Grass: In Search of Human Habitat (Organisms and Environments)

Grass In Search of Human Habitat Organisms and Environments In a richly drawn, anecdotally driven narrative, Joe C. Truett, a grasslands ecologist who.
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Organisms and Environments

Basic stone tools thus greatly enhanced the functions of teeth in a way that allowed access to an enormous variety of foods. These foods included meat from large animals, which was sliced from carcasses using sharp edges of flakes. Bones were broken open using stones to access the marrow inside. Other tools could be used to grind plants or to sharpen sticks to dig for tubers.

Tool use would have made it easier for hominins to obtain food from a variety of different sources. Tool use would have widened the diet of hominins. Meat, in particular, is a food that was obtainable in equivalent ways, with similar nutritional value, in virtually any type of habitat that early humans encountered. Although making simple toolmaking may have developed originally in one type of environment, the carrying of stone tools over considerable distances — and becoming reliant on stone technology — may have arisen due to the benefits of altering the diet as environments changed.

The oldest known stone technology — called Oldowan toolmaking — involved carrying rock over several kilometers and is found associated with a variety of ancient habitats.


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Redistributing stone and other resources, such as parts of animal carcasses, by transporting them may have helped hominins cope with variable habitats. As predicted by the variability selection hypothesis, hominins were not found solely in one kind of habitat, but rather in a variety. A major signal of the ability to tolerate different environments was the dispersal of the genus early Homo beyond Africa into Asian environments.

Early evidence of the diversity of Homo erectus environments in Asia includes the following sites:. In these locations, hominin groups encountered distinctly different environments, different plants and animals and foods, and different climatic conditions — a very wide range of temperature and strong variations in aridity and monsoonal rains.

Environmental instability may have been a factor not only in shaping adaptations but also in contributing to the extinction of some lineages. Environmental variability associated with the extinction of large mammal species has been proposed for the southern Kenya region. Sediments, stone artifacts, and animal faunal at the site of Olorgesailie span most of the past 1. Numerous environmental shifts are recorded in the Olorgesailie deposits.

The ancient lake level and its chemistry, for example, changed frequently, and sometimes the lake dried up, leaving small wetlands and streams as the main source of water in the basin.

Organisms and Environments - University of California Press

Volcanic eruptions also blanketed the landscape in ash, killing off grass and reshaping the properties of the ecosystem. An example of a hillside of sediments in the Olorgesailie region. The hillside, which represents about 10, years of time with a volcanic ash at its base dated around 1 million years ago, shows evidence of strong environmental shifts. Layers of sediments show the fluctuation between dry and wet environments and a time when volcanic ash covered the ancient landscape. Rick Potts studied the pattern of climatic turnover in the fauna and the occurrence of archeological sites at Olorgesailie and another site in southern Kenya, and found that several large mammal species that had previously dominated the fauna of this region went extinct between about , and , years ago, during a period of repeated environmental instability.

These species were replaced by modern relatives, which tended to be smaller in body size and not as specialized in diet or habitat. For example, the zebra Equus oldowayensis had large and tall teeth specialized for eating grass. Its last known appearance in the fossil record of southern Kenya is between , and , years ago; it was replaced by Equus grevyi , which can graze feed on grass as well as browse feed on leaves and other high-growing vegetation. The fossil baboon Theropithecus oswaldi , which weighed over 58 kg over It also went extinct between , and , years ago.

Its extant relative, Papio anubis , is omnivorous and moves easily on the ground and in trees. Two other large-bodied animals that specialized in eating grass, the elephant Elephas recki and the ancient pig Metridiochoerus , were also replaced by related species that were smaller and had more versatile diets Loxodonta africana and Phacochoerus aethiopicus. The aquatic specialist Hippopotamus gorgops was replaced by the living hippopotamus, which is capable of traversing long distances between water bodies. The replacement of the specialized species by closely related animals that possessed more flexible adaptations during a time of wide fluctuation in climate was a key piece of initial evidence that led to the variability selection hypothesis.

Although Acheulean toolmaking hominins were able to cope with changing habitats throughout much of the Olorgesailie record, the Acheulean way of life disappeared from the region sometime between , and , years ago, perhaps also a casualty of strong environmental uncertainty and changing circumstances. Brain enlargement during human evolution has been dramatic. During the first four million years of human evolution, brain size increased very slowly. Encephalization, or the evolutionary enlargement of the brain relative to body size, was especially pronounced over the past , years, coinciding with the period of strongest climate fluctuation worldwide.

Larger brains allowed hominins to process and store information, to plan ahead, and to solve abstract problems. A large brain able to produce versatile solutions to new and diverse survival challenges was, according to the variability selection hypothesis, favored with an increase in the range of environments hominins confronted over time and space.

After , years ago, hominins found new ways of coping with the environment by creating a variety of different tools. In some parts of Africa, a shift occurred in which a technology dominated by large cutting tools was replaced by smaller, more diverse toolkits. Technological innovations began to appear in the Middle Stone Age in Africa, with some early examples dating prior to , years ago. Some of the new tools provided ways for hominins to access food in new ways. Points were hafted, or attached to handles such as spear or arrow shafts, and were later used as part of projectile weapons, which allowed hominins to hunt fast and dangerous prey without approaching as closely.

Barbed points were used to spear fish. Barbed points made from bone were found at the site of Katanda, in the Democratic Republic of the Congo, along with the remains of huge catfish. Grindstones were used to process plant foods. Other tools were used to make clothing which would have been important for hominins in cold environments. Over the past , years or so, the direct ancestors of living humans developed the capacity to create new and diverse tools. Archeological discoveries show that wider social networks began to arise, enabling the transfer of stone material over long distances.


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Symbolic artifacts connoting complex language and the ability to plan are also evident in the archeological record of the Middle Stone Age of Africa. These findings indicate an improved capacity to adjust to new environments. Most of the past , years in East Africa was a time of strong climate oscillation. The timeline at the bottom of the image is , to 40, years ago right to left. Trading between groups to obtain materials and to cement alliances is a hallmark of modern human behavior.

Larger brains and symbolic ability facilitated more complex social interactions. By , years ago, hominins were exchanging materials over distances of over km. The social bonds that were forged by exchanging materials between groups may have been critical for survival during times of environmental change when one group relied on the resources or territories of a distant group.

Modern foragers use social ties to mitigate the effects of famines and droughts. Evidence of the human capacity for communication using symbols is apparent in the archeological record back to at least , years old, and probably older. The use of color, incised symbols, decorative objects, and language are part of this capacity for communication. Symbolic communication may be linked with information storage.

Language is an essential part of modern human communication. Language makes it possible to convey complex ideas to others. Communication of ideas and circumstances via language would have made survival in a changing world much easier.

Adaptations, interdependence and competition

However, there is no fossil evidence for words and grammar that are the direct hallmarks of human language. Preserved pieces of pigment are one of the earliest forms of symbolic communication. Ocher and manganese can be used to color objects and skin. Paintings and drawings were also used to represent the natural world. Use of symbols is ultimately connected to the human ability to plan, record information, and imagine.

Neanderthal populations Homo neanderthalensis in Europe endured many environmental changes, including large shifts in climate between glacial and interglacial conditions, while living in a habitat that was colder overall than settings where most other hominin species lived. Some of the environmental shifts they endured involved rapid swings between cold and warm climate.

Animal Habitats

The Neanderthals were able to adjust their behavior to fit the circumstances. During cold, glacial periods, they focused on hunting reindeer, which are cold-adapted animals. During warmer, interglacial periods, they hunted red deer. During extreme cold periods, they shifted their range southwards toward warmer environments. Neanderthals and modern humans had different ways of dealing with environmental fluctuation and the survival challenges it posed. Modern humans, Homo sapiens , had specialized tools to extract a variety of dietary resources.

They also had broad social networks as shown by the exchange of goods over a long distance. They used symbols as a means of communicating and storing information. Neanderthals did not make tools that were as specialized as those of modern humans who moved from Africa into Europe sometime around 46, years ago. The Neanderthals usually did not exchange materials over so wide a distance as Homo sapiens. They occasionally produced symbolic artifacts. Despite many climatic fluctuations, modern humans were able to expand their range over Europe and Asia, and into new areas such as Australia and the Americas.

This evidence suggests that adaptability to varying environments was one of the key differences between these two evolutionary cousins. During the time when Neanderthals evolved in Europe, global climate fluctuated dramatically between warm and cold. The highlighted area on the right side of the graph represents the last , years. Overall, the evidence shows that hominins were able to adapt to changing environments to different degrees.

The genus Homo , to which our species belongs, had the capacity to adjust to a variety of environmental conditions, and Homo sapiens is especially able to cope with a broad range of climatic conditions, hot and cold environments, arid and moist ones, and with all kinds of varying vegetation. We use resources from a vast variety of plants and animals and use many specialized tools. We have many social contacts and means of exchanging resources and information to help us survive in a constantly changing world.

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The idea that the major adaptations in our evolutionary history arose in response to environmental variability and shifting selection pressures variability selection leads to a new understanding of human evolution. The figure above illustrates how the emergence of human characteristics from 6 million years ago to present conferred benefits that improved the ability of our ancestors to survive unpredictable and novel environments.

Humans today represent the one species that has survived from the diversity of hominin species. Despite their very close relationship with our species, and despite the fact that all of them possessed some combination of features that characterize humans today, these earlier species and their ways of life are now extinct. The intensity of environmental change seems likely to create entirely new survival challenges for the lone hominin species on the planet, and many other organisms as well.

Species Fossils Mystery Skull Interactive. I Came From Where? Imagining the Human Future video Public Event: Religious Audiences and the Topic of Evolution: An ecosystem is the interaction between a community of living organisms and their environment. A community is two or more populations of organisms. An ecosystem is two or more populations of organisms usually many more in their environment. A population is all the organisms of the same or closely-related species in an area.

Levels of organisation within an ecosystem Organisms within an ecosystem are organised into levels. Producer Producers are plants and algae, which photosynthesise. Primary consumer Primary consumers are herbivores, which eat producers. Secondary consumer Secondary consumers are carnivores, which eat primary consumers. Tertiary consumer Tertiary consumers are also carnivores. They eat secondary consumers. A woodland ecosystem showing the habitats of different species. Interdependence All organisms in an ecosystem depend upon each other.

Competition All photosynthesising plants and algae in an ecosystem compete for light, space, water and minerals from the soil. Stable communities A stable community is one in which the size of the populations of all species remain relatively constant over time.

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Producers are plants and algae, which photosynthesise. Primary consumers are herbivores, which eat producers. Secondary consumers are carnivores, which eat primary consumers. Tertiary consumers are also carnivores.