, concave on the upper surface and convex on the lower. The jaws were lined with 26–28 widely spaced teeth on each side, each more strongly serrated on the back edge than the front.[1][4]

But why was bipedalism so critical to human evolution? It is the earliest human feature to have evolved in hominins. Darwin felt that it was to free up the hands for making of tools and weapons. However, the first stone tools don’t appear until approximately 2.5mya, many years after the first evidence of bipedalism in hominids. A more logical explanation may be that bipedalism was selected simply because it is superior to walking quadrupedally. The Efficient Walker theory argues that bipedalism enabled hominids to travel further to locate food and fertile territory which coincided with the disappearance of Miocene forests and emergence of savannas in Africa.

The faces of hominids flatten out because their brow ridge and canine teeth got smaller and cranium got bigger. The Neanderthals have the largest brain case and was 55 cm, Homo sapiens the second largest with 48.5 cm and the flattest face. The A. africanus was the most protruding face with 129° and the brain case was 40 cm.

This racial discussion about cranial size has been going on for centuries, with the White brain and skull being larger than any other race. In recent years, studies have been done, especially by Rushton (1996), who has now changed the racial hierarchy. According to him the Mongoloid is now in the forefront, with Caucasoid next and lastly Negroid. Rushton

The Diprotodon was the largest marsupial known and the last of the extinct herbivorous diprotodontis. About 25 000 years ago they became extinct. They were heavily built, large bellied quadruped whose limbs were sturdy. Its distinctive feet were small and inturned much like wombats. Diprotodon’s have been identified as being close relatives to wombats. It was 4 metres in length and up to 2800 kilograms in weight. The Diprotodon’s upper limb bones were longer then its lower limb bones. They preferred semi-arid plains and consumed vegetation. Fossil evidence has discovered that due to the lower sea levels, and droughts made inland, Australia was inhabitable. Due to this Diprotodon have been found at the centre of Lake Callabonna in northern South Australia trapped in mud as the lakebed dried out. Due to Australia drifting north Woodlands became grasslands as the climate became drier. The Diprotodon is believed to have become extinct due to droughts and the fact Australia was barren and waterless. They are believed to have evolved to smaller sizes to cope with the harsher climate. Therefore, fossil evidence such as the Diprotodon is shown to support the theory of evolution being the cause of the distribution of Australian species after Australia drifted

6. Describe the characteristics of each of the animal skulls that you classified. Be sure to list the Order to which each mammalian skull resides. The chiroptera has large canines, eye orbits and a large head when compared to its body.

Scientifics have been investigating more than twenty of years. In 1974, “Lucy”, a 3.2 million years old skeleton appeared. They thought that it was the discovery of the century. This phenomenon indicated that our ancestors walked upright. Since that moment, researches

In addition, Australopithecus afarensis displayed human-like features due to their ability to walk on two legs. Their femurs were slanted inwards toward their knees that were enlarged and strengthened to accustom their activities. Fossils have indicated that they had arched feet with wide heels along with an aligned big toe similar to other ancestors. Also, their powerful arms and forearms suggest they had the ability to climb trees to protect themselves from predators. Jaws and teeth were intermediate between those of humans and apes as their jaws were relatively long and narrow while their teeth were

There has been much debate concerning the origins of bipedalism. Bipedalism, or the ability to move on two legs (eLucy, 2007) was said to have emerged due to climate change in East Africa, for sexual display purpose, to reduce exposure to sunlight, the need to use weapons and tools and many more (NOVA, 2013). There are numerous arguments associated with bipedalism as no one can be entirely sure as to what constituted to the emergence of this trait, which was first present in hominins Australopithecus Afarensis. Anthropologists claim that there is a missing link in the evolutionary lineage that makes it hard to confirm the real cause of bipedalism emergence. However, there are some models which are widely accepted by scientific world, such