PLACENTAL MAMMALS CLASSIFICATION

1. PLACENTAL MAMMALS CLASSIFICATION • Order Primates: • 200 species: • Prosimians: lemurs, tarsiers, and lorises • Anthropoids: monkeys, apes, and humans • Most are omnivores with teeth specialized for a varied diet • Most tend to live in social groups

2. PRIMATE

3. PRIMATE

4. Biogeography of Mammals • The history of Earth's geography has helped shape today's mammals • During the Paleozoic Era, the continents were one large landmass, and mammals could migrate freely across it • But as the continents drifted farther and farther apart during the Mesozoic and early Cenozoic Eras, ancestors of mammal groups were isolated from one another • Each landmass took with it a unique array of mammal groups

5. Biogeography of Mammals • Similar ecological opportunities on the different continents have produced some striking examples of convergent evolution in mammals • Thousands of kilometers apart, mammals evolved similar adaptations in form and function • When some of the landmasses merged in the late Cenozoic Era, mammals dispersed and intermingled in new habitats • Living mammals reflect the diversity that resulted from these events.

6. Convergent Evolution • Similar ecological opportunities on different continents have resulted in convergent evolution among these and other mammals • Mammals that feed on ants and termites evolved not once but five times in different regions • Powerful front claws; a long, hairless snout; and a tongue covered with sticky salvia are common adaptations in these insect-eating animals

7. Convergent Evolution

8. CONVERGENT EVOLUTION

9.  Primates and Human Origins • Our own species, Homo sapiens, belongs to the order that also includes lemurs, monkeys, and apes • Carolus Linnaeus named our order Primates, which means “first” in Latin

10. What Is a Primate? • Just what are primates “first” in? • When the first primates appeared, there was little to distinguish them from other mammals besides an increased ability to use their eyes and front limbs together to perform certain tasks • As primates evolved, however, several other characteristics became distinctive

11. What Is a Primate? • Primates share several important adaptations, many of which are extremely useful for a life spent mainly in trees • In general, primates have: • Binocular vision • Well-developed cerebrum • Relatively long fingers and toes • Arms that can rotate around their shoulder joints

12. HUMAN EVOLUTION • Paleoanthropologists: scientists who study human evolution • Classification of Humans: • Class: Mammalia • Order: Primates (erect mammal) • Opposable thumb: ability to grasp • Flattened nails rather than claws • Forward facing eyes: stereoscopic vision • Color vision (cones in retina) • Periodic vertical positioning (upright erect posture) • Shrews, Tarsiers, Lemurs, Monkeys, Apes (gibbons, chimpanzees, orangutans, gorillas), humans • Subgroup: Anthropoids (monkeys, apes, humans) • Welled developed collarbone, rotating shoulder joints, and partially rotating elbow joints gives skeletal strength and flexibility • Opposable thumb • Larger brain (cerebrum) (increase cranial capacity)

13. TARSIER

14. GIBBON

15. CHIMPANZEE

16. GORILLA

17. HUMAN EVOLUTION • Human Characteristics: • Bipedalisms: upright walking on two legs (unique human trait) • Broader Pelvis allowing for bipedal posture and supporting internal organs • Foramen Magnum: opening in the skull where the spinal cord enters is at the very bottom of the skull • Allows the vertebral column to support the head during bipedal walking • Sockets of pelvis positioned so that the leg bones extend vertically downward • Central opening larger in female • Larger cranial capacity (1400 cc) • Vertical forehead • Opposable thumb capable of moving farther across the hand • Big toe aligned with other toes helping distribute body weight during upright walking • V-shaped jaw (round shape) • No spacing between smaller teeth (omnivores)

18. Fingers, Toes, and Shoulders  • Primates normally have five flexible fingers that can curl around objects • Most also have flexible toes • Flexible digits (fingers and toes) enable many primates to run along tree limbs and swing from branch to branch with ease • Primates' arms are well adapted to climbing because they can rotate in broad circles around a strong shoulder joint • In most primates, the thumb and big toe can move against the other digits • The presence of this adaptation allows many primates to hold objects firmly in their hands or feet

19. HUMAN EVOLUTION

20. HUMAN EVOLUTION

21. Well-Developed Cerebrum  • The large and intricate cerebrum of primates—including a well-developed cerebral cortex—enables them to display more complex behaviors than many other mammals • For example, many primate species have elaborate social behaviors that include adoption of orphans and even warfare between rival primate troops

22. HUMAN EVOLUTION

23. Binocular Vision  • Many primates have a flat face, so both eyes face forward with overlapping fields of view • This facial structure gives primates excellent binocular vision • Binocular visionis the ability to merge visual images from both eyes, thereby providing depth perception and a three-dimensional view of the world • This is a handy adaptation for judging the locations of tree branches, from which many primates swing

24. TARSIER

25. Evolution of Primates • Humans and other primates evolved from a common ancestor that lived more than 65 million years ago • Early in their history, primates split into several groups • Primates that evolved from two of the earliest branches look very little like typical monkeys and are called prosimians • Members of the more familiar primate group that includes monkeys, apes, and humans are called anthropoids

26. Primate Evolution • This diagram illustrates the phylogeny of modern primates • The two main groups of primates are prosimians and anthropoids

27. Primate Evolution

28. Prosimians • With few exceptions, prosimians alive today are small, nocturnal primates with large eyes that are adapted to seeing in the dark • Many have doglike snouts • Living prosimians include the bush babies of Africa, the lemurs of Madagascar, and the lorises and tarsiers of Asia

29. Anthropoids  • Humans, apes, and most monkeys belong to a group called anthropoids, which means humanlike primates • This group split very early in its evolutionary history into two major branches: These branches became separated from each other as drifting continents moved apart • One branch, found today in Central and South America, is called the New World monkeys • After Columbus's voyage to America, Europeans began to use the term New World to refer to North and South America • New World monkeys, which include squirrel monkeys and spider monkeys, live almost entirely in trees • These monkeys have long, flexible arms that enable them to swing from branch to branch • New World monkeys also have a long, prehensile tail • A prehensile tail is a tail that can coil tightly enough around a branch to serve as a “fifth hand”

30. Anthropoids  • The other anthropoid group, which evolved in Africa and Asia, includes the Old World monkeys and great apes • Old World monkeys, such as langurs and macaques, spend time in trees but lack prehensile tails • Great apes, also called hominoids, include gibbons, orangutans, gorillas, chimpanzees, and humans • Recent molecular studies confirm that chimpanzees are humans' closest relatives among the great apes • Humans and chimps share an astonishing 98 percent of their DNA!

31. Hominid Evolution • Between 6 and 7 million years ago, the hominoid line gave rise to a branch that ultimately led to the ancestors and closest relatives of modern humans • The hominid family, which includes modern humans, displayed several distinct evolutionary trends • Fossil evidence shows that as hominids evolved over millions of years, they became able to walk upright and developed thumbs adapted for grasping • They also developed large brains

32. Hominid Evolution • The skull, neck, spinal column, hipbones, and leg bones of early hominid species changed shape in ways that enabled later species to walk upright • The figure at right shows some ways in which the skeletons of modern humans differ from those of gorillas • The evolution of this bipedal, or two-foot, locomotion was very important, because it freed both hands to use tools • Meanwhile, the hominid hand evolved an opposable thumb that enabled grasping objects and using tools

33. Hominid Evolution • Hominids also displayed a remarkable increase in brain size • Chimpanzees, our closest living relatives among the apes, have a brain size of 280 to 450 cubic centimeters • The brain of Homo sapiens, on the other hand, ranges in size from 1200 to 1600 cubic centimeters! • Most of the difference in brain size results from an enormously expanded cerebrum—the “thinking” area of the brain

34. Human and Gorilla Skeletons • Modern hominids walk upright on two legs; gorillas use all four limbs • According to the chart and illustration, what are the other differences between humans and gorillas?

35. Human and Gorilla Skeletons

36. Early Hominids  • Paleontologists have unearthed a treasure trove of hominid species • At present, most paleontologists agree that the hominid fossil record includes at least these genera—Ardipithecus, Australopithecus, Paranthropus, Kenyanthropus, and Homo—and as many as 20 separate species • This diverse group of hominid fossils covers roughly 6 million years • All these species are relatives of modern humans, but not all of them are human ancestors • To understand that distinction, think of your family • Your relatives may include aunts, uncles, cousins, parents, grandparents, and great-grandparents • Of these, only your parents, grandparents, and great-grandparents are your ancestors

37. HOMINID EVOLUTION • Hominids: subgroup of primates that includes human beings (Homo sapiens) and their immediate ancestors • Fossil record indicates a trend toward: • Bipedalism • Increased cranial capacity • Evolution of culture: • indicative of behavior that is dependent on learning and on passing knowledge from one generation to the next • Culture is all the information and ways of living built up by a group of human beings • Passed from one generation to the next

38. Early Hominids  • Almost a third of all known hominid species have been discovered in the last 20 years • This shows how rapidly knowledge of hominid fossils is growing • It also explains why hominid evolution is both fascinating and confusing • What once looked like a simple “human family tree” now looks more like a dense, branching shrub • Many questions remain about how fossil hominids are related to one another and to humans • Let's examine a few of the most important discoveries

39. Human-Fossil Seekers

40. HOMINID EVOLUTION • Australopithecus: • Earliest genus of hominids • Means “southern ape” • First found in South Africa • No evidence of tools • Four species: • Australopithecus afarensis • Australopithecus africanus • Australopithecus robustus • Australopithecus boisei

41. AUSTRALOPITHECUS

42. Australopithecus • One early group of hominids, members of the genus Australopithecus, lived from about 4 million to a million years ago • These hominids were bipedal apes that spent at least some time in trees • The structure of their teeth suggests a diet rich in fruit • Some Australopithecus species seem to have been human ancestors, while others formed separate branches off the main hominid line

43. Australopithecus • The best known species is Australopithecus afarensis—described from a remarkably complete female skeleton, nicknamed Lucy, who stood only about 1 meter tall • The humanlike footprints, which are between 3.8 and 3.6 million years old, were probably made by members of the same species as Lucy • Since Australopithecus fossils have small brains, the Laetoli footprints show that hominids walked bipedally long before large brains evolved

44. Australopithecus Footprints  • Between 3.8 and 3.6 million years ago, members of a species of Australopithecus made these footprints at Laetoli in Tanzania • The footprints show that hominids walked upright millions of years ago

45. Australopithecus Footprints 

46. AUSTRALOPITHECUS

47. HOMINID EVOLUTION • Australopithecus afarensis: • Oldest fossil dated between 3 million and 3.5 millions years old (Lucy) • Shorter than modern humans (approximately 1.5m or 5 ft tall) • Bone structures indicate bipedalism • Cranial capacity between 380 and 450 cc (1/3 modern humans)

48. HOMINID EVOLUTION • Australopithecus africanus: • Lived 2.2 million to 3 million years ago • Slightly taller and heavier than A. afarensis • Cranial capacity slightly larger than A. afarensis: between 430 and 550 cc

49. HOMINID EVOLUTION • Australopithecus robustus: • Southern Africa • Australopithecus boisei: • Eastern Africa • Both species: • Lived between 1 million and 2 million years ago • Heavier skulls than A. africanus • Larger back teeth than A. africanus • Larger cranial capacity than A. africanus: between 450 and 600 cc

50. Paranthropus • Three later species, which grew to the size of well-fed football linebackers, were originally placed in the genus Australopithecus • However, they are now usually placed in their own genus, Paranthropus • The known Paranthropus species had huge, grinding back teeth • Their diets probably included coarse and fibrous plant foods like those eaten by modern gorillas • Most paleontologists now place Paranthropus on a separate, dead-end branch of our family tree