Trends and Analysis of Hominid Evolution – Introduction
Evolution is a simple term for change that occurs with respect to time as species are adjusted and diverge to create numerous descendant species. Evolution has been regarded as the historical event of change, and one of the mechanisms is Natural Selection. In biology, evolution is the release or emergence from an enclosure structure; a change in the features of groups of organisms through a generation. It is essential to take note that natural evolution is referred to the populace and not just to individuals and these changes are passed from one generation to the other.
Charles Darwin’s contribution to ideas about evolution surrounds the theory of evolution which is by natural selection. He emphasizes that this theory is a process of changes in organisms resulting from heritable behavioral or physical traits and also changes that allow these organisms to adapt to their immediate environment for survival and offspring assistances. Charles Darwin’s contribution includes his speculation on how natural selection would cause land mammals to become whales. Furthermore, he described how natural selection depending on an organism’s success could be an attraction to mate – sexual selection. In addition, his observations also led to the discovery of the pattern of evolution. (“Live Science, 2013”)
Fossils are considered the preserved remains of animals or even plants. There are two major types of fossils, these include trace and body fossils. Trace fossils are the remains of an animal’s activities, such as footprints, preserved track ways, and nests. Body fossils are the remains of the body of an animal or plant which are preserved. Fossils can be formed through drying, freezing, and encasement in resin or tar can create fossils. Also, through carbonization or distillation, fossils can be formed. Permineralization or petrification, replacement, molds and casts using internal and external mold can all form fossils. (“Live Science, 2015”)
Human ancestors have been thought to have evolved from Africa in about 200,000 years ago. And since then, humans have continually evolved in Africa and later started spreading to the Middle East around 100,000 years ago. (“Australian Museum, 2015”) The evidences that this process occurred in Africa revolves around the oldest fossils of Homo sapiens that are known are found in Africa. More also, there are living people who demonstrate little genetic diversity and the variety of different DNA are observed to come from a small gene pool, pointing to Africa as an origin. (“Australian Museum, 2015”)
Trends in Hominin Evolution
The hominin evolution with respect to humans was faced with some challenges and this evolved around different sizes of the body parts.
The size of the brain was a gradual development which took a very slow pace. During the earlier years from 6-2 million years ago, the early humans began to walk uprightly and they started to develop simple tools. The size of the brain was only slightly increased. After few more years later – from 2 million-800, 000 years ago, humans were already spreading across the globe, and seeing new environment led to help in an increase in their body, as a result, this led to increase in brain size. From 800,000 – 200,000 years ago, there was a rapid development of the human brain size. (“Human origins, 2015”) Figure 1 shows an evolution of the brain sizes.
Figure 1: Brain Sizes (“Google Pictures”)
The teeth we have today are very smaller to what was the trend this period. The Last Common Ancestor of hominins was similar to the chimpanzees of today. They had large incisors and were un-erect when they first erupted. The canines of the males were more projected than that of the females and this was believed to be small among the hominins. Premolars had small crowns; some with second molars had the largest of the molar teeth. Incisors seemed to be procumbent amongst the earliest hominins, and were relatively small. The reduction is a change from straight rows of teeth in P. Troglodytes to the curved parabolic arc in H. sapiens shown in the figure 2 below.
Figure 2: Evolution of teeth size (“Tumblr Images, 2011”)
Shape of Forehead and Brow Ridges
The shapes of the forehead and brow ridges during this period were different from each other. The change occurred from a very pronounced outwardly sloping forehead, then to a modern chimp-like face, moving into something flatter, and there was a gradual progression, such as the protruding brow which became less pronounced. In the figure below, the second face is a resemblance of the modern human, while the third looks more of a pronounced facial angle and hardly with brow ridge pronouncement. The fourth skull’s brow is more notable and the shorter face it has is similar to a modern female. The fifth skull is more of a sloping angular face, shorter forehead, and larger jaw. Figure 3 shows the analysis of this faces.
Figure 3: Shape of forehead and brow ridges (“Vesselanaw”)
Shape of Pelvis and Spine
The pelvic and spine of the early hominins evolved around Australopithecus afarensis, Au. Aricanus, Ardipithecus ramidus, and Au. Sediba. The upper half of the pelvis is based on the shape of the iliac blades, which is different from that of the apes. The effect of the changes in the shape was linked to a broadening of the sacrum, and the convex curvature of the lumbar spine is supported. The human iliac blades appeared to be shorter than those of apes. The pattern of the Ar. Ramidus pelvis was observed to be ‘mosaic’ in nature. The lower half of the pelvis appeared to be a shape dictated as that of the birth canal. (Gruss & Schmitt, 2015) The figure below shows the shape of the pelvis and spine.
Figure 4: The shape of the pelvis: A. Pan B. Australopithecus C. Human female and D Human male (“Paul Wren, 2006”)
Comparison of Chimpanzee and Hominin Skulls
The cranial capacity is a major difference in that the hominin skulls are of rounded braincase which houses the larger part of the brain is relatively larger than that for the chimpanzee. Also, the chimpanzees display facial prognathism, in that their face protrudes higher than the top of the skull. In addition to this, the skull of the Chimpanzee is not provided with a forehead, and their brow ridges are prominent above the eye sockets, but hominin skulls have obvious forehead and chin. The hominin skulls are of smaller teeth compared to that for Chimpanzees that are larger and sharper. The figure 5 below shows the image of the comparison of these skulls. (Williams, 2015)
Figure 5: Comparison of Chimpanzee and Hominin Skulls. (“McGraw-Hill Online Learning”)
Links between Hominins
A. boisei, H. habilis, Lucy (A. afarensis), A. robustus
A. bosei was between 2.1 and 1.1 million years ago, Homo Habilis was between 2.4 and 1.5 million years ago, Lucy was between 4.2 and 3.9 million years ago, and A. robustus was between 2 and 1.5 million years ago. The face and cheek teeth of the A. bosei were more massive than that of robustus, though similar. Robustus had a massive flat face. Lucy had an apelike face with forehead very low, bony ridge, no chin, and flat nose. The brain size of robustus and A. bosei are much similar; they are both 530 cc. While Lucy varied about 375 to 530 cc and habilis varied about 500 and 800 cc. In height and weight, habilis had been thought to be about 5’0” tall, and about 45 kg in weight, while Lucy’s height varied and it’s between 3’6” and 5’0” and they were considered to be very physically strong weighted, but the females were smaller than the males. While robustus was considered having very massive teeth for grinding, most of them have sagittal crests, and their bones indicated as they were used as digging tools.
Expert researchers have considered robustus and boisei to be variations of the same species. Some do not accept the existence of habilis, and some considered Lucy to still engage in climbing in trees, many others consider it as an evolutionary baggage. (“talkorigins, 2010”)
Analysis of Some Aspects of Hominin Evolution
Evolution of Stone Tools
The Oldowan was the first stone tool common among the Homo erectus fossils. These were sharp flakes developed by striking, or knapping a hard stone against obsidian, quartz, flint or any type of related rock whose flakes can hold edges effectively. One of the usefulness of the stone was to cut through tough hide in order to get the meat away from the bones, as well as break the bones to access the marrow.
The stone tools came about during a drying trend in Africa around 2-3 million years ago. This allowed hominids to be more versatile, and they were also able to extract food from a more prominent range of territories. (Charles, 2009)
This technology was more prevalent amongst the Homo erectus, making a successful way for them to access meat and efficiently aiding their digestion. Additionally, their high interest in meat was another major reason for them devising a means of using this stone tool. (Charles, 2009)
The use of this tool evolved increasingly among this Homo erectus and also led to significant changes in social evolution. There was an increase in the size of the female, since the males had to provide the food needed. And the grandmother hypothesis was involved in the provision of food; where grandmothers had to bring food for their daughters to assist them in raising their offspring. (Charles, 2009)
The technology may have not been in the location associated with the Australopithecine fossils since they are not as differently distributed as the Homo erectus was distributed more widely across Africa and Asia.
Evolution of Agriculture
Hunting and gathering was the way of life in the hominin era. It was based on exploitation of wild animals and even plants. As a result of this, hunters and gathers became relatively mobile, and also had fluid composition and boundaries. Basically, the responsibility of the men was to hunt wild animals and the women gathered nuts, roots, fruits and any related plant-based food, other times, they hunt smaller animals to survive.
The larger number of these hunters and gatherers are nomadic. The difficulty of holding onto subsistence system resources quickly gets exhausted in related region; this is why there are societies to help them survive related challenges. Other challenges faced include low population densities caused from their subsistence system. The method of agricultural evolution became more prevalent amongst the nomadic society they also never had the possibility for the storae of surplus food. There was gender issues associated with this evolution resulting from hierarchical egalitarianism.
Hunting and gathering of food is not in the case of the sedentary society because Nomads are addictive to moving around to search for food. But the sedentary lifestyle finds growing crops and harvesting it easier than moving around in search for food. Agriculture is an addictive process; people who find it better to settle don’t feel good moving around. But during this evolution, there were examples where environmental and climatic degradation actually forced those in the sedentary society to become nomadic. Also, when there is nothing to hunt at some regions, the sedentary society does not bother about hunting and gathering. (“Wiki books”)
Discussion of the Consequences of further Hominin Discoveries
In the discussions given in “The Issue”, it can be seen that the confusion over the discovery of new hominid is demonstrated from the existence of the fossils discovered which serves as the evidence of the human evolution story. From the studies through the content of this task, it was assumed that this evolution was in trend over 2 to 3 million years ago, and this is based on the discoveries of the fossils. There are different Hominin species such as, Sahelanthropus tchadensis, Orrorin tugenensis, Ardipithecus ramidus, Australopithecus anamensis, Australopithecus afarensis, Kenyanthropus platyops, Australopithecus africanus, Australopithecus garhi, Australopithecus sediba, Australopithecus aethiopicus, Australopithecus robustus, Australopithecus boisei, Homo habilis, Homo georgicus, Homo erectus, Homo ergaster, Homo antecessor, Homo sapiens, and many other ones.
The discoveries of these different species would continually cause more confusion on the human evolutionary tree, since the modern human base their conclusions on the existence of the hominin fossils discovery.
Since the discovery of the A. anamensis for Kenya, A. garhi from Ethiopa and A. baherelghazali from chad are traced back to be Australopithecine species, and they are shown to be the genus that are widely spread than expected, the confusion will increase because most of these back up findings are traced back to some biblical accounts. (Feakes, 2013) And these fossils are not demonstrating evolutionary progression that could be considered vivid. It’s just a general accepted phenomenon. (Feakes, 2013)
The ideas relating to the discovery of more hominin fossils leading to more confusion about human origins will be remain consistent. The diverse perspectives of individual scholars who have discovered many fossils and had a strong backup to their ideas will remain bent on the link between Australopiths and Homo. The fact that the fossils are seen at a particular location and they could have died from the same cause, and considering their features, we may agree that there’s a link between Australopithecus and humans.
Since the bone found dates back to around 18,000 years, and older hominin species date back millions of years. We may assume and support the fact that the Hobbit skulls are not a new discovery to demonstrate a link. Since the researchers were able to also find out that the brain size is small, and short in stature, it is another justification. But we can’t really assume this is not a new discovery at the same time, considering the fact that it is highly an unusual skull. More also, since they based the hominid species on LB1 specimen to obtain the features and they discovered the skeleton is a short one, and it was assumed to be a dwarf derived from the specie of the Homo erectus, this claim could be another major point to consider as a good consideration that the specie is more of modern Homo sapiens.
Furthermore, their small brain size with respect to the stone tools, found around these fossils, is another element to prove they are not new discoveries, considering the expertise of the style and advancement of the tools. These confusions will continually linger as much as more findings are carried out on the discoveries.
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