Evolution from apes to humans, s. mubasher

Evolution from apes to humans, s. mubasher

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  Dr. Mubasher’s Blog DEPARTMENT OF BIOLOGY OXFORD HIGH SCHOOL T. M. KHAN November 20, 2012 The Evolution From Apes to Humans Posted by Dr. Solangi Mubasher, D.V.M Inside the story  What is human evolution?  If apes 'turned into' humans, then apes should no longer exist?  Is there any role of tools in evolution?  Is there any role of environment in evolution?  Scientific disciplines involved in evolution, including, Taxonomical, physical, anatomical, anthropological, archaeological and genetical aspects. Introduction The humans and apes evolved from a common ancestor. That makes humans and apes related species. The molecular evidence showed very clearly that chimpanzees are our closest living relatives, and so, logically, we must share an ancestor in common at some point in the past. This common ancestor, wasn’t necessarily identical to modern chimpanzees- remember, all populations are in a state of evolutionary flux, it’s just that some are required by their environments to evolve faster than others. Either way, we need to understand that the phrase “Humans evolved from apes” has two distinct meanings for people who hear it. One emphasizes the word “apes” and the other emphasizes the word “from.” By one way of thinking, the phrase means “Homo sapiens is one of several species of ape.” By the other way of thinking, the phrase means “Homo sapiens evolved from apes into something different.” Either way, some people will be annoyed. Either way, the statement may be correct. After diverging with the other great apes, bipedalism evolved in the Australopithecines, but they weren’t human quite yet. Once a large enough brain evolved, rudimentary tools began to be used, as seen in Homo habilis, the Handyman. These then became migratory hunter/gatherers, as seen in Homo erectus. Modern humans evolved the use of language, and migrated out of Africa and all over the world, to where we are today.
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  Evolution from apesto humans by Dr. S. Mubasher, D.V.M Evolution from apes to humans Geology teaches that the earth was lifeless in the beginning, when where and why was life started, no one knows about that. Many people have been willing to admit that evolution may occur in plants and animals, but they refuse to concede that it occurs in man. Indeed, some have been unwilling to consider man an animal. As far as man's evolution is concerned, there is abundant evidence from embryology, comparative anatomy, and other fields to illustrate 2 his emergence from other forms (a common ancestor of apes and humans). No evolutionist maintains that man sprang from any of our present day apes and monkeys. On the contrary, it is thought that millions of years ago there was an apelike group of animals which gave rise to two branches. The first branch included the arboreal apes, and the second was a terrestrial group, the man animals. By the process of evolution man emerged from this apelike stock as a "new creation." According to the evolutionists the first ape like group of animals served as ancestors to humans and apes, this statement is based upon the findings, fossils of present day humans with slight variations or related ones. Eventually it is not clear that first group of animals were alike to present humans or apes. However, it is hard to trace early human history, for there have been comparatively few finds. Asia, often called the "cradle of the race," and Africa have been little explored. As we consider this very brief outline of the story of early man, we must remember that the conclusions are based on observations not of complete specimens, but rather of fragmentary, fossil, skeletal remains. Knowledge of present day savages, comparison of the skeletons of man with those of the present-day great apes, as well as a study of the life of these living animals and the biology of modern man all afford evidence of the origin and evolution of modern man. According to the earlier taxonomists that have a better look on evolutionary aspects of classification there are three major groups of organisms that share a single ancestor.  The New World monkeys, living on the American continents  The Old World primates, including monkeys and apes throughout Africa and Europe  The various species of monkeys that lived in Asia, but those are all extinct for various reasons Note that all humans belong to that second group, only because primates include old age animals, and those may be considered as ancestor to human and apes, wherever they might have migrated since. Later, the ape lineage itself split into two groups  The "lesser ape", the current descendants of which are called gibbons  The "great ape", which includes all other apes like gorillas, chimps and humans. The closest living relatives to humans living today are the chimps, of which there are two species: Pan Troglodytes (the common chimp) and Pan Paniscus (the bonobo chimp). Human evolution is characterized by a number of morphological, developmental, physiological, and behavioral changes that have taken place since the split between the last common ancestor of humans and chimpanzees. The most significant of these adaptations are 1. Bimetallism 2. Increased brain size 3. Lengthened ontogeny (gestation and infancy) 4. Decreased sexual dimorphism
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  Evolution from apesto humans by Dr. S. Mubasher, D.V.M Other physiological changes that have also characterized the process of evolution are increased importance on vision rather than smell; a smaller gut; loss of body hair; evolution of sweat glands; a change in the shape of the dental arcade from being u-shaped to being parabolic; development of a chin (only found in Homo sapiens), development of styled; development of a descended larynx. Natural selection and environment also played an important role in evolution. Natural selection is variations in genetic variety that changes a species within itself. For instance, say a tribe of fair skinned people 3 traveled to a very hot climate, those people with darker skin would be more likely to survive thereby passing on their dark skinned genes and eventually weeding out the fair skinned people. Evolution only occurs when it is necessary. Some apes evolved into man because either they moved to a new environment or their existing environment changed, making evolution necessary for survival. So, the apes who needed to adapt to their new environment through evolution to survive either did so or were wiped out (apparently, they changed, creating the human race), or stayed in a friendly environment, making evolution unnecessary and therefore, nonexistent (the apes in these conditions remained apes). As Lamarck (1744-1820) pointed out that “animals and plants vary with changing environmental conditions and that, as they adjust themselves to new conditions, they apparently change their form…. Organs used tend to develop and those not used tend to atrophy (Perry D. Straus bough, General Biology, 2nd ed. 1947, p.623)”. Homo Homo sapiens are the only extant species of Homo genus. While some other, extinct Homo species might have been ancestors of Homo sapiens, many were likely our "cousins", having speculated away from our ancestral line. Zoological classification showing Extant hominoids: humans (genus Homo), chimpanzees and bonobos (genus Pan), gorillas (genus Gorilla), orangutans (genus Pongo), and gibbons (four genera of the family Hylobatidae: Hylobates, Hoolock,Nomascus, and Symphalangus). All except gibbons are hominids. The topic of evolution from apes to Humans usually only covers the evolutionary history of primates, in particular the genus Homo, and the emergence of Homo sapiens as a distinct species of hominids (or "great apes"), and according to it The humans and apes evolved from a common ancestor (which may either alike to humans or apes). Species close to the last common ancestor of gorillas, chimpanzees and humans may be represented by Nakalipithecus fossils found in Kenya and Ouranopithecus found in Greece.
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  Evolution from apesto humans by Dr. S. Mubasher, D.V.M Molecular evidence suggests that between 8 and 4 million years ago, first the gorillas, and then the chimpanzees (genus Pan) split off from the line leading to the humans; According to the human evolutionary genetics human DNA is approximately 98.4% identical to that of chimpanzees when comparing single nucleotide polymorphisms. But the fossil record of gorillas and chimpanzees is limited due to both poor preservation and sampling bias. The earliest documented members of the genus Homo are Homo habilis which evolved around 2.3 million years ago. Homo habilis is the first species for which 4 we have positive evidence of use of stone tools. The diagram below shows the great apes. The brains of these early hominines were about the same size as that of a chimpanzee. During the next million years a process of encephalization began, and with the arrival of Homo erectus in the fossil record, cranial capacity had doubled to 850cc. Homo erectus and Homo ergaster were the first of the hominine to leave Africa, and these species spread through Africa, Asia, and Europe (1.3 to 1.8 million years ago) In the eye of History Although the work upon evolution was started first by the Greek philosophers by giving a concept of derivation of higher organisms from lower ones (Arthur W. Haupt, Fundamentals of Biology, 3rd ed. 1940, p.389). There are three major theories concern to the evolution. No one theory is entirely adequate each has its strong and weak points. Thus the method by which evolutionary changes have come about is still imperfectly understood. 1. French naturalist, Jean Baptiste de Lamarck (1477-1829), the theory was based upon inheritance and acquired characters, 1801. 2. English naturalist, Charles Darwin (1809-1882), the theory was based upon natural selection 3. Dutch botanist Hugo de Vries, The theory mutation, 1901 Some other experts also talked about the topic.
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  Evolution from apesto humans by Dr. S. Mubasher, D.V.M 5 Linnaeus assigned the humans and apes to a single taxonomic order. He stated nothing about ape to human evolution, but his categorization of humans with the apes certainly encouraged later naturalists to think of the two as related by descent.” (Order Primates,10th ed., 1758). The voyages of discovery had revealed the existence of chimpanzees, orangutans, and gibbons (the gorilla remained unknown to European science until the 1840s, and the bonobo, until the 1920s). For the most part, taxonomic classifications prepared by Linnaeus' successors kept Homo separate from the apes. By 1800 this was the norm. But even those classifiers who failed to follow Linnaeus' classification and placed humans and non-human primates in separate orders (Order Bimanes and Order Quadrumanes, respectively) generally recognized an affinity between apes and human beings. For example, Comte de Buffon stated that an ape "is only an animal, but a very singular animal, which a man cannot view without returning to himself." (Histoire naturelle, vol.14, p.4, 1766). Philosophe Delisle de Sales commented that “the apes seem to form an intermediate line between animals and human beings." (Histoire philosophique du monde primitive, 1794). The French naturalist Constant Duméril speaks about the genus Pithecus as containing "the species of apes that most closely approach man (Zoologie analytique, 1806, p. 8)." Similarly, in his systematic arrangement of the animal kingdom Cuvier follows the separate arrangement, but describes Quadrumanes as "the order closest to man (Règne Animale, p. 79).” Jean Baptiste de Lamarck (1744-1829) The idea of ape to human evolution found its original spark in the 18th century when Jean-Baptiste Lamarck the first naturalist with the nerve to propose publicly and explicitly that; human beings had evolved from apes. He said “Certainly, if some race of apes, especially the most perfect among them, lost, by necessity of circumstances, or some other cause, the habit of climbing trees and grasping branches with the feet, and if the individuals of that race, over generations, were forced to use their feet only for walking and ceased to use their hands as feet, doubtless these apes would be transformed into two-handed beings and their feet would no longer serve any purpose other than to walk (Philosophie zoologique, 1809).” Robert Chambers stated that “the primates are distinguished by greater relative magnitude of brain, by agility, and by the use of the hand. The
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  Evolution from apesto humans by Dr. S. Mubasher, D.V.M signal superiority of the human species is thus prepared for and betokened in the immediately preceding portions of the line: it might have been seen, ere man existed, that a remarkable creature was coming upon the earth (Vestiges of the Natural History of Creation (1844).” Darwin and evolution Charles Darwin is considered to be the presenter of the modern theory of 6 organic evolution. He has a scientific background for environment as well as heredity as his father and grandfather were physicians and maternal grandfather was a pot maker. The possibility of linking humans with earlier apes by descent only became clear after 1859 with the publication of Charles Darwin's book the “Origin of Species”. However some other scientists and researchers also commented on same topic but no one clearly declared anything about human evolution as much clear as the Darwin. Although Darwin's book did not address the question of human evolution, saying only that "Light will be thrown on the origin of man and his history", but 25 years research on evolution published in this book has had a more profound influence on human thought than any other scientific work ever written. It was this book that resulted in the establishment of the principle of evolution as a fundamental scientific generalization. The first debates about the nature of human evolution arose between Thomas Huxley and Richard Owen. Huxley Darwin's friend and advocate Thomas Henry Huxley was far bolder on this topic than was Darwin himself, he argued for human evolution from apes by illustrating many of the similarities and differences between humans and apes, and did so particularly in his book Huxley, Evidence as to Man's Place in Nature, 1863. Huxley summarized the many anatomical traits shared by humans and apes and asserted that such evidence supported the hypothesis that humans and apes had evolved from a recent common ancestor. It was the first book devoted expressly to the topic of human evolution. However, many of Darwin's early supporters (such as Alfred Russell Wallace and Charles Lyell) did not agree that the origin of the mental capacities and the moral sensibilities of humans could be explained by natural selection. Darwin published nothing on the topic until 1871, when his own book “The Descent of Man, 1871” appeared. Darwin applied the theory of evolution and sexual selection to humans. He not only discuss the topic but give firm bases of evolution and suggest that how the evolution takes place, his theory is based upon variation, heredity and natural selection or survival to the fittest. It has been suggested that the factor of isolation must be added to that of natural selection for the effective creation of new species. As everyone knows that if dog is compared to wolf and cat than it is more alike to the wolf than cat, but dog is more alike to cat if it is compared to the horse. Eventually dog, cat and wolf are canines where as horse is herbivore. Thus more is the resemblance of two organisms shows their closer relationship. First fossil A major problem of the entire process of evolution was the lack of fossil intermediaries, despite the 1891 discovery by Eugène Dubois of what is now called Homo erectus. It was only in the 1920s when such fossils were discovered in Africa, that intermediate species began to accumulate. In 1925 Raymond Dart described Australopithecus africanus. The type specimen was the Taung child, an Australopithecine infant which was discovered in a
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  Evolution from apesto humans by Dr. S. Mubasher, D.V.M cave. The child's remains were a remarkably well-preserved tiny skull and an endo cranial cast of the brain. Although the brain was small (410 cm³), its shape was rounded, unlike that of chimpanzees and gorillas, and more like a modern human brain. Also, the specimen showed short canine teeth, and the position of the foramen magnum was evidence of bipedal locomotion. All of these traits convinced Dart that the Taung baby was a bipedal human ancestor, a transitional form between apes and humans. 7 Steps of evolution A bipedal step, to be precise- the first thing to distinguish our ancestors from chimpanzee ancestors is the ability to walk upright. But being able to walk upright doesn’t earn the scientific, phylogenetic designation of human. Australopithecus, (~3 to 2 m. years), South Africa We designate all human species by the genus “Homo” as in our binomial, “Homo sapiens.” But these first human ancestors weren’t human enough to be considered part of our genus, and instead are called, “Australopithecus.” One species of this genus in particular is thought to have been ancestral to humans- Australopithecus afarensis, one specimen of which has been nicknamed, “Lucy.” Like most of the Australopithecines, Lucy lived in Africa. Lucy, and the rest of her species, resembled chimpanzees in a lot of ways, but one difference is obvious- she walked upright, like a human. And not just sometimes, the bone structure of her pelvis indicates that she was upright most of the time. The expansion of the brain was the next big change in human evolution. This was different than a lot of scientists had expected- they had assumed that a larger brain would have been the first change in the human-chimpanzee divergence, followed by other human traits such as bipedalism and tool use.
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  Evolution from apesto humans by Dr. S. Mubasher, D.V.M Homo habilis, (~2.5 to 1.5 m. years), Africa The first human, or at least the first recognizable human species to which we’re willing to give the designation, is the Handyman, Homo habilis. The Handyman lived between 1.5 and 2.5 million years ago, and he gets his name 8 because rudimentary tools have been found with fossils of this species. These tools weren’t anything spectacular- just flakes of stone used as rudimentary knives, for the cutting of meat off dead animals. It’s unlikely that the Handyman was a hunter- more likely, he would have taken meat from already dead animals like a scavenger. Homo erectus, (~2 to 0.4 m. years), Africa, China Homo erectus just next to the Homo habilis; is the major step in human evolution. Homo erectus or the Upright Man arose in Africa about 1.5 to 1.8 million years ago. Homo erectus had a larger brain than Homo habilis, and its anatomy was more similar to modern humans. But the most interesting thing about Homo erectus was its incredible success- it was the first human species to engage in actual hunting, and this had the effect of expanding its territory. There is also evidence that Homo erectus was able to control fire. Homo sapiens (0.2 m. years, present) Homo erectus is the last major evolutionary transition before we get to modern humans, Homo sapiens. Homo floresiensis (~0.09 to 0.013 m. years), Indonesia In 2003 a skeleton was found, believed to be a woman of about 30 years of age. It has been dated to approximately 18,000 years old, one meter in height, with a brain volume of just 380 cm3 (considered small for a chimpanzee and less than a third of the H. sapiens average of 1400 cm3). Homo floresiensis (hobbit) has been named for its small size, possibly shared a common ancestor with modern humans, but split from the modern human lineage and followed a distinct evolutionary path. However, there is an ongoing debate over whether H. floresiensis is indeed a separate species. Some scientists hold that H. floresiensis was a modern H. sapiens with pathological dwarfism, an also it was found with tools only associated with H. sapiens. The hypothesis of pathological dwarfism, however, fails to explain additional anatomical features like form of bones in the wrist, forearm, shoulder, knees, and feet that are unlike those of modern humans (diseased or not) but much like those of ancient members of our genus. Additionally, this hypothesis fails to explain the
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  Evolution from apesto humans by Dr. S. Mubasher, D.V.M find of multiple examples of individuals with these same characteristics, indicating they were common to a large population, and not limited to one individual. Geographic distribution of evolution In 2007, Japanese scientists believe they found the jawbone and teeth of just such an animal. By studying the size and shape of the teeth, they determined 9 that the ape was gorilla-sized and had an appetite for hard nuts and seeds. They named it Nakalipithecus nakayamai and calculated its age to be 10 million years old. That puts the ape in the right place on the time line. More important, the scientists found the ancient bones in the Samburu Hills of northern Kenya. That puts N. nakayamai in the right geographic place, along a trajectory of hominid evolution that stretches for several hundred miles in eastern Africa. The Middle Awash region of Ethiopia lies to the north, where the African continent dead-ends into the Red Sea. In this theory, there was a coastal dispersal of modern humans from the Horn of Africa around 70,000 years ago. This group helped to populate Southeast Asia and Oceania, explaining the discovery of early human sites in these areas much earlier than those in the Levant. A second wave of humans dispersed across the Sinai Peninsula into Asia, resulting in the bulk of human population for Eurasia. This second group possessed a more sophisticated tool technology and was less dependent on coastal food sources than the original group. Much of the evidence for the first group's expansion would have been destroyed by the rising sea levels at the end of each glacial maximum. Richard Dawkins has come out in support of an “Out of Africa again and again” hypothesis, which suggests that Homo sapiens migrated out of and back into Africa several times before finally spreading out over all the continents. This hypothesis is backed up by genetic evidence tracing the genetic similarity of various genes among different human populations, and it looks the most promising. One of the major differences setting Homo sapiens aside from the other hominids is our use of language. This development is likely what allowed modern human society to expand and become as complex as it is now. Because diet of Homo erectus became more reliant on animals than plants, it began to migrate, and thus spread out of Africa, and colonized south East Asia, even going up farther north into Eurasia. Anatomic evidences of evolution We classify human species- that is, species that belong to the genus “Homo” not only on the basis of walking upright and pelvis but also to the vertebral column, feet and ankles, and skull the expanding brain followed soon after. Perhaps the most significant changes are in the pelvic region, where the long downwards facing iliac blade was shortened and became wide as a requirement for keeping the center of gravity stable while walking. The shortening and narrowing of the pelvis evolved as a requirement for bipedalism and had significant effects on the process of human birth which is much more difficult in modern humans than in other primates. The femur evolved into a slightly more angular position to move the center of gravity towards the geometric center of the body. The knee and ankle joints became increasingly robust to better support increased weight. Also in order to support the increased weight on each vertebra in the upright position the human vertebral column became S-shaped
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  Evolution from apesto humans by Dr. S. Mubasher, D.V.M and the lumbar vertebrae became shorter and wider. In the feet the big toe moved into alignment with the other toes to help in forward locomotion. The arms and forearms shortened relative to the legs making it easier to run bipedal. Genetic evidences of evolution Anthropologists in the 1980s were divided regarding some details of 10 reproductive barriers and migratory dispersals of the Homo genus. Subsequently, genetics has been used to investigate and resolve these issues. Progress in DNA sequencing, specifically mitochondrial DNA (mtDNA) and then Y-chromosome DNA advanced the understanding of human origins. Sequencing mtDNA and Y-DNA sampled from a wide range of indigenous populations revealed ancestral information relating to both male and female genetic heritage. Aligned in genetic tree differences were interpreted as supportive of a recent single origin. Analyses have shown a greater diversity of DNA patterns throughout Africa. The research also located the origin of modern human migration in south-western Africa, near the coastal border of Namibia and Angola. The fossil evidence was insufficient for Richard Leakey to resolve this debate. Studies of in Y-chromosomal DNA and mitochondrial DNA have largely supported a recent African origin. Evidence from autosomal DNA also predominantly supports a Recent African origin. However, new evidence has just been made available that shows by examining the human and chimpanzee genomes that human and chimpanzee ancestors diverged and then converged, before diverging for a final time less than 5 million years ago. Genetic analysis suggests that humans and chimpanzees evolved into separate species which then interbred, forming a hybrid species which then bred back into one of the parent populations. It’s not clear whether this human- chimpanzee hybrid returned to the human or the chimpanzee population, but the molecular evidence is clear that the hybridization did happen- the X chromosome has a particularly recent connection to the chimpanzee genome. This means that human-chimpanzee hybrid males would have been infertile, but the females were not. Thus the characters returned back to the parental population, mixing chimpanzee and human genes each time. But regardless of the human-chimpanzee hybrids, eventually the two lines did split for good. And gradually, our ancestors changed from being something that was willing to mate with a chimpanzee, into something that would rather hunt them for food, train them for entertainment, or sequence their DNA. What was the first step? The first step, as it seems, is literally a step. A bipedal step, to be precise- the first thing to distinguish our ancestors from chimpanzee ancestors is the ability to walk upright. Some common questions If apes 'turned into' humans, then apes should no longer exist? Although there are several ways to attack this assertion, the bottom line rebuttal is simple; the humans didn't descend from apes. That's not to say humans and apes aren't related, but the relationship can't be traced backward along a direct line of descent, one form morphing into another. It must be traced along two independent lines, far back into time until the two lines merge. The intersection of the two lines represents something special, what biologists refer to as a common ancestor. This apelike ancestor, which probably
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  Evolution from apesto humans by Dr. S. Mubasher, D.V.M lived 5 to 11 million years ago in Africa, gave rise to two distinct lineages, one resulting in hominids (humanlike species) and the other resulting in the great ape species living today. Or, to use a family tree analogy, the common ancestor occupied a trunk, which then divided into two branches. Hominids developed along one branch, while the great ape species developed along another branch. Is there any role of tools in evolution? The brain of a modern human consumes about 20 watts (400 kilocalories per 11 day), a fifth of body's total energy consumption. Increased tool use would allow hunting for energy-rich meat products, and would enable processing more energy-rich plant products. Researchers have suggested that early hominids were thus under evolutionary pressure to increase their capacity to create and use tools. Is there any role of environment in evolution? Evolution only occurs when it is necessary. Some apes evolved into man because either they moved to a new environment or their existing environment changed, making evolution necessary for survival. So, the apes who needed to adapt to their new environment through evolution to survive either did so or were wiped out (apparently, they changed, creating the human race), or stayed in a friendly environment, making evolution unnecessary and therefore, nonexistent (the apes in these conditions remained apes). Study suggested: th 1. Charles Darwin, The origin of Species by means of natural Selection, 6 ed. st 2. Joseph II, Homo Sapience, 1 ed. 2009 nd 3. Perry D. Straus bough and Bernal R. Weimer, General Biology, 2 ed. 1947 rd 4. Arthur W. Haupt, Fundamentals of Biology, 3 ed. 1940 5. Are humans really descended from apes? by William Harris 6. Falsehood: Humans evolved from apes by Greg Laden, June 25, 2010 7. If people evolved from apes why are there still apes? Land Mammals Questions, Answers.com 8. Out of Africa again and again by Richard Dawkins 9. Microevolution.net 10. Sinobiological.com 11. Wikipedia.com For queries and kind suggestions drmubasher.webnode.com [email protected]