Transcript Slide 1
Hominid Evolution Physical changes in hominid characteristics and behavior over time. Homo Sapiens Sapiens (modern man, present day) http://www.bio.miami.edu/dana/pix/human_skull.jpg Homo Sapiens sapien (modern man, older, found in czech republic) http://www.bio.miami.edu/dana/pix/human_skull.jpg Homo Sapiens sapien (modern man, cro-magnon, oldest found in France) http://en.wikipedia.org/wiki/File:Cro-Magnon.jpg Homo sapiens rhodesiensis http://en.wikipedia.org/wiki/File:Broken_Hill_Skull_(Replica01).jpg Homo Sapiens neanderthalensis (Neandertal) http://en.wikipedia.org/wiki/File:Homo_sapiens_neanderthalensis.jpg Homo erectus pekinensis (peking man) http://en.wikipedia.org/wiki/File:Peking_Man_Skull_(replica)_presented_at_Pal eozoological_Museum_of_China.jpg Homo erectus modjokertensis Paranthropus (Australopithicus) boisei http://en.wikipedia.org/wiki/File:Australopithecus_boisei_P1060081.jpg Homo habilis (handy man) http://en.wikipedia.org/wiki/File:Homo_habilis-KNM_ER_1813.jpg Australopithicus africanus (taung child, Mrs. Ples) http://en.wikipedia.org/wiki/File:Taung%27s_child.jpg Sustralopithecus (Australopithicus) afarensis (lucy) http://www.skullsunlimited.com/graphics/bh-021t-lg.jpg Pan Troglodytes (Chimpanzee) http://www.boneclones.com/BC-003.htm Gorilla Gorilla (Gorilla) http://www.sideshowtoy.com/?page_id=4489&sku=BC001 General Trends in Hominid Evolution - Braincase • Smallest to largest: chimp, homo habilis, gorilla, a. africanus, S. afarensis, H erectus, neandertal, H.S. rhodesiensis, H. S. sapiens (cro-magnon to modern) • As hominids evolved, the braincase, in general got larger. General Trends in Hominid Evolution – Sagital Crest • Sagital crest was largest in the gorilla, chimp, A. boisei, and H. erectus. By the time modern man evolved the sagital crest had disappeared. • The sagital crest anchors extremely large jaw muscles and is found in animals that eat very tough food such as branches, shrubs, tough leaves, nuts, barks etc. General Trends in Hominid Evolution - Prognathism • In older species the prognathism sticks out farther, meaning a lesser angle. Chimp, gorilla, H. habilis, and S. afarensis show the smallest angle while H. sapiens sapiens has the steepest. • The greater the angle of prognathism, the weaker the jaw of the organism. This indicates that the diet of hominids got softer as the species evolved. General Trends in Hominid Evolution – other features • As species evolved, the foramen magnum moved from the back of the skull to the center. This indicates that the species went from walking on 4 legs to two over time. • As species evolved, the supraorbital ridge went from large to small. This structure provides reinforcement to the skull to account for the pressure of large jaw/facial muscles flexing. • The similar number of teeth and dental formula indicate that all members that we looked at evolved from a common ancestor. The diet did not change very much over time. Big Conclusions • Species that evolved at an earlier time had a harder diet than we do today. Older species ate nuts, bark, branches, and tough, woody stems. This is shown by larger sagital crest and supraorbital ridges, and lower prognathism angle. This indicates that early human ancestors lived in the forest and gradually migrated to open grasslands. Big Conclusions cont. • This move from forest to savannah also favors a more upright posture. In an environment with tall grasses walking on 2 legs allows you to see over the grass and look out for predators. • The large canines on the chimp and gorilla are not for eating meat but rather they are used for fighting and sexual selection. Large teeth are more attractive and indicate good genes.