Hominin evolution
Introduction
The scientists who study the human evolution have come up with several theories as to how evolution could have taken place. In their study, they contend that ecological conditions and the behavioral patterns played a significant role in the evolution of the genus homo. This paper will analyze the ecological conditions and the behavioral patterns that motivated the evolution of the Homo erectus, archaic Homo sapiens, Neanderthals, and the early Homo sapiens. The study will discuss concerning the Pleistocene ecological conditions that that resulted in the selection of the genus homo. A special analysis will be carried out to determine the population pressures and the ecological factors that that resulted to the dispersal of the genus Homo, evidence of interbreeding for the last I million years will be given.
Pleistocene ecological conditions
The Pleistocene was characterized by an extreme world cooling and recurrent glaciations. In the coldest periods, the world, temperatures dropped by 5degrees and ice sheets spread out from the pole and the high mountains around the world (Bramble & Lieberman, 2005). In between the glaciations, there were warmer periods that were observed with temperatures that are quite similar to the present time (Kimbel, 2009). The continents that lie in the North were more affected by the changes that took place during this time; the South remained in a tropical and subtropical position. The coldest regions of the world changed to become deserts (Leigh, 2014). The evolution of human was much affected by the climatic changes that were taking place during this time. The changes brought new and powerful natural selection pressures. Humanity was able to survive the times by becoming more and more intelligent and adaptable (Rightmire, 1981).
The ancient hominid remains, have been found in different areas around the world, some have been found in the wooded habitats and others in diverse types of vegetation that are located in small geographical areas (Bramble & Lieberman, 2005). The reconstructions of the ancient habitats of Aprdipethecus ramidus have revealed two different sites in Ethiopia, suggesting that the species occupied the grasslands and the woody areas (Bramble & Lieberman, 2005). The increased aridity in the world causes a shift in the Habitat and the vegetation as a possible consequence of this change, Homo erectus developed a set of psychological features that link him close to the modern man, his lower limb length and a nasal morphology (Bramble & Lieberman, 2005). The need to walk for very long distances in search of food and water may have been the contributing factors that led to the formation of the long limbs and other adaptations in Homo erectus. The Homo erectus also revealed an adaptation for dry, arid habitats through its nasal morphology (Rightmire, 1981).
The evolution of the Homo erectus occurred during the Pleistocene, many fossils of this species have been discovered in areas around China, Europe, and Throughout Africa. The late Pleistocene that was discovered in Dusseldorf represents the Neanderthal, a species that is closest to the human species (Leigh, 2014). It is after the discovery of the Homo erectus that the Acheulian tools were found, they were more complex tools compared to those that were used by early hominids (Bramble & Lieberman, 2005). The habitat of the Homo erectus was varied and this enabled the dispersal across the old world.
It is likely that the Neanderthals evolved in Europe, this was partially in response to the cold climate, and they then migrated to the West of Asia, where they could have encountered the Homo sapiens in the Levant (Bramble & Lieberman, 2005). No skeletal evidence has been found to determine if they ever reached Africa. Some of the features that argue for the adaptation to the seasonal frigid biomes include the stocky torsos, shorter limbs and the distinctive facial structures (Bramble & Lieberman, 2005). The middle of the species face protrudes, the teeth are set forward, and the enlarged cheekbones sweep backward. All the nasal passage is voluminous (Rightmire, 1981). In case the Neanderthals wore the animal fur and other materials to help them insulate their bodies, the nasal chambers would assist them to cool the blood and prevent a case where the brain would be overheated. The early Homo sapiens replaced the indigenous hominid species that were in Eurasia, as the sea levels began to drop during the glacial periods, the adventurous individuals travelled to Australia by the use of watercraft (Bramble & Lieberman, 2005).
Population pressures and ecological factors that contributed to the dispersal of the genus Homo
It has been previously stressed that during the early Pleistocene, several species disperse out of Africa; this has mainly been caused by the influence in ecology and the population pressures. The adaptive response of the hominid to such changes was to create and socialize the extra somatic behavior, this means that they came up with new technology (Bramble & Lieberman, 2005). The process resulted in the behavioral changes among the hominid groups as a result of the increase in the operational intelligence (Bramble & Lieberman, 2005). The hominid increased the ability to get energy from the environment through the diversification of the strategies for life and methods to acquire food. In turn, this development resulted in the demographic growth within the genus Homo; this resulted in competition and more pressure on the environment that contributed to the movement of the species to other regions (Bramble & Lieberman, 2005).
Evidence that has been acquired from Damais in Georgia plus the remains of Homo Erectus are used to explain the first wave of the dispersal, the dispersal is as a result of the social reorganization of the social behavior among the earlier homo ancestors (Kimbel, 2009). The later dispersal that took place in Eurasia beyond the near East corresponds to moments of important social reorganization and demographic development; this is coherent with the phases of socialization and demographic growth over Africa and the near East (Bramble & Lieberman, 2005).
Evidence for interbreeding over the past 1 million years, culminating in our modern human genome
Many theories have indicated that the Homo sapiens and the Neanderthals lived together side by side and they often interacted with one another. They interbred and this resulted to the modern man (Leigh, 2014). The interbreeding could have assisted our ancestors adopt in regions that they had not lived before. The interbreeding of the Homo sapiens and the Neanderthals resulted to the growth of people who had a thick skin (Bramble & Lieberman, 2005).
Early symbolic behavior, cultural adaptations, and/or communal activities
The archeological evidence has revealed that the most recent hominid were omnivorous, the amount of meat in the food that they ate and whether they acquired it through hunting or scavenging has been poorly documented by researchers (Bramble & Lieberman, 2005). The stone tools and the cut marks in many archeological sites reveal a long history of meat eating in the tribe of the Hominine, however, this practice could have been there even before the stone tools were invented (Leigh, 2014). Just like the chimpanzees, the Homini may have killed their prey by using their hands and jaws instead of using tools. The extent to which this hunting practice could be determined to be communal and coordinated through the symbolic communication is yet to be determined (Bramble & Lieberman, 2005).
There is no valid way that can be used to tell the group size of the earliest humans, this is because of the little evidence in terms of the movement patterns (Bramble & Lieberman, 2005). However, during the late Paleolithic, the archeological traces of the human made shelters were observed; they became common in the regions that had a notable season inclement (Bramble & Lieberman, 2005). Occurrences of spirituality are elusive as it is hard to find morphology or archeological evidence that is related to these elements. However, it has been proven that Neanderthals used to bury their dead (Bramble & Lieberman, 2005).
Explanation for modern humans (Homo sapiens sapiens) being the only species of the genus Homo alive today
The history of the human is described through the genome, the human looks the way they are because of the genetic changes that have affected their ancestors (Bramble & Lieberman, 2005). Mutation is a natural process that brings change to the DNA, it is very common (Leigh, 2014). The entire human family falls under one single species that has the same genes. Through mutations, there was creation of different versions of the same genes that are known as alleles. The alleles account for the difference that we see in people, this includes the tone of the hair, the skin color, the shape, height and their ability to cope with some various situations for example, disease. Genetic variation has helped the human population to change over time, through the genetic variation, human are able to pass the characteristics to the next generation. Variations preventing survival and reproductions are removed from other populations. The scientific concept of selection brought new, evident in the human population today.
The advancement in the tools, technology leads to the better cognitive abilities in human. Developed cognitive functions enabled the hominids to create social organizations. The social organizations motivated the birth of particular cultural practices like trade (Bramble & Lieberman, 2005). Advanced technology enhanced the hominids lifestyle, they were able to hunt by using spears, and other tools, availability of food resulted in growth in demography a significant factor in the survival of the hominids (Leigh, 2014).
Conclusion
In conclusion, ecological and behavioral patterns motivated evolution activities. The transitions from the Pleistocene indicates that the changes that occurred in climate made the hominids develop certain characteristics to adapt to the demanding atmosphere, this included but not listed in the development of better limbs for walking long distances to look for food and shelter, jaws and tools used for various activities like hunting. The movement of the Hominid from African to other parts of the world was largely caused by demographic growth and the ecological changes that were taking place during that time. Neanderthal and Homo sapiens interbred to come up with the modern Homo.
Reference
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Kimbel, W. H. (2009). The Origin Of Homo. Springer , 31-37.
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Rightmire, P. G. (1981). Patterns in the Evolution of Homo Erectus. Paleobiolog, 241-246.
Zimmer, C., & Emlen, D. J. (2013). Evolution: Making sense of Life. New York: Routledge.