Investigatory Project
Certificate of Authenticity
This is to certify that “K.SANTHOSH KUMAR” a student of class 12th has successfully completed the research product on the topic “HUMAN EVOLUTION”. Under the guidance of Mrs. KALPANADEVI (PGT BIOLOGY)
This project is absolutely genuine and does not indulge in plagiarism of any kind. This reference taken in making this project has been declared at the end of this project.
- Signature {Teacher In-Charge}
- Signature (Internal Examiner) Signature (External Examiner)
Acknowledgment
Having a successful investigatory project is really a great pleasure to us. It helps us improving a certain project and identifying new discoveries from raw materials which can be seen abundantly in our surroundings. So, we, the researchers would like to thank to the following persons who help us make this project successful. First, to our Teacher
Mrs.Kalpana Devi(PGT BIOLOGY) who gave us the wisdom, that lead us to come up on this great idea and for the guidance that made our project fruitful and helped us in the formulation of the study, and lastly, our parents who continuously support us in our financial needs in doing our project. Thank You!
Introduction
Human evolution is the evolutionary process leading up to the appearance of modern humans. While it began with the last common ancestor of all life, the topic usually covers only 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”). The study of human evolution involves many scientific disciplines, including physical anthropology, primatology, archaeology, linguistics, evolutionary psychology, embryology and genetics. History of study
Before Darwin
The word homo, the name of the biological genus to which humans belong, is Latin for “human”. It was chosen originally by Carolus Linnaeus in his classification system. The word “human” is from the Latin humanus, the adjectival form of homo. The Latin “homo” derives from the Indo-European root *dhghem, or “earth”. Linnaeus and other scientists of his time also considered the great apes to be the closest relatives of humans based on morphological and anatomical Similarities.
Darwin
The possibility of linking humans with earlier apes by descent became clear only after 1859 with the publication of Charles Darwin’s On the Origin of Species, in which he argued for the idea of the evolution of new species from earlier ones. 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”. The first debates about the nature of human evolution arose between Thomas Huxley and Richard Owen. Huxley argued for human evolution from apes by illustrating many of the similarities and differences between humans and apes, and did so particularly in his 1863 book Evidence as to Man’s Place in Nature. However, many of Darwin’s early supporters did not initially agree that the origin of the mental capacities and the moral sensibilities of humans could be explained by natural selection, though this later changed. First fossils
A major problem at that time was the lack of fossil intermediaries. Despite the 1891 discovery by Eugène Dubois of what is now called Homo erectus at Trinil, Java, it was only in the 1920 s 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 cave. 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.
The genetic revolution
The genetic revolution in studies of human evolution started when Vincent Sarich and Allan Wilson measured the strength of immunological cross-reactions of blood serum albumin between pairs of creatures, including humans and African apes (chimpanzees and gorillas). The strength of the reaction could be expressed numerically as an immunological distance, which was in turn proportional to the number of amino acid differences between homologous proteins in different species. By constructing a calibration curve of the ID of species’ pairs with known divergence times in the fossil record, the data could be used as a molecular clock to estimate the times of divergence of pairs with poorer or unknown fossil records. In their seminal 1967 paper in Science, Sarich and Wilson estimated the divergence time of humans and apes as four to five million years ago, at a
time when standard interpretations of the fossil record gave this divergence as at least 10 to as much as 30 million years. Subsequent fossil discoveries, notably Lucy, and reinterpretation of older fossil materials, notably Ramapithecus, showed the younger estimates to be correct and validated the albumin method. Application of the molecular clock principle revolutionized the study of molecular evolution.
Human Disperal
Anthropologists in the 1980s were divided regarding some details of reproductive barriers and migratory dispersals of theHomo genus. Subsequently, genetics has been used to investigate and resolve these issues. According to the Sahara pump theory evidence suggests that genus Homo have migrated out of Africa at least three times (e.g. Homo erectus, Homo hiedelbergensis and Homo sapiens), with other migrations occurring more recently (e.g. the Afro-asiatic language family into the Middle East). A broad study of African genetic diversity, headed by Sarah Tishkoff, found the San people had the greatest genetic diversity among the 113 distinct populations sampled, making them one of 14 “ancestral population clusters”. 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 haplogroups 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 evidence for archaic admixture in modern humans had been suggested by some studies.
Anatomical changes
Human evolution is characterized by a number of morphological, developmental, physiological, andbehavioral changes that have taken place since the split between the last common ancestor of humans and chimpanzees. The most significant of these adaptations are bipedalism, increased brain size, lengthened ontogeny (gestation and infancy), and decreased sexual dimorphism. The relationship between these changes is the subject of ongoing debate.Other significant morphological changes included the evolution of a power and precision grip, a change first occurring in H.
erectus.
Evidence
The evidence on which scientific accounts of human evolution is based comes from many fields of natural science. The main sources of knowledge about the evolutionary process has traditionally been the fossil record, but since the development of genetics beginning in the 1970s, DNA analysis has come to occupy a place of comparable importance. The studies of ontogeny, phylogenyand especially evolutionary developmental biology of both vertebrates and invertebrates offer considerable insight into the evolution of all life, including how humans evolved. The specific study of the origin and life of humans is anthropology, particularly paleoanthropology which focuses on the study of human prehistory.
Evidence from the fossil record
There is little fossil evidence for the divergence of the gorilla, chimpanzee and hominin lineages. The earliest fossils that have been proposed as members of the hominin lineage are Sahelanthropus tchadensis dating from 7 million years ago, Orrorin tugenensis dating from 5.7 million years agoand Ardipithecus kadabba dating to 5.6 million years ago. Each of these have been argued to be a bipedal ancestor of later hominins but, in each case, the claims have been contested. It is also possible that one or more of these species are ancestors of another branch of African apes, or that they represent a shared ancestor between hominins and other apes. The question of the relationship between these early fossil species and the hominin lineage is still to be resolved. From these early species, theaustralopithecines arose around 4 million years ago and diverged into robust (also called Paranthropus) and gracile branches, one of which (possibly A. garhi) probably went on to become ancestors of the genus Homo. The australopithecine species that is best represented in the fossil record isAustralopithecus afarensis with more than one hundred fossil individuals represented, found from Northern Ethiopia (such as the famous “Lucy”), to Kenya, and South Africa. Fossils of robust australopithecines such as A. robustus (or alternatively Paranthropus robustus) and A./P. boisei are particularly abundant in South Africa at sites such as Kromdraai and Swartkrans, and around Lake Turkana in Kenya.
The earliest members of the genus Homo are Homo habilis which evolved around 2.3 million years ago. Homo habilis is the first species for which we have positive evidence of the use of stone tools. As modern humans spread out from Africa, they encountered other hominins such as Homo neanderthalensis and the so-called Denisovans, who may have evolved from populations of Homo erectus that had left Africa around 2 million years ago. The nature of interaction between early humans and these sister species has been a long standing source of controversy, the question being whether humans replaced these earlier species or whether they were in fact similar enough to interbreed, in which case these earlier populations may have contributed genetic material to modern humans. This migration out of Africa is estimated to have begun about 70,000 years BP and modern humans subsequently spread globally, replacing earlier hominins either through competition or hybridization.
Bibilography
- WWW.GOOGLE.CO.IN
- WWW.en.wikipedia.org/wiki/Human_evolution
- WWW.GOOGLE.CO.IN/IMGHP
