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Ecological Conditions Contributing to the Evolution of Early Primates

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Information about the behavior of living primates has increased enormously over the years. During this time the database of early hominids and their habitats has grown rapidly. Scientific studies attempt to use data from actual traces of hominids and their environmental settings to reconstruct their behavior and ecology. In addition, new methods of analysis have allowed for inferences about movement, diet, tool usage and behavioral aspect and ecology of early hominids. Certain aspects of hominid behavior and ecology can be tested directly with evidence from the geological record. The evidence falls into three major categories: fossils, environmental data and archeological records. However, using such evidence to reconstruct hominid adaptations requires analogies established from modern animals’ ad environments., Living primates often contribute to uniformity and analogical bases for reconstruction. In addition, the evolution of early primates is influenced by a multitude of factors.

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Hominid fossils provide data on skeletal morphology and its modification during the life time of an individual, such as growth and changes due to diet and pathology. Fossils are arranged in a chronological order to provide information which will help assess important behavioral and ecological characteristics of early hominids (Mitani, Call, Kappeler, Palombit, & Silk, 2012), for instance, the body size, sexual dimorphism, locomotion, hand functions and diet. Inferences about behavior and body size depend on how well observable anatomical traits correlate with inferred characteristics (Mitani et al., 2012). Illustratively, accurate body weight requires a high correlation between body weight and measurable traits such as the length of the femur. This means that any given value measured from a fossil should correspond to a narrow range of body sizes.

The majority of primates are diurnal and they have variable primate behavioral ecology. In most cases a seasonal signal in these fluctuations is clearly evident. For example, primates are organisms that live within their food sources and therefore, they cannot undertake lengthy seasonal migration to escape from periods with unfavorable conditions (Stanford, Allen, & Anton, 2012). In this case, some species will either increase or decrease their activity during times of scarcity. For example, some organisms will increase their reproduction activity when food is abundantly available. Secondly, primates with long gestational and lactating periods can respond to seasonal conditions by initiating new reproductive cycle. In addition, the early primates from different areas gradually became the modern ones. For instance, the round orbits, large frontal sinuses and thin cranial bones seen in some archaic Homo sapiens from China represent the first appearance of traits that have greater antiquity in Europe (Stanford et al., 2012). The movement of these physical traits has a complex genetic basis that depends upon gene flow among populations. The consistent flow of genes shows the primates’ tendency to exchange them within populations even in the face of cultural barriers. Moreover, without the gene flow, evolution inevitably would not have resulted in the appearance of multiple species that are living today.

Further, modern primates are important for testing correlations between variables in morphology, on the one hand, and anatomical functions on the other hand. However, inferences about early hominids are extrapolations beyond known primate species. This often leads to disagreement about those inferences among scientists (Mitani et al., 2012). For instance, the estimates of body size provide an example of the problems involved. Many scientists consider it inappropriate to apply regression formulas to different populations of Homo sapiens. Therefore, if the application of body weight regression to species is difficult to justify. Furthermore, an estimate of hominid body size must take into account the equivalence in locomotion between early hominids and the reference sample on which the estimate is based (Mitani et al., 2012). A similar problem occurs in functional interpretations of fossils. Modern Homo sapiens is the only biped on which behavioral inferences from early hominid fossils can be based.

Further, other life history traits also contributed to the selection of true primates. These include diet, metabolic rate and activity. For example, among all anthropoid primates taken together, there are two extreme groups. The tarsiers exclusively prey on several arthropods and small vertebrates and avoid plant food. In contrast, the fork-marked lemurs specialize in gums and sap from trees (Mitani et al., 2012). They spend most of their time feeding on them. In addition, species that have mixed diets have different regular or seasonal selection. Putting it in another way, the distribution and availability of different types of food have important implications for selection patterns, competitive regimes and adaptations to life traits. Secondly, the metabolic rate can influence the selection behavior of organisms. Primarily, food provides energy so feeding and dietary behaviors will influence the amount of energy that will be available to support different processes, for example reproduction. Basal metabolic rate (BMR) describes energy expense of an individual. Illustratively, among the primates, most strepsirrhines have a lower BMR than their body mass (Mitani et al., 2012). There are also some species with metabolism that is optimized for saving energy and water. Some species even hibernate and remain inactive during the dry season.

The fossil records provide evidence of a much greater diversity of new world monkeys from both earlier and later times in disparate geographic regions. It, therefore, gives a simple view that their evolution has been static for the past 20million years. Monkeys evolved during the early Oligocene and they were the first species of Anthropoidea (Flatt & Heyland, 2011). Apidium and Aegyptopithecus are most identified genera. Most of the knowledge about the anthropoid evolution comes from the Eocene/ Oligocene deposits in Egypt. Until recently, the fossil primates from the Fayum could be allocated into one of two families of early anthropoids: Aegyptopithecus and Propliopithecus (Flatt & Heyland, 2011). There are genetic and environmental factors that influence the lifespan of the primates. However, the extent to which mutations can influence the lifespan and affect fitness in natural environments is unknown. Moreover, it is not known whether in natural populations the species had loci containing genetic variations which could lead to variations in phenotypes (Flatt & Heyland, 2011).

The same case can be applied to primates; the environment in which the genome effectively evolved has changed. Many aspects of modern environment have changed including diet, lifestyles and exposure to chemicals that mismatch the evolution state of the bodies (Flatt & Heyland, 2011). The genes that were originally selected for survival in adverse conditions are now expressed under completely new environmental conditions. Such mismatch is the underlying explanation for prevalent diseases such as diabetes and obesity. Surprisingly, the genes that increase the ability to store energy in times of abundance and use these stores in shortages contributed to a survival advantage (Flatt & Heyland, 2011). However, with modern eating habits where food is available constantly, these genes are thought to underlie the increased prevalence of diseases.

The evolution of the nasal structure seen in Proconsul and other early Miocene forms of distinct anatomical configurations in mid and late Miocene hominids is an example of this process and its outcomes (Mitani et al., 2012). The fundamental division is between gibbons and large-bodied apes such as the Pongo, the African chimpanzee, Pan and gorilla. Pongo and Pan have common dental adaptations but different cranial features, whilst the gorillas’ cranial is similar to that of the Pan despite contrasting dietary niche. These differences in patterns show there is no one-to-one correspondence between morphology and adaptation. All extant apes and early hominoids are essentially from tropical ecosystems, such as savannah and woodland forests (Mitani et al., 2012). None of them was present in higher latitudes, thus reflecting a rather narrow environmental range compared with earlier ape habitat. In contrast, Miocene hominoids are components of remarkable distinct and diverse faunas. The community relationship within earlier faunas differs from contemporary ecological webs. Moreover, the habitats of earlier hominids in their ecological communities are unlikely to correspond closely to those of modern apes. Miocene flora also changed as climatic conditions altered.

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For example, although it is difficult to trace relative changes in brain mass, it appears to increase with changes in diet and life history (Mitani et al., 2012). It is argued that modern hominid-sized brain brains appeared in the late middle Miocene and did not change significantly until the appearance of the Homo. The timing and duration of a life history event can be reconstructed from fossil records. The M1 emergence shows that a hominoid-like pattern of growth was present in the early Miocene. In addition, reviewed evidence of diet and foraging patterns of fossil apes show the increase in dietary challenges to cognition through time (Mitani et al., 2012). The hominoids moved from a year generalized with few expectations to greater seasonal reliance on other foods.

In conclusion, the evolution of early primates is influenced by a multitude of factors. Environmental conditions can have a considerable effect on lifespan and influence the expression of genetic information. The evidence for ecological conditions that contributed to the selection of primates can be traced from geological records. Hominid fossils provide traces of morphological and behavioral adaptations of primates. Adaptations to selected environments were further influenced by dietary habits, food availability and activity of different species. Moreover, modern environments have influenced the expression of genetic information. Different genes are not working as they were originally supposed to in natural environments and habitants.

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