Human evolution

Origin and phylogeny of Homo sapiens upto Australopithecus africanus.

1. Introduction to t he Human E volution Akum Paul Singh Roll No. 2084

2. Time of Origin of Man Primates started evolving in Eocene of tertiary period around 75-60 million years ago Evolution of man and ape started together from some tree-dwelling common ancestors about 25-30 million years ago Evolution of genus homo started about 5 million years ago

3. Place of origin of Man Man’s origin was probably in Asia, Africa and Europe More precisely man has originated in Central Asia because: Oldest known fossils have been obtained from China, Java and India Domesticated plants and animals is maximum in Asia No. of migrations of animals have occurred in the past from Asia Asian culture appears to be the oldest Climatic conditions in Africa, Asia and nearby places is most conductive for human evolution Rich fossil beds are discovered in Asia and Africa

4. Differences and Similarities between Man and Apes 1. Bipedal Locomotion Man Man walks on hindlimbs only Forelimbs and hands are freed for manupulatory and other functions Apes They walk on all the four arms Apes are still tree dwellers

5. 2. Upright Posture/ Musculo -skeleton Man Hindlimbs are longer than fore limbs Abdominal region is short and thorax became broad and flat Lumbar vertebrae are 4-5 in man (sacral vertebrae are fused) Lumbar curve is present Iliac bones of pelvic girdle are broad and expanded Tail is absent Skull is balanced straight on vertebral column Apes Forelimbs are longer than hind limbs Lumbar vertebrae are 6-7 in no. Lumbar curve is absent Skull is balanced at right angle to the vertebral column

6. 2. Face Man Orthognathous type Simian shelf absent Chin is present Eye brow ridges absent Occipital condyle and foramen magnum are directed downward Forehead is straight Canines small Apes Prognathous type Simian shelf is present Chin is absent Heavy ridges of bone project over the eyes Occipital condyle and foramen magnum are directed backward Forehead is slanting Canines large and protruding

7. 2. Teeth Man Dental arch is rounded parabola Canines not projecting Incisors are small Simian Gap is absent Apes Dental arch is straight sided U Canines are large and projecting forming tusks Incisors are large Simian gap( diastema ) is present in upper jaw between incisors and canines

8. 2. Brain and Cranial Cavity In man cranial cavity is more voluminous averaging 1350-2000cc or even more whereas in apes it is 450-600 cc 3.Food Man is omnivorous whereas apes are herbivorous 4.Binocular vision Man has large forwardly directed eyes giving stereoscopic vision Rod and Cone cells are present in retina 5.Olfactory lobes less developed in man as compared to apes 6.Hearing capacity less in man 7. Breeding capacity low in humans than apes

9. Early Human Fossils Orrorin tugenensis Early species of  Hominids, estimated at 6.1 to 5.7 million years First fossil discovered in 2000  from  Tugen Hills in  Kenya The 20 specimens found as of 2007 include: the posterior part of a mandible in two pieces; a symphysis and several isolated teeth; three fragments of  femora; a partial  humerus ; a proximal phalanx; and a distal thumb phalanx. 

10. Features of Orrorin Orrorin  had small teeth relative to its body size H ead  is spherical and rotated anteriorly Neck  is elongated and oval in section L esser trochanter protrudes medially. While this suggests that   Orrorin  was bipedal, the rest of the  postcranium  indicates it climbed trees P roximal phalanx is curved, the distal  pollical phalanx is of human proportions Orrorin  lived in dry evergreen forest environment, not the  savanna h

11. How Orrorin is related to Human evolution? Still not confirmed; debates going on  Its discovery was an argument against the hypothesis that Australopithecines  are human ancestors If  Orrorin  proves to be a direct human ancestor, then  Australopithecines  such as  Australopithecus afarensis  ("Lucy") may be considered a side branch of the hominid family tree Orrorin  is both earlier, by almost 3 million years, and more similar to modern humans than is  A. afarensis . The main similarity is that the Orrorin femur is morphologically closer to that of  H. sapiens  than is  Lucy's ; there is, however, some debate over this point.

12. Sahelanthropus tchadensis The fossils were discovered in the  Djurab Desert of Chad Found between July 2001 to March 2002 Existing fossils include a relatively small cranium known as  Toumaï , fine pieces of jaw, and some teeth

13. Features The braincase, being only 320 cm³ to 380 cm³ in volume, is similar to that of extant chimpanzees  Cranial features show a flatter face, u-shaped dental arcade, small canines, an anterior foramen magnum, and heavy brow ridges Because no postcranial remains (i.e., bones below the skull) have been discovered, it is not known definitively whether  Sahelanthropus tchadensis   was bipedal or not

14. Relation with humans and Chimpanzees   If Toumaï is a direct human ancestor, then its facial features bring into doubt the status of Australopithecus  because its thickened brow ridges were reported to be similar to those of some later fossil hominids (notably  Homo erectus ), whereas this morphology differs from that observed in all australopithecines, most fossil hominids and extant humans . Sahelanthropus  may represent a common ancestor of humans and chimpanzees Another possibility is that Toumaï is related to both humans and chimpanzees, but is the ancestor of neither.  the discoverers suggested that the features of  S. tchadensis  are consistent with a female proto-gorilla. 

15. Ardipithecus Ardipithecus  is a genus of an extinct hominine that lived during Late Miocene and Early Pliocene in Afar Depression,  Ethiopia O ne of the earliest ancestors of humans after they diverged from the main ape lineage  Two fossil species are described in the literature : A. ramidus , which lived about 4.4 million years ago A . kadabba , dated to approximately 5.6 million years ago   Behavioral analysis showed that  Ardipithecus  could be very similar to those of chimpanzees, indicating that the early human ancestors were very much like chimpanzees in behaviour

16. Autralopithecus (The first ape man) First fossil was an unusual skull cap of a child from a Pleistocene lime quarry near village of Taung in South Africa Discovered by Raymond A. Dart in 1924 Australo-pithecus means Southern-Ape These were fully bipedal hominids with relatively small brain Lived from 4 to 15 million years ago

17. Characteristics Short statured measuring 4-5 ft Walked nearly or completely straight on two hind legs Lived in open and had given up arboreal life Vertebral column have distinct lumbar curve Thighs and hips well adapted for standing, walking and running Pelvics broad and flattened

18. Characteristics Big toes in feet were still adapted for grasping Arms adapted for brachiation Brain was small but more or less man-like in shape Cranial cavity 450-600cc Protruding jaws with larger teeth Dental arch was smoothly rounded parabola Simian gap between canines and premolars Face was prognathous and chin absent Eyebrow ridges projecred over eyes

19. A.africanus 1.Also called gracile forms 2. 1.2 m tall 3.Weighed 25-30 kg 4.Molars larger and stronger 5. Chew food by grinding motion 6. Were omnivorous A.Robustus 1.Also called robust forms 2. 1.5 m tall 3.Weighed almost twice the gracile form 4.Massive molars 5 . Chew food by grinding motion 6 . Were herb ivorous Two distinct species of Australopithecus have been identified:

20. Lucy Also knonw as  AL 288-1 discovered in 1974 at  Hadar  in the Awash Valley of the Afar Triangle in   Ethiopia several hundred pieces of bone representing about 40% of the skeleton of a female Australopithecus afarensis   Lucy is estimated to have lived 3.2 million years ago The skeleton shows evidence of small skull capacity akin to that of apes and of bipedal upright walk akin to that of humans, supporting the debated view that bipedalism preceded increase in brain size in human evolution