2. What is the pulsed climate variability hypothesis and what evidence do these scholars provide to support this theory?
3. Are there limits to the scientists' knowledge about human evolution? Provide a few examples.
4. There has been much debate about the chronology of the Ain Hanech Formation in North Africa. What methods do these scholars use to come to their conclusions and whose work are they supporting with this evidence?
5.What is the "Green Sahara" and what are the problems with this hypothesis? What do these scholars present as an alternative hypothesis?
1. Understanding climate is essential because Africa is the area where scientist believe most species originated. While hominins have been dispersed throughout the world, the majority of species originated in Africa. With that being said, the environmental factors in Africa play a direct role in the adaptation of different species. Therefore, the environmental factors in Africa had a direct impact on the development of most species.
ReplyDelete2. The pulsed climate variability hypothesis explains the effects of short periods of extreme climate variability in hominin evolution in East Africa. Scholars provide palaeoclimate evidence for the pulsed climate variability hypothesis, which helps to explain how theories an be applied in new context.
3. There are major limits to scientist’s knowledge about human evolution. One is the exact timing and altitude of uplifts in Africa. Tectonic plates in Africa, which created The East African Rift, have a large effect on the climate of Africa. This effects the rainfall patterns and overall evolution of African climate, the exact rates of uplift and the altitude are unknown to scientist. Another limit to scientist’s knowledge is the effect tectonics had on vegetation. Scientists have very little knowledge of when forest or grasslands formed, therefore limiting their knowledge of the wider environmental climate pattern. Another limit in understanding the effects of global climate change in Africa in the lack of high resolution continental records. Exposure and other factors make it difficult for scientists to construct ages of sediments and ect.
4. To come to their conclusions about Ain Hanech scientists collected fresh samples by excavating trenches on the west margin of the Qued Boucherit. Samples and evidence were collected at each site and transported properly. Different methods and analysis tools were used to process the specimens found. With their new evidence scholars support previous work by Sahnouni et al and Sahnouni and de Heinzelin.
5. The Green Sahara refers to when the Sahara when it was environmentally enhanced because of increased water availability. This hypothesis suggests circumstantial evidence that large mammals were dispersed throughout Africa. The actual structure and variation of population in Africa is unknown. Scholars present as an alternative hypothesis that the Sahara underwent environmental enhancements, therefore the desert was transformed into savannah and grasslands.
1. Understanding the climate of East Africa is essential to any historian's analysis of our origin because it provides direct evidence of how the population and distinction between early humans was designated. Environmental conditions (in any period) dictate how, where, why, and when anyone will populate a certain region of the world. The authors state that environmental variability explains why and how the hominid population spectated and moved the way it did.
ReplyDelete2. The pulsed climate variability hypothesis, according to the authors, was formulated to provide an explanation as to how climate changes and variability effected difference specie in Africa. The authors provide multiple pieces of evidence including maps and tables to back up the hypothesis.
3. The authors provide multiple limits to their knowledge regarding human evolution: fossil records collected contains gaps, insecurity as to where hominid species evolved, and an inability to calculate exact tectonic movements such as uplift. The rate of uplift is significant because it determines the severity of possible rain shadows that form on the side of mountains, which is essential knowledge when determining whether or not a population thrived.
4. Scientist at Ain Hanech obtained samples from the site through a laborious process of determining magnetic polarity, using bulldozers to dig trenches, using a ceramic knife and sodium silicate solution to extract the sample, and 63 specimens were then studied. The work supported by the scientists was authored by Sahnouni and Heinzelin.
5. The Green Sahara is a term referring to a period of time when the area experienced higher water levels. The scholars state that the problem with the hypothesis is that the evidence is almost entirely circumstantial; in other words, there is not nearly enough hard-evidence to back it up. The alternative hypothesis is more focused on cultural diffusion, through successive budding. The difference in between the original and alternative hypothesis is not seemingly significant. However, through tests and paleomagnetic studies, the authors are able to come to their conclusion that the division among the populations was long-standing.
According to the authors, understanding the climate of East Africa is essential because it is here that our species, homo sapiens sapiens, originated. Key events in hominid evolution such as bipedalism and brain expansion occurred in this single region of the world. Although fossils of hominids have been found throughout the world, there is evidence to suggest that these people migrated from eastern Africa. The climate or environment a species is in affects its evolutionary progress. Therefore, the idea is that understanding the environment in which hominids evolved will to understand human evolution.
ReplyDeleteThe pulsed climate variability hypothesis states that extreme climate change in East Africa directly led to hominin evolutionary traits such as bipedalism. Evidence cited earlier in the paragraph includes paleoanthropological evidence that corresponds more closely with this hypothesis versus past ones.
There are two components of evolution that the scientists’ have not yet figured out. The first component is the “timing and altitude” of the tectonic shifts. Understanding altitudes is essential in understanding rainfall; without which, they cannot fully understand the climate. The second component is the amount that plate tectonics affected vegetation, another factor essential to providing a complete picture of human evolution. Without knowing when grasslands triumphed over forests, it is impossible to discern exactly when hominids developed bipedalism.
The scholars came to their conclusions by collecting fresh samples for a paleo magnetic study. They dug a hole over ten feet deep, and dug out clay-rich sediment in various sized pieces. Sodium silicate was then injected into the sediment for hardening, before being carefully wrapped and taken to the lab for analysis. The scholars work supports the evidence of Sahnouni, and invalidate Geraads.
The “Green Sahara” is a hypothesis that the Sahara once had abundant vegetation due to increased water access. The first problem with this hypothesis is that an isotope called MIS-16 has revealed that regions of the Sahara have always been a desert, and have never have abundant water access. The second issue with the theory is that there is archaeological evidence that hominids used tools adapted for various environments. The alternative hypothesis is that environmental changes such as increased rainfall for periods of a time led to a diversification of species as the desert was transformed into a savannah-like grassland.
1) Understanding the climate of East Africa is essential because East Africa is the direct source of evolution. Scientists believe that the climate is what caused different species to adapt and evolve. Understanding the environmental factors in East Africa can help scientists understand why certain hominids migrated to different parts of the world from Africa.
ReplyDelete2) The pulsed climate variability hypothesis says that extreme weather conditions in East Africa let to different species migrating and evolving. There is evidence such as fossil records of early hominids to support this theory.
3) Scientists' knowledge is very limited right now. There is no evidence that points to exactly where these different species came from or what caused them; everything is just a theory. There are also gaps in fossil records so no one really knows when earlier species started to evolve to be like the modern human.
4) Scholars dug trenches to uncover specimens and evidence. They then carefully brought the evidence to a lab to study. Their evidence supports Sahnouni.
5) The Green Sahara refers to when the Sahara had more green vegetation due to more water availability. There have been discoveries that show that the Sahara has always had a desert climate which means that water would not be available. The alternative hypothesis would be that there was some other extreme climate change that led species to evolve.
1.) The climate of East Africa is essential in human evolution because that is believed to be where our species originated. Climate is an important factor in determining how the different species evolved. The species would have to learn and adapt to their given environment to survive, so the evolution of the hominid species has a direct relationship with its environment and climate. Environmental variability is an explanation for why and how the hominid population migrated.
ReplyDelete2.) The pulsed climate variability hypothesis states that extreme changes in climate in East Africa led to the differentiation in evolutionary traits. Maps, tables, and other evidence is provided by the authors.
3.)There are multiple limits associated with the knowledge of human evolution. One example is the timing and altitude of tectonic shifts. The rates of uplift are unknown, so the effects of rainfall patterns are also unknown. It also affected vegetation in the area, which is essential in understanding evolution regarding climate. Scientist are uncertain when forest and grasslands formed, which could heavily relate to evolution.
4.) The Ain Hanech scientist collected fresh samples by digging trenches, and using tools and sodium silicate to extract the samples. After proper analysis in a lab, evidence supports the work of Sahnouni and Heinzelin.
5.) The Green Sahara refers to the Sahara during a period of increases water availability. The hypothesis suggest there was abundant vegetation with large mammals roaming throughout. An isotope found reveals that some regions of the Sahara have always been desert. There is not enough evidence to prove this theory correct. The alternative hypothesis suggest that increased rainfall led to greater diversification and grasslands that resemble a savannah.
1. Current evidence suggests that all major events in early hominin evolution came out of East Africa. Scientists are therefore eager to study the climate of that region because they believe that change in climate was a leading factor that directly correlates with how and when early hominids evolved and adapted to the world around them.
ReplyDelete2. The pulsed climate variability hypothesis details the relationship in which how short periods of extreme climate change in East Africa altered hominin evolution. Paleoclimate evidence has been used to back up this hypothesis such as early hominin remains and sedentary samples from the region.
3. There are absolutely limits and restrictions to scientists studying the change in climate in Africa. One major restriction is the lack of knowledge concerning the timing and tectonic features of the regional uplift. Another limit is the uncertainty surrounding the effects tectonic shifts had on East Africa's vegetation.
4. Scientists had to use laborious and careful measures to fulfill their research at the Ain Hanech location. They dug trenches and holes in order to expose sediment and then had to inject a silicate compound into the sediment for it to be safely extracted. the evidence obtained from the sediment samples prove the earlier work of Sahnouni.
5. The Green Sahara hypothesis sets forth a claim that the Sahara once had higher water levels which would translate to mean more vegetation as well. There is little evidence to back this up though because new discoveries and testing has proven that some parts of the Sahara have always maintained a desert climate, thus meaning that water was never there. As a result, a new hypothesis was developed that worked to detail the process through which the desert eventually transformed into what we now know as the savannah and grasslands.
1. It is important to understand the climate of East Africa because it is important to know how early hominids would have had to adapt to a changing climate in order to survive.
ReplyDelete2.The Pulsed Climate Variability hypothesis explains how short "pulses" or periods of climate change affected hominin evolution. Map and sedentary samples have been used to back this up.
3. Yes, there are limits to scientests knowledge. There's no way to prove exactly where hominins started out at or at what rate the environment changed to affect the adaptation of hominins.
4. Scientists dug trenches and gathered samples and did several tests to support the work of Sahnouni and Heinzelin.
5.The Green sahara refers to a time when the Sahara Desert was a lush green climate with large mammals inhabiting the region. New testing has shown that some parts of the Sahara have always been a desert climate, and a new hypothesis was created that stated the desert turned into what is now the savannah and grasslands.
1. The authors state the main reason the understanding of climate is important is the climate's effect on development and evolution of homo sapiens. Crucial events that shaped the evolution can be directly traced back to the affects of climate in the african region during homo sapient development. The climatic patterns of Africa also influenced where and how the homo sapiens of the era settled and lived. For example, as stated in class, with climate changes shifting towards savannas Bipedalism became a more energy efficient solution to travel. These are the reasons that understanding the climate of the region is exceptionally important when studying the evolution and cultural settling of a people in an area.
ReplyDelete2.The pulsed climate variability hypothesis is a hypothesis that ponders the importance of extreme climate change and its affect on the evolution of early hominids. The evidence that the authors cite is based on paleoanthropological discoveries that support the claim that climate change was even responsible for adaptations such as bipedalism.
3. The articles are able to pinpoint major limits in regards to the claims they can make about the ancient African hominid development. For instance, some of these limits come in the form of fossil records and the fact that they aren't scientifically 'complete'. Another factor that the researches cannot account for are tectonic movements, this is problematic because the landscape in the time of hominid development could've been drastically altered depending on past tectonic movements. In regards to the last point, without knowing exactly what the landscape looked like, its hard to pinpoint what the environment the hominids developed in was like, and it is also hard to pinpoint their exact developing location.
4. The scientists were able to come to their conclusions after individual studies at many different sites utilizing a process backed by magnetic polarity to obtain samples. These samples were then all taken and analyzed together after the specimens were treated properly. The work that the scientists discovered was most correct was the work of Sahnouni and Heinzelin.
5. The green Sahara hypothesis is a theory that the Sahara once was a green grassland due to the availability of rainfall. This rainfall made the Sahara a lush land teeming with plant life. This theory has holes though in the form of many scientific findings presenting evidence that the Sahara was always a desert never full of plant life. The alternative hypothesis that was presented by researchers is that the environment had gone through copious changes including, but not limited to, increased rainfall through the eras the allowed for many species to flourish in the Sahara.
1. Understanding the climate in East Africa is essential because it is believed to be the the origin point of a majority of human species. Due to the fact that climate is thought to play a key role in hominin speciation and adaption, it is vital to understand the climate of East Africa to better understand human evolution as a whole.
ReplyDelete2. The pulsed climate variability hypothesis reveals the importance of extreme climate changes specific to East Africa in hominin evolution. The author uses climate model simulations and maps/tables as evidence to support the hypothesis.
3. There are major limits to scientific knowledge of evolution. Regional tectonics are not completely understood such as the exact timing and uplift altitude. These factors play a major role in understanding rainfall patterns in Africa and the climate as a whole. As climate plays a major role in human evolution, it is a major limit to understanding hominin development in its entirety. Another limit is the impact that tectonics had on vegetation, which is also vital in understanding hominin evolution.
4. The scholars took a fresh set of samples by digging a trench and taking small oriented blocks. The procedure was the same for each sample regardless of size; they used a ceramic knife to carve a surface and then put a sodium silicate solution in it and let it dry. Once the blocks were removed they wrapped the samples in parafilm paper and sent them to a lab. The end results support the previous results found by Sahnouni and Heinzelin.
5. The Green Sahara hypothesis refers to a time in which the Sahara had increased water availability and vegetation. Evidence shows that areas of the Sahara have always been arid and desert like, this goes against the Green Sahara hypothesis completely. A new hypothesis was created which says that increased rainfall led to a diversification of species which were longstanding (lithic analysis) and led to the grasslands.
1.Understanding the climate of East Africa is essential to gaining knowledge of the evolution of human species because the climate change is controlled by the tectonics of the Eastern Rift Valley.These Rift changes were responsible for not only the altering of climate, but the formation of vegetation, hydrology, and species alike.
ReplyDelete2.The Pulse climate variability hypothesis suggests that drastic climate changes over different periods of time directly effected the evolution of hominins. The evidence for this is shown through charts explaining sudden changes in environments and the East African region as a whole.
3. While there has been impressive progress in gaining knowledge on evolution, scientists knowledge is limited in several ways. Scientists are starting to find links between certain things ( such as orbital forcing and African climate). The only way to be able to gain knowledge on these connections is by finding more evidence, but even with evidence, dating certain events within the region is difficult.
4.A method that is being used is the extraction of sediment samples from both Ain Hanech and Oued boucherit and attempting to establish magnetic polarity. By doing this, they could attempt to establish chronology through paleomagnetic analysis. This work is supporting research by Sahnouni.
5.The Green Sahara Hypothesis is the thought that the Sahara was once a region of lush vegetation and water sources when the region underwent environmental amelioration.Research has indicated that humans with in the region were associated with several different types of environments. Because of this knowledge, new hypotheses have been formed to indicate how the desert may have transformed into the grasslands and savannah we see today.
1.) Being able to understand the climate of East Africa gives a better insight of how hominin's evolved and adapted to live. Meaning the authors wanted readers to see what major climate changes did to evolution of modern days Homo Sapiens.
ReplyDelete2.) The Pulsed Climate Variability Hypothesis is the overall understanding of the paleoclimate of East Africa and helps us construct a model of evolutionary changes in early human studies. Early scholars supported this hypothesis with models and giving us brief over views of the climate and how that climate changed Hominin's everyday life.
3.) In the article there are points made that limits are set do to uncertain climate changes do to lack of fossil evidence and the unknown tectonic movements that happened during early human periods.
4.) First scholars would take a bulldozer and dig along the ridge to collect fresh samples; each sample being exactly the same in size, shape and density. Then ceramic knife was taken to the samples carving a horizontal surface and penetrated with a solution of sodium silicate, which was then set to dry for hardening.
5.) The Green Sahara Hypothesis describes a time when it was full of vegetation, massive rivers and animals of all kind. Meaning that it had consistent rainfalls and lushes grasslands. But in fact scholars have found holes in that hypothesis and discovered that is was always a dry/arid place, with little to no vegetation alive.
1. According to the authors, why is understanding the climate of East Africa essential?
ReplyDeleteUnderstanding East African climate is important because it allows us to gain insight to the evolution of the human species. Due to the plate tectonics of the Great Rift Valley, the climate has been changed along with sources of food and water. This, in turn, has changed the evolution of the human species.
2. What is the pulsed climate variability hypothesis and what evidence do these scholars provide to support this theory?
The Pulsed Climate Variability Hypothesis shows the climate change in different time periods affect the evolution of East African hominins. The evidence provided consists of samples of remains and explanations of climate change.
3. Are there limits to the scientists' knowledge about human evolution? Provide a few examples.
Limits to scientific knowledge include a gap in the fossil record, the inability to pinpoint accurate dates for some things, and the fact that all of the ideas the scientists have about where the species come from and when they began to evolve into modern humans is all theory,
4. There has been much debate about the chronology of the Ain Hanech Formation in North Africa. What methods do these scholars use to come to their conclusions and whose work are they supporting with this evidence?
Scientists extract samples by digging trenches. After the samples are extracted, they are tested. The tests support the work of Sahnouni and Heinzelin
5.What is the "Green Sahara" and what are the problems with this hypothesis? What do these scholars present as an alternative hypothesis?
The Green Sahara is the idea that the Sahara used to be very alive and had ample vegetation. Research shows that the Sahara actually used to contain multiple types of environments and different types. The alternate hypothesis is that increased rainfall allowed some species to thrive in the Sahara for certain periods of time.
1. Understanding the climate of East Africa is essential in terms of following the evidence which indicates that all hominin species can be traced back to East Africa. There are many theories that discuss hominid evolution and dispersal out of Africa. Understanding the circumstances in which these species were trying to survive plays a critical role in how the theories that surround the dispersal were developed.
ReplyDelete2. According to the authors, the pulsed climate variability hypothesis explains the role of short periods of extreme climate variability within East Africa as the main driving force of hominin evolution. The use of palaeoclimate evidence helps further explain the hypothesis.
3. There are many limits to the scientists’ knowledge about human evolution discussed by the authors. Some examples include: the exact timing and altitude of the uplift within Africa, the effects that the East African Rift have on the climate in Africa, fossil records, and the effects that tectonics had on vegetation.
4. While studying the Ain Hanech Formation, the scientists excavated the site by digging trenches, taking samples, and then carefully transporting them to a lab for a paleo magnetic study. The work of these scientists supports Sahnouni while invalidating Geraads.
5. The Green Sahara is the idea that the Sahara had increased water availability which leg to an increase in vegetation. However, problems with this hypothesis. Hooghiemstra et al using the presence of arid pollen in cores off the Northwest African coast since Marine Isotope Stage to explain that regions of desert have always existed within the Sahara. Instead of the Green Sahara hypothesis, scholars introduced the idea that environmental enhancements occurred throughout the Sarach which transformed it into savannah and grasslands.
1.) The climate of the environment that a species occupies affects its evolution. This is why according to the authors it is of great importance to understand the East African climate because here our ancestors homo sapiens sapiens originated. Bipedalism and the enlargement of the brain are all evolutionary traits that occurred because of the climate of the environment, therefore, better understanding the climate helps us to better understand how hominids evolved.
ReplyDelete2.) The pulsed climate variability hypothesis helps to explain how short periods of extreme climate variation affects the hominin evolution of East Africa. Palaeoclimate evidence, maps and tables are provided to back up the hypothesis.
3.) The knowledge possessed right now is limited. There is no conclusive evidence that shows exactly where different species originated from. Gaps in the fossil record also make it burdensome to pinpoint when the earlier species began to evolve to resemble modern humans.
4.) At the Ain Hanech location scientist excavated trenches and holes. This exposed the sedimentary layer underneath and with the infusion of sodium silicate were able to extract it. The sediment samples supported the work of Sahnouni and Heinzelin.
5.) The Green Sahara hypothesis is a hypothesis that states due to increased water availability the sahara was once a green grassland with increased vegetation. However, evidence shows the regions of the sahara were always dry, arid and desert like. This contradicts the Green Sahara hypothesis. The alternate hypothesis is that the region has gone through an abundance of changes including increased rainfall which allowed for many species to thrive.
1) Understanding the climate of Africa is important because East Africa is the source of evolution and having an understanding of the climate will give us a greater understanding of what drove out the hominins from East Africa to other parts of the world.
ReplyDelete2) The pulsed climate variability hypothesis explains helps to explain the effect of short periods of extreme climate variability of East Africa during the hominin evolution. The scholars used paleo-climate evidence to support their hypothesis.
3) There are absolutely limits to the knowledge about human evolution. A few examples are 1) The fossil records have gaps in them, 2) Having a good understanding of plate tectonics will help us understand how the climate changed and how it directly affected the evolution, and 3) Knowing how and when the grasslands started to become the dominant landscape of East Africa.
4) The scholars use the polar-magnetic studies to come to their conclusions. The scholars are supporting Sahnouni and Heinzelin with their evidence.
5) The “Green Sahara” refers to when the Sahara landscape had much more luscious and green vegetation due to the higher water levels in the environment. Some problems with the hypothesis are that the scholars state that the evidence is circumstantial and does not back up the theory. The scholars say that the Sahara went through environmental changes and overtime transformed into grasslands.
1. It is essential to study the climate of East Africa because, as stated in the Quaternary Science Review (page 11 of the Bel-Jean packet), there is reason to believe that the majority of hominin species originated in East Africa. Human evolution is shaped by climate changes because climate affects vegetation. Only those who adapt to be able to survive climate change and thrive will live on. So we will better understand the history of hominins by observing closely the weather history of East Africa.
ReplyDelete2. The Pulsed Climate Variability Hypothesis is an advanced environmental theory used to explain the evolution of hominins to bipedalism. This theory highlights the role of short periods of extreme climate variability specific to East Africa in driving evolution (page 12). It is originally derived from the aridity hypothesis, which states that rising temperatures shrank vegetation and left a large distance between food sources, and only those hominins who could get from place to place without using much energy could survive.
3. There are multiple limits to the current knowledge scientists have about human evolution, which are explained on page 15 of the Bel-Jean packet. For instance, tectonic uplift rates are still not completely understood. These affect rainfall so it is unknown when the climate changes actually occurred. It is also unknown to scientists what affects the tectonic movements had on vegetation, which is a major factor of survival and evolution for a species.
4. Scientists at Ain Hanech collected fresh samples by digging deep 1.5m wide trenches and taking the samples to the field as small blocks. Samples were wrapped in parafilm paper and shipped to the lab to be tested. The results supported the findings of Sahnouni et al and Sahnouni and de Heinzelin.
5. The “Green Sahara” is a term used to describe a time when the Sahara desert had an adequate water source to sustain vegetation. During this period, the entire desert was transformed into savannah and grasslands. Evidence shows that the Sahara has always had a temperature incapable of supporting vast vegetation. The alternative hypothesis would be that rainfall increased in the area and grasslands formed close by.
1. Understanding the climate of East Africa is important, as that is the consensus location for the origins of modern humans. Knowing what the climate was can explain a great deal about how and why hominids evolved the way they did.
ReplyDelete2.The pulsed climate variability hypothesis holds that short periods of extreme climate events were a key part of homonid evolution. Paleoclimatic and fossils are used to provide support for it.
3. As with most things, there are limits to what we know. The biggest thing is that essentially all of the information we have now is theory. It hasn't been proven yet, and likely can't be. Other problems include dating methods being somewhat imprecise, as well as an somewhat-incomplete fossil record.
4. The methods used by the authors was to remove material from trenches dug in order to expose older (unexposed) material, which was then studied to ascertain the paleomagnetic siganture of the materials. The work appears to support Sahnouni and de Heunzelin.
5. The green Sahara theory holds that the Sahara was at one time a good deal wetter and as a result much less hostile to life. The problem is that the current evidence does not appear to support the hypothesis as it is. The authors instead advocate a more gradual transition from a somewhat wet climate to the more dry one prevalent today.
1. Understanding the climate of East Africa is important because it played a major part of the first ancestors of humans and could have directly helped determine the evolutionary pattern of these ancestors. The climate is a large reason why most theorists believe the first humans originated here and why they migrated out of the continent eventually.
ReplyDelete2. The pulse climate variability hypothesis suggests that there was a long term climate change in East Africa filled with short periods of varying or wet climate and that this overall change led to many species in the region evolving and moving as a direct result. Scientists link data such as estimated lake levels and dust deposition in the Mediterranean with the evolutionary progress of hominins as evidence for this theory.
3. Scientists are limited in their knowledge of evolution with the fact that there is a large gap (500,000 years) in cranial capacity data of the hominins which complicates information on their diversity. There are also inconsistencies between continental and oceanic climate information that makes habitat reconstruction of the time period difficult.
4. Scientists dug trenches in the ground in order to excavate blocks of sediment which were then shipped back to laboratories for examination. From the evidence scientists were able to draw conclusions that supported the results of Sahnouni et al and Sahnouni and de Heinzelin.
5. The Green Sahara is a theory that suggests the Sahara Desert region used to much more habitable due to an abundance of water resources. There is evidence that shows that the Sahara region has always had a desert climate. An alternate hypothesis states that successive budding of organisms across the region is why artifacts of that time period were found there.
1.The climate of East Africa is essential because the variable local climate drives human ancestors to go out of Africa.Understanding of different climates in different can help us know how human ancestors lived and evolved.
ReplyDelete2.The pulsed climate variability hypothesis is a theory that think climate s drive human ancestors to evolve. One example in the book is Plio-Pleistocene lake.This article also provide statistic graphs(fig6,7) as reference.
3.The first limit is that the fossil record is not complete. We don't have any fossil between 2-2.5 MA. Another limit is a unsure number of the diversity pattern.
4. Scientists collect sample in the Ain Hanech and sent to the lab to get their texts checked. the evidence they got support the work that was done in Sahnouni and Heinzelin.
5. Green Sahara is a hypothesis that people think that Sahara used to be a place with savannah and grasslands due to the temperature and the rainfall.However,the problem is that there isn't enough evidence to prove this hypothesis. The alternative hypothesis indicate that if there is enough rainfall, the species in Sahara will increase.
According to the authors, understanding the climate of East Africa is essential as it provides key findings for the development of the study of evolution. Identified correlations between climate change such as the appearance or disappearance of lakes in the geographical history of East Africa and developments in human evolution such as the appearance of larger brains in species preceding homosapiens illustrate the need for a thorough understanding of East African climate as a key to understanding homosapiens sapiens’ evolutionary history.
ReplyDeleteThe pulsed climate variability hypothesis is considered a “framework” by the authors in which to further investigate the effects of climate change on evolutionary development and dispersal. The pulsed climate variability hypothesis is not a mechanism for evolutionary progress, but rather considers multiple mechanisms to be viable causes of evolutionary progress. An explanation of these mechanisms, along with a long explanation of the complex history of the East African climate and a thorough explanation of the limits of modern knowledge, is used as evidence for the pulsed climate variability hypothesis.
There are limits to the scientists’ knowledge on human evolution. One such limit is quite explicitly mentioned: the fossil record is incomplete and lacks data from significant time periods that would complete the evolutionary time table. And if we are to agree that the East African climate is essential to understanding evolution, it should be noted another explicitly mentioned limit in knowledge on evolution may be attributed to an impediment in obtaining high-resolution continental records. With resolutions generally greater than oceanic records, it is noted by the scientists that continental records can be vague and lump data from two distinct climatic periods into one category.
These scholars use a magnetostratigraphic and rock magnetic study to determine the age of the Ain Hanech Formation. Taking samples from the site and conduction these tests of magnetism, the scientists came to support the dating of the tools to the Olduvai Chron, thus backing the original findings from Sahnouni and de Heinzelin.
The “Green Sahara” is a hypothesis stating that there was no obstacle (i.e. desert) that posed a threat to human dispersal out of Sub-Saharan Africa due to increased water levels (and therefore greater vegetation diversification). There are multiple issues with this supposition beginning with that arid pollen of the Northwestern coast of Africa indicates that desert has always existed in the supposed “Green Sahara” region- defying a key component of the “Green Sahara” hypothesis. Besides this, it is indicated that there is an unclear correlation between the ecology and archaeology of Northern Africa, making an assessment of the extent of a “Green Sahara” rather difficult. As an alternative hypothesis, the scholars suggest that increased rainfall created more grasslands and thereby led to greater species diversification amongst populations in North Africa.
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ReplyDelete1. As one historian famously said,"those who do not know history are doomed to repeat it." It is important to understand the climate of East Africa to study the trends that led to events such as the shifting of tectonic plates, primates changing their walking habits (from walking on all fours to walking upright), and the dispersion of the hominids from East Africa. According to scientists, it is important to understand the climate of East Africa because this is where mankind originated. It is also important to understand the climate of East Africa so professionals can predict future trends.
ReplyDelete2.The Pulsed Climate Variability Hypothesis suggests that the drying trend in East Africa was due to extreme humidity, which drove the hominid evolution. Scholars support this theory with paleoclimate evidence.
3.With any theory comes discrepancies. There are a few limits in scientists' knowledge about human evolution such as the regional tectonic plates. Although scientists know exactly what caused East Africa to dry, they do not know when it occurred or how fast.The second topic that scientists have limited information on is the effect of tectonics on vegetation.
4.To come to conclusions about the debates of Ain Hanech Formation in North Africa, scholars carried out a paleomagnetic and rock magnetic study. They are supporting the works of Arambourg, who first reported the Ain Hanech site with evidence.
5.Green Sahara is "when the Sahara was environmentally ameliorated due to increased water availability." Basically, the Sahara became less of a desert and increased in vegetation. The problems with this hypothesis is that it is highly controversial and there is not enough substantial evidence to back this theory. As an alternative hypothesis, scholars suggest human populations in the region were associated with a range of different environments.
1)East African climate is important to human evolution in that scientists believe the ancient climate changes, such as tectonic activity and aridification, had a significant effect on hominin evolution.
ReplyDelete2)The pulsed climate variability hypothesis states that short periods of extreme climate variability drove hominin evolution in East Africa. They evidence tectonic activity in East Africa, such as the updoming and downwarping which created the East African Rift Valley, which created a system of lakes that periodically filled and dried. Hominin populations in turn migrated or dispersed in response to the filling and drying of the lakes, and some of these events, such as the formation of deepwater lakes, seem to be correlated with increases in hominin brain size.
3) There is debate over where geographically hominins developed and dispersed from. As the article points out, although there is a great deal of evidence for East Africa, other researchers suggest South Africa, Europe and Asia as other possibilities for hominin evolution.
4)When questioning the chronology of Ain Hanech, some researchers debate the analytical methods used in the interpretation of paleomagnetic analysis as well as stating that the material itself at Ain Hanech is not suitable for paleomagnetic analysis.
5)The Green Sahara hypothesis states that between 130 and 75 thousand years ago, the Sahara desert actually contained vast quantities of vegetation due to increased water availability in North Africa. This would have removed what is now a massive barrier to dispersion out of sub-Saharan Africa. However, some debate the extent of this 'Green Sahara,' stating that regions of North Africa may have remained arid, as evidenced by arid adapted species that have developed in this area for the past 7 million years.