• Hominin Evolution - Classification
Hominin Evolution - Classification •Aims: •Must be able to outline the characteristics used for classification of Hominins. •Should be able to outline the main differences between species for the main characteristics. •Could be able to apply knowledge of characteristics to group organisms. Hominin Evolution - Classification Human evolution is the physical and cultural development and change of our hominin ancestors to modern humans. Humans are Mammals: Humans are Primates: Primate Grades Homo sapiens = One of approximately 200 living primate species, which together constitute the order Primates. Homo sapiens have inherited a set of anatomical and behavioral features that reflect our evolutionary history. By studying the characteristics of present-day primates, we are able to look back at stages in our own evolutionary development. Prosimians New World Monkeys Old World Monkeys Apes Hominids Primate Characteristics • Combination of features that are unique to their group. • Anatomy is well adapted to an arboreal (tree-dwelling) lifestyle. • They possess: • Superior intelligence • Often complex social behavior • A highly developed problem solving ability Primate Physical Features • Features that distinguish primate species from each other include: • Tail anatomy • Skull anatomy, including: Brow ridges Vision Nostrils Snout and lips • Limb length • Hand and foot anatomy Primate Skulls • The skulls of various primate groups: • Ruffed Lemur Tarsier Spider monkey Chacma Baboon Borneo Orangutan Chimpanzee Some primates have a heavy brow ridge while others have little or no apparent brow ridge. Gorilla Skulls • • Gorillas exhibit sexual dimorphism in skull features. Female gorilla skulls differ from those of males by having: Very small sagittal crest Small nuchal crest Large sagittal crest Female skull smaller than male Large nuchal crest Female Male Gorilla Skull Features Sagittal crest (attachment site for jaw muscles) Low, small cranial vault Brow ridge Nuchal crest (for the attachment of neck muscles) Heavy malar (cheek bone) Massive zygomatic arch through which jaw muscles pass Diastema (gap) Protruding muzzle Foramen magnum positioned at rear Large incisors Massive jaw with no chin Large molars for grinding vegetation Large canines used as defensive weapons Primate Tails • Features that distinguish primate tails: • Tails present or absent • A prehensile tail can be used to grip things • Furred or not furred • Long or short Primate Feet and Hands • Hands and feet of various primate groups: Hand Hand Tarsier Loris Foot Hand Foot Foot Squirrel Monkey Hand Baboon Hand Orangutan Foot Hand Foot Gibbon Foot Foot Hand Gorilla Hand Chimpanzee Foot Primate Feet and Hands • Hands and feet of various primate groups can be distinguished by the following features: • The presence of claws or nails • Thumbs or big toes opposable or non-opposable Human hand Human foot Opposable thumb Non-opposable big toe Tarsier foot Claws on some fingers Gorilla foot Nails Opposable big toe Primate Limbs • An important feature that distinguishes certain primates is limb length - the ratio of the length of arms to legs Arms longer than the legs Legs longer than the arms Primate Classification – Based on Physical Characteristics Order Suborder Infraorder Superfamily Family Subfamily Tribe Plesiadapiformes (archaic primates) Lemuriformes Prosimii (prosimians) Lorisiformes P R I M A T E S Tarsiiformes Platyrrhini (New World simians) Anthropoidea (simians or anthro poids) extinct plesiadapiformes (Purgatorius) Lemuroidea Lemuridae Indriidae lemur indri Adapoidea Adapidae extinct adapiformes Lorisoidea Lorisdae loris, galago (bush baby) Tarsiidae tarsier Omomyid ae extinct omomyiformes Callitrichid ae marmoset, tamarin Cebidae (true mon keys) cebus monkey, spider monkey, howler monkey, capuchins, owl monkey, sakis Cercopith ecid ae colobus, langurs, macaque, baboon Tarsioidea Ceboidea (New World Monkeys) Cercopithecoide a (Old World Monkeys) Catarrhini (Old World Simians) Examples Oreopitheci dae Hominoidea (apes and humans) Human classification extinct Oreopithecus Hylobatid ae gibbon, siamang Pongidae Hominida e Homininae Extinct lineage orangutan, Gorillini gorillas Panini chimpanzees Hominini humans Hominid or Hominin? Hominid – Group consisting of all modern and extinct Great Apes (Modern human beings, chimpanzees, gorillas and orang-utans and all immediate ancestors). Hominin – Group consisting of modern humans, extinct human species and all of our immediate ancestors. Classifications Can Change… Modern humans, extinct human species and all immediate ancestors. •Pre 1980 hominid had the same meaning that hominin now has… •Hominid has now been designated a broader meaning (including Great Apes and their ancestors). •Many texts and websites still use the old naming system – beware! Why Change? •Over time biological classification changed due to improved techniques and better knowledge about the biology and the evolutionary relationships of different living things: •E.g. DNA analysis Genetic Similarity of Primates • The genetic relationships among the primates have been investigated using DNA hybridization as well as comparing DNA sequences. DNA Similarity (%) to Humans Genetic Similarity of Primates • Human DNA was compared with that of the other primates and largely confirmed what was suspected from anatomical evidence. Patterns of relationship among the apes and Old World monkeys based on information from DNA-DNA hybridization: Human Pygmy chimpanzee Common chimpanzee Gorilla Orangutan Gibbons Old World monkeys Primate Evolution Lemurs & lorises Present Tarsiers New World monkeys Old World monkeys Gibbons Orangutans Gorillas Chimpanzees Humans PLEISTOCENE 1.8 PLIOCENE Gigantopithecus 5 O. tugenensis S. tchadensis Ouranopithecus 10 Sivapithecus Krishnapithecus Kenyapithecus Dryopithecus Dryomorphs Micropithecus? Afropithecus Prohylobates Proconsul MIDDLE MIOCENE 15 LOWER MIOCENE 20 25 30 35 OLIGOCENE Millions of years ago UPPER MIOCENE Omomyiformes Afrotarsius Branisella Aegyptopithecus Propliopithecus Oligopithecus Catopithecus 40 EOCENE 45 Adapiformes 50 PALEOCENE 55 60 Purgatorius Strepsirhines May have given rise to the primates, in Africa 60 million years ago (probably tree-dwelling and adapted to gliding between trees) Haplorhines Oldest known anthropoids about 4030 million years ago Split between hominids and chimpanzees about 8-6 mya After Colin Groves Hominoid Evolution • Classification of the great apes and humans is difficult. • In the light of DNA comparisons, one solution is to place orangutans in the subfamily Ponginae and to combine African apes and humans in the subfamily Homininae. • In addition, a new level of classification is created, called tribes: • Hominini for humans and pre-humans • Gorillinae for the gorillas • Panini for the chimpanzees. Modern Classification - Hominoids • This modern classification of the hominoids addresses the genetic similarity of gorillas, chimpanzees, and humans. • Note that under this scheme, the term ‘hominid’ (i.e. a species from the Hominidae) would refer to a ‘great ape’ or human species. • This scheme is still not widely adopted. Activity •Complete the questions on page 371 to 373 In the Biozone book:
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