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Models Regarding the Emergence of Bipedalism

There are over ten hypotheses as to how and why bipedalism evolved in humans and when. Bipedalism evolved well before the large human brain or the development of stone tools. Bipedal specializations are found in australopithecus fossils from 4.2-3.9 million years ago. The different hypotheses are not necessarily mutually exclusive and a number of selective forces may have acted together to lead to human bipedalism. Possible reasons for the evolution of human bipedalism include freeing the hands for tool use and carrying, sexual dimorphism in food gathering, changes in climate and habitat (from jungle to savanna) and to reduce the amount of skin exposed to the tropical sun. Another explanation is the mixture of savanna and scattered forests forced the first humans to travel between clusters of trees and bipedalism offered greater efficiency for long-distance travel between these clusters than knuckle-walking quadrupedism.
Step One: Tool Use
Evidence for use of stone tools first came from Olduvai Gorge in Tanzania. These tools were found in the lowest levels dating to nearly 2.0 million years ago. In southern Ethiopia, stone tools dating to as early as 2.3 to 2.4 million years ago have been discovered. Someone or something has modified the. There are different kinds of tools as well. The overall evidence suggests that between 2.3 and 2.5 million years ago hominids began to use stone materials as tools. The first stone tools were probably made for two purposes: cutting something and pounding on something. Obviously you can cut and pound plant materials or use stone tools to dig for roots and such things. However, it is far more likely that some hominids began to cut hides and meat and chop on bones to extract protein rich marrow. Of all of the tools made, the most important was probably the sharp flake that provided the edge by which one could cut even the toughest hides. It is probably unfortunate that the first stone tool tradition, the Oldowan Tool Tradition, is defined as a “core-chopper tradition”. Cores are the means to detach flakes and it is these that were so vital to early hominid stone tool users.
Step Two: Bigger Brains
About one million years ago, hominoid mammals started to exhibit rational thought, a mental process that represented an important advance over simple natural and emotional reactions. Rational thought or is the conscious ability to add sensory input with memory by the use of logical thought processes. Also, morality emerged, which was reliant on the emergence of intelligence.Modern humans (homo sapiens) appeared approximately 160,000 years ago. And until about 12,000 years ago, when agriculture developed, they lived in small groups as hunters and gatherers. They had large brains that had evolved like everything else because it gave the individual and the group, as well as the individual within the group, a competitive advantage: Language allowed better communication within the group and higher forms of thinking. The passing on of knowledge from generation to generation, culture, evolved simultaneously or sometime later. The transfer of more complex information, ideas and concepts from one individual to another, or to a group, was probably the single most advantageous evolutionary adaptation for species preservation. The advantage of learning from passed on knowledge is it allowed foresight and planning. This gave them the ability to adapt to various environments and move to the top of the food chain. With these developments, social survival skills within the group became more important, for the socially fittest produced more offspring. Hence, the larger-brain-yielding genes were more successfully passed on.
Step Three: Thermoregulatory Advantages
Wheeler’s thermoregulatory model proposes, “as the selective pressure, bipedalism conferring reduction in heat gain and facilitation of heat dissipation. Bipedalism raises the mean body surface higher above the ground, where more favorable wind speeds and temperatures prevail. Greater wind flow translates to higher convective heat loss. Bipedalism reduces evaporative cooling requirements and conserves body water. Vertical orientation also minimizes direct solar exposure during the time of day when the solar radiation is most intense.” This basically says that by being upright, hominids were exposed less to harmful elements yet gained the benefits of others.
Step Four: Travel For Food
More specific causes for the adoption of upright posture could be things such as carrying, display or warning, new feeding adaptations, tools, or a combination of these. A conservative view is that the hominid ancestor maintained the typical hominoid foraging regime in a Miocene habitat in which food was becoming more and more widely dispersed and required greater terrestrial travel to harvest. Bipedalism could easily have been the mode of terrestrial travel for this tree adapted hominoid, as it is in all of the modern species of lesser apes, since modern hominoids are equally efficient as bipeds or as quadrupeds at normal speeds. Given the added advantage of free forelimbs, bipedalism for a small hominoid seems likely. The adoption of bipedalism by a Miocene hominoid need not be taken as such an unlikely occurrence, especially given the fact that all lesser apes today are habitual bipeds and bipedalism can easily be adopted by modern chimpanzees in the wild.
Step Five: Avoid Predators
During the terminal phase of the Miocene era, or around five million years ago, the climate began to shift from wet subtropical to much more arid, grassland conditions. Over the next three million years, the heavy forest cover gradually died out and tree based hominid ancestors were forced down onto ground. There, they faced the most brutal lineup of predators in the world, including lions, leopards, hyenas, and possibly wild dogs in large packs. Survival in such environments is limited to either predator avoidance or running and hominids such as A.afarensis would have been vulnerable due to lack of swift movements necessary to escape predators. Bipedalism also exposed early hominids to predators by making them upright. They were forced to rely on binocular vision for predatory avoidance, but in cases where a predator was not seen, they were easy prey for ambush hunters. Also, their plant food diet increased their exposure to predators. The combination of other factors such as smaller body size, and lack of sharp teeth or claws also increased vulnerability of hominids to this fate. Only a few fossilised examples are available; according to the taphonomic studies of Hart and Sussman(2005), 5% of A. afarensis fossils show evidence of having been eaten.
The emergence of hominids become bipedal has without question was one of the biggest factors in the development of civilization. If our early ancestors had never left the trees, we would not be where we are today, or they wouldn’t have developed the way they did. By becoming bipedal it allowed them to travel greater distances and use their bodies in different ways. The bigger brain and the use of tools really allowed hominids to further the range of their existence and become more well rounded. There really cannot be enough said about the emergence of bipedalism. Civilization is directly a result of everything this ability allowed hominids to do.

An Essay on Foraging Societies

Foraging society forms the oldest and the more basic political system of people- the band societies. For more than 1 million years, these people from hunter-gathering societies sustain their living doing this. The contemporary hunter/ gatherers form a small group or population of people with little density and nomadic type of living.
Foragers remain egalitarian because they live in close kinship relations with others. They were tied with relations and they formed groups of unity. That is the reason why they exchange commodities or services among each other. The wealth circulated among themselves. This created an egalitarian group, where there were no great differences between people.
An example of a foraging society, residing in the Kalahari Desert, is the society of King San or the Bushmen. They gather fruits, berries, melons, and nuts. It is estimated that women gather the food and the overall time spend on gathering is 2 or 3 days out of one week. Men from the tribe spend their spare time in performing rituals, resting or entertaining. They reside in Namibia, Botswana, and South Africa.
An example of a foraging society in the tropical rain forests is the Mbuti Pygmies. In the gathering process everyone of the group is involved, even children- male pick up elephants, wild pigs and other animals, while females gather the vegetation.
The third group of foragers dwells in the arctic regions where vegetation was scarce. Eskimos, the local people, hunt sea mammals (whales, seals) and value a lot the undigested vegetation. For that reason, female did not specialize in gathering food. In the summer both males and females gathered larvae and maggots.
Fissioning among foraging people eccurs, when under certain conditions( like overpopulation) there is a need of migration of some people, and their fragmentation into smaller groups of people. Sometimes the subsistence food can become scarce, and not enough for the entire population.
Infanticide occurs when a mother deliberately kills a newly born child. The reason is that sometimes, woman cannot afford to meet the needs of the baby, or because the baby has some deformed physical features.
The fertility rate among foraging people is very low. There may be several reasons for this. Females from the San people are for example very slim and they do not weight more than 80 pounds. This can postpone the menstruation. Their puberty comes later, the average age is 16 years-old, compared to the average age in the US- 12years-old.
Most of the foraging groups do not differ in their economic state. They share the same economic system based on reciprocity, the exchange and sharing of goods, food, and services. It is called a Reciprocal Economic system. Most commonly, families exchange their food with other families from the group. It is defined that there are three types of reciprocity.
The first one is called Generalized Reciprocity, which is based on the assumptions that there is no return in the exchange. In other words, people do not expect to have a return for they favor, or exchange of goods or services. For example, it is even insulting among some foraging group to say thank you, after they have given you food. We also have in our societies Generalized Reciprocity- when your parents buy you clothes or give you pocket money, they do not expect you to return anything to them back.
This system creates more mutual trust and bounds better kin and relations. It also strengthens the egalitarian status of people.
The second type of Reciprocity is the Balanced Reciprocity. It involves an exchange with immediate return. This system is more like bargain and trade. It is used by groups of people who in a far distance between them. In modern foraging groups this reciprocity is not very common, because most of them exchange values and goods among kin groups only.
The third type is the Negative Reciprocity, which involves no reciprocity of all. It is an attempt to get an exchange or a deal without returning anything.
According to Lee and DeVore’s work, foraging people like the San are affluent in terms of their allocated time spent on finding subsistence. They estimated that foraging people easily find food enough for a couple of days, and that foraging people have adequate and well balanced diet. They called them Leisure and Affluent people. They found that the average death rate is not high and the average age of people from those societies is the same as people from more developed industrialized societies. According to another anthropologist Sahlins, foraging people did not accumulate goods and food, because of their nomadic living, and that makes them not so materially obsessed.
However, recent studies challenged the hypothesis mentioned above. They found that these facts to not apply to every forage group. For example in the rain forests people could not easily find some certain type of food immediately and spend more than 30 , 40 hours a week, searching for it. Furthermore, it is estimated that other activities, such as making weapons or preparing the food also involves much time. Those recent studies do not challenge entirely the previous hypothesis, but expand the relativity that comes from the geographic locations of people.
The social organization of foraging people is based on kinship, marriage, family, gender and age.
The family can be Nuclear, which includes parents and their immediate offspring. Band includes several Nuclear Families. A band can include from 20 to 100 individuals, depending on the environment capacity of subsistence of those people.
Cross cousin marriage appears when a male is married to the father’s sister’s daughter or his mother’s brother’s daughter.
Patrilocal residence- when the married couple resides with the male’s father.
Restricted marital exchange is the combination of patrilocal residence and cross cousin marriage, where two groups exchange the females to tight the kinship alliances.
Brideservice is when male resides in a female’s band for a period of time.
Matrilocal residence- the husband lives with the bride’s family.
Inuit tradition is the wife exchange where male individuals have sexual intercourse with each other’s wives.
Egalitarian status of men is more common than the equal status of females in foraging group, compared to people from other societies.
Patriarchal- when male dominates in political and social aspects.
Gender and Age are important factors in evaluating the labor division. They vary between societies to societie and determine the social stratification and hierarchy.
The warfare and violence in modern foraging societies differ from the past foraging socities. There are now lower at rate. Most of the problems that individual resolves are connected to relations between adultery.