Evolution of Hominins: Tracing the Family Tree - Essay Sample

Introduction

Hominins refer to any family or rather lineages of human beings, from the Homo erectus, Homo habilis, and Australopithecus and neanderthelensis species. Hominins are a general tribe of all organisms that can trace their origin back to the chimpanzees, about seven million years ago (Roberts 56). Hominin evolution, therefore, refers to the evolutionary processes undergone by the Homo sapiens as well as the pan family. Fossil and genetic evidence presented in the family tree states that the hominins first in Africa between 8 and 6 million years ago, while others emerged after that. The current fossil records document the existence of 23 hominins, and while some are closely reacted to the Homo sapiens, others exhibit changes that distinguish them for human beings. The origin of hominins, just as that of Homo sapiens, has been pointed at the southern, central, and eastern parts of Africa, while other sites were later discovered across Europe and Asia. Among the hominins present in fossil records include the Sahelanthropus, Orronin, Ardipithecus, Kenyapithecus, Paranthropus, Australopithecus and the homo tribes and sub-tribes. The hominin shares most of its origin, as well as genetic and phenotypic characteristics with human beings. The few adjustments, differences, and evolutionary traits can, however, be attributed to climate change starting around 10 million years ago, as demonstrated by the savannah hypothesis as well as the pulsed climate variability hypothesis.

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Major Physical and Behavioral Traits of Hominins

From an analysis of hominin species such as Orronin tugenesis and Sahelanthropus tchadensis, there are specific features that define and distinguish from other primates. These species were generally modest in size, and the possessed a brain size that was relatively equal to that of the modern apes. They also exhibited features that allowed them to assume a straight posture when walking. However, these features were not final to most of the other species, since, after some time, the species exhibited evolutionary patterns that made them display powerful jaws as well as long back teeth. These were changes that allowed them to chew on fibrous or tough foods (Roberts 60). Other species developed larger brain sizes that were relative or proportional to their body sizes as well as teeth and jaw sizes were smaller relative to the previous species, or even to their adjacent ones. The gradually yet effectively adopted bipedalism as the primary mode of locomotion, an advancement from their predecessors who exhibited upright postures. The hominin is also believed to have advanced and incorporated the use of stone technology in their activities.

The Savannah Hypothesis

The evolutionary differences evidence in the hominins can be explained through climate change. Paleoanthropologists have created numerous theories and hypotheses as they attempt to understand the role that climate change around sub-Saharan Africa created an avenue, or rather a medium that permeated human (as well as hominin) evolution. Approximately ten million years ago, sub-Saharan Africa received a wave of climatic changes, ranging from the coolness of the temperature to the increase in dryness as caused by the uplift in the East African Rift System (Roberts 65). The long-term impact of these variations was the fluctuation of water levels in east African lakes between high and low, as well as climatic changes.

The climatic changes in the African continent are thus believed to have resulted in evolutionary characteristics in hominins as adaptive ways that could guarantee their survival. Increases brain size and bipedalism, are two of the numerous traits that can be traced to this change. The savannah hypothesis postulates that as a result of the increase in aridity as well as the spread of the savannah climate. This is a hypothesis that is supported by ocean sediments, carbon-isotope data, faunal remains as well as the correlation of timing between climate change and the acquired evolutionary traits in hominins. Bipedalism is considered as the most strategic evolutionary trait, as it allowed for the hominins to easily maneuver the savannah woodlands and grasslands, as it also freed the hands, enabling the hominins to manipulate stone tools as well as carry items. However, while this presents a 'surface' kind of explanation, other theories and hypotheses suggest that the relationship between climate change and evolution was complicated and more profound than explained above. One such hypothesis is the pulsed climate variability hypothesis.

Pulsed Climate Variability Hypothesis

The emergence of new species such as the Australopithecus anamensis and the Ardipithecus were traced in regions that experienced adverse climatic changes, and this suggests that hominins adapted physical and behavioral flexibilities as a way of adapting and coping in the climatic changes and ranges exhibited. This is a stance that can be supported by the variability selection hypothesis created by Rick Potts claiming that the hominin skeleton displayed impressive flexibility that allowed them to survive even in the adverse climatic conditions (Roberts 65). Therefore, as opposed to the gradual climatic variations, the pulsed climatic variation enabled the hominins to develop habit specific variations and traits that allowed them to respond to the rapidly changing climate. The transitional phases between extremely dry and wet seasons suffered shorter time frames, and the pressures that emanated from these seasons could be attributed to the emergence of new species.

The Resultant Traits of Hominins

Bipedalism has been established as one of the resultant features that hominins exhibited after the evolution process. It had numerous advantages, including body thermoregulation, searching for food, traveling for longer distances, raised eyesight for spotting enemies and predators, as well as freeing the hand to enable the use of stone tools (Roberts 69) The Orronin tugenesis species, discovered in 1974 exhibited this trait. The evidence obtained from its femur bone showed that it was thicker, more so towards the shaft. This is the same trait seen in the human femur, as an adaptation for sustaining weights. This was thus evidence for bipedalism. The thick upper limb and the curved fingers showed that the arm was weight-bearing too. The dental composition included a pointed canine, large upper teeth to the front, and low cusped molars, evidence of a diet composed of seeds and fruits. The hominins could thus be said to have lived a terrestrial as well as an arboreal lifestyle. The Ardipithecus kadabba, discovered in 2004, on the other hand, had a thicker molar enamel, pointing to a diet of soft leaves and fruits.

Conclusion

The close resemblance between the hominins and the Homo sapiens points to a similar origin and the events of evolutions. The hominins evolved from their chimpanzee ancestry 7 million years ago. The evolutionary process can be linked to climatic changes in Africa and more so sub-Saharan Africa. Two hypotheses, the savanna hypothesis, and the pulsed climate variability hypothesis have been postulated to explain the origin of the hominins and the changes they underwent to cope with the new climatic changes. The savannah hypothesis point to climate change as a factor that made the hominins change to survive. In contrast, the pulsed climate variability hypothesis credited the extreme climatic changes to the existence of new hominin species.

Work Cited

Roberts Alice. Evolution: The Human Story. 2018. Dorling Kindersley: New York.