Study of Human evolution

Human evolution and the various stages

1. STUDY OF HUMAN EVOLUTION NIRBHAY SUDHIR PIMPLE DEPARTMENT OF ZOOLOGY ABASAHEB GARWARE COLLEGE KARVE ROAD, PUNE-4.

2. Evolution  is change in the  heritable   characteristics  of biological  populations  over successive  generations .  These characteristics are the  expressions  of  genes  that are passed on from parent to offspring during  reproduction . Different characteristics tend to exist within any given population as a result of  mutation ,  genetic recombination  and other sources of  genetic variation .  Evolution occurs when evolutionary processes such as  natural selection  (including  sexual selection ) and  genetic drift  act on this variation, resulting in certain characteristics becoming more common or rare within a population.   What is evolution?

3. The  scientific theory  of evolution by natural selection was conceived independently by  Charles Darwin  and  Alfred Russel Wallace  in the mid-19th century and was set out in detail in Darwin's book  the Origin of Species . Human evolution  is the  evolutionary  process that led to the emergence of  anatomically modern humans , beginning with the  evolutionary history  of  primates —in particular  genus   Homo —and leading to the emergence of  Homo sapiens  as a distinct species of the  hominid  family, which includes the great apes. This process involved the gradual development of traits such as  human bipedalism  and  language .  As well as interbreeding with other  hominins , which indicate that human evolution was not linear but a web.

4. Australopithecus

5. Australopithecus , (Latin: “southern ape”) (genus  Australopithecus ), group of extinct  primates  closely related to, if not actually ancestors of, modern  human beings  and known from a series of  fossils  found at numerous sites in eastern, north-central, and southern  Africa . The various  species  of  Australopithecus  lived 4.4 million to 1.4 million years ago ( mya ), during the  Pliocene  and  Pleistocene  epochs (which lasted from 5.3 million to 11,700 years ago).   DESCRIPTION

6. As characterized by the fossil evidence, members of  Australopithecus   bore a combination of human like and ape like traits. They were similar to modern humans in that they were  bipedal  (that is, they walked on two legs), but, like  apes , they had small  brains . Their  canine teeth  were smaller than those found in apes, and their cheek  teeth  were larger than those of modern humans. The general term  australopith  (or  australopithecine ) is used informally to refer to members of the genus  Australopithecus . Australopithecines include the genus  Paranthropus  (2.3–1.2 mya ), which  comprises  three species of australopiths —collectively called the “ robusts ” because of their very large cheek teeth set in massive jaws. CHARECTERS

7. Homo erectus

8. Homo erectus , (Latin: “upright man”) extinct  species  of the  human  genus ( Homo ), perhaps an ancestor of modern  humans  ( Homo sapiens ).  H. erectus  most likely originated in  Africa , though Eurasia cannot be ruled out. Regardless of where it first evolved, the species seems to have dispersed quickly, starting about 1.9 million years ago ( mya ) near the middle of the  Pleistocene Epoch , moving through the African tropics,  Europe ,  South Asia , and  Southeast Asia DESCRIPTION

9. The first fossils attributed to  Homo erectus  were discovered by a Dutch army surgeon,  Eugène Dubois , who began his search for ancient human bones on the island of  Java  (now part of Indonesia) in 1890. Dubois found his first specimen in the same year, and in 1891 a well-preserved skullcap was unearthed at  Trinil  on the  Solo River . Considering its prominent browridges , retreating forehead, and angled rear skull, Dubois concluded that the Trinil cranium showed anatomic features intermediate between those of humans (as they were then understood) and those of  ap e s .  DESCRIPTION

10. This history has been recorded directly if imprecisely by many sites that have yielded  fossil  remains of  H. erectus . At other localities, broken  animal  bones and stone tools have indicated the presence of the species, though there are no traces of the people themselves.  H. erectus  was a human of medium stature that walked upright. The braincase was low, the forehead was receded, and the nose, jaws, and palate were wide. The  brain  was smaller and the  teeth  larger than in modern humans.  H. erectus  appears to have been the first human species to control  fire , some 1,000,000 years ago. The species seems to have flourished until some 200,000 years ago (200 kya ) or perhaps later before giving way to other humans including  Homo sapiens .

11. Several years later, near where the skull was discovered, he found a remarkably complete and modern-looking femur (thighbone). Since this bone was so similar to a modern human femur, Dubois decided that the individual to which it belonged must have walked erect. He adopted the name  Pithecanthropus  (coined earlier by the German zoologist  Ernst Haeckel ) and called his discoveries  Pithecanthropus erectus  (“upright ape-man”), but the  colloquial  term became “ Java man .” col *lo*qui* al adjective \ kə -ˈ lō-kwē-əl \:used in or characteristic of familiar and informal conversation; also : unacceptably informal: using conversational style

12. Neanderthal man

13. Neanderthal , ( Homo neanderthalensis , Homo sapiens neanderthalensis ), also spelled  Neandertal , member of a group of  archaic   humans  who emerged at least 200,000 years ago during the  Pleistocene Epoch  (about 2.6 million to 11,700 years ago) and were replaced or  assimilated  by early modern  human  populations ( Homo sapiens ) between 35,000 and perhaps 24,000 years ago. Neanderthals inhabited Eurasia from the Atlantic regions of Europe eastward to  Central Asia , from as far north as present-day DESCRIPTION

14. Belgium and as far south as the Mediterranean and southwest Asia. Similar archaic human populations lived at the same time in eastern Asia and in Africa. Because Neanderthals lived in a land of abundant  limestone   caves , which preserved  bones  well, and where there has been a long history of prehistoric research, they are better known than any other archaic human group. Consequently, they have become the archetypal “cavemen.” The name  Neanderthal  (or  Neandertal ) derives from the  Neander Valley (German  Neander Thal  or  Neander Tal ) in Germany, where the  fossils  were first found.

15. Although Neanderthals possessed much in common physically with early modern humans, the constellation of Neanderthal features is unique, with much variation among individuals as far as craniofacial (head and facial) characteristics are concerned. Features of the cranium and lower  jaw  that were present more often in Neanderthals than in early and recent modern humans include a low-vaulted cranium, large orbital and nasal openings, and prominent arched brow ridges. A pronounced occipital region (the rear and base of the skull) served to anchor the large neck musculature.

16. The cranial capacity of Neanderthals was similar to or larger than that of recent humans. The front teeth were larger than those in modern humans, but the molars and premolars were of a similar size. The lower jaw displayed a receding chin and was robustly built. The mental foramen, a small hole in the skull that allows nerves to reach the lower jaw, was placed farther back in Neanderthals than in recent humans, and a space between the last molar and the ascending edge of the lower jaw occurred in many individuals. There was also apparently less lumbar lordosis (back curvature) in Neanderthals

17. HOMO SAPIENS SAPIENS

18. Homo sapiens , (Latin: “wise man”) the  species  to which all modern  human beings  belong.  Homo sapiens  is one of several species grouped into the genus  Homo , but it is the only one that is not  extinct .  The name  Homo sapiens  was applied in 1758 by the father of modern biological classification   Carolus Linnaeus . Traditionally, this subspecies  designation  was used by paleontologists and anthropologists to separate modern human beings from more-archaic members of  Homo sapiens .  H. s. sapiens  is thought to have evolved sometime between 160,000 and 90,000 years ago in  Africa  before migrating first to the  Middle East  and  Europe  and later to  Asia ,  Australia , and the  Americas . DESCRIPTION

19. Currently,  H. s. sapiens  is the only widely accepted subspecies of  H. sapiens , and the necessity of this designation remains a matter of debate, since traditional taxonomic practice subdivides a  species  only when there is evidence of two or more distinct subgroups. Several subspecies of  H. sapiens  have been proposed. For example, Swedish naturalist and explorer  Carl Linnaeus , in the 10th edition of his  Systema Naturae  (1758), classified modern human beings into four subspecies according to geographic origin:  H. s. asiaticus ,  H. s. europaeus ,  H. s. afer , and  H. s. americanus . Linnaeus’s classification was later discarded because of the recognition of racial  prejudice  and outdated notions of European superiority  implicit  in his  taxonomy  and because of discoveries that only superficial differences existed between these groups

20. the earliest  Homo sapiens  had bodies with short, slender trunks and long limbs. These body proportions are an adaptation for surviving in tropical regions due to the greater proportion of skin surface available for cooling the body. More stocky builds gradually evolved when populations spread to cooler regions, as an adaptation that helped the body retain heat. Modern humans now have an average height of about 160 centimetres in females and 175 centimetres in males. Brain Homo sapiens  living today have an average brain size of about 1350 cubic centimetres which makes-up 2.2% of our body weight. Early  Homo sapiens , however, had slightly larger brains at nearly 1500 cubic centimetres .

21. Skull modern  Homo sapiens  skulls have a short base and a high braincase. Unlike other species of  Homo , the skull is broadest at the top. The fuller braincase also results in almost no post-orbital constriction or narrowing behind the eye sockets back of the skull is rounded and indicates a reduction in neck muscles face is reasonably small with a projecting nose bone brow ridge is limited and the forehead is tall orbits (eye sockets) are square rather than round Jaws and teeth jaws are short which result in an almost vertical face usually no gap ( retromolar space) between the last molar teeth and the jaw bone jaws are lightly built and have a protruding bony chin for added strength.  Homo sapiens  is the only species to have a protruding chin. shortened jaw has affected the arrangement of the teeth within the jaw. They are now arranged in a parabolic shape in which the side rows of teeth splay outwards rather than remain parallel as in our earliest long jawed ancestors. teeth are relatively small compared with earlier species. This is especially noticeable in the front incisor and canine teeth. front premolar teeth in the lower jaw have two equal-sized cusps (bumps on the chewing surface

22. THE HUMAN LINAGE