1. NOTES: Ch 34 - Mammals & Primate / Human Evolution (34.7-34.8)

2. Class: MAMMALIA ● Mammals possess unique derived characteristics:
1) Provide young with milk (mammary glands)
2) Internal fertilization; some embryo development within uterus before birth
3) Hair

3. Class: MAMMALIA ● Mammals possess unique derived characteristics:
4) Endothermic (high metabolic rate)
5) Larger brain (than other vertebrates of similar size)
6) Differentiated teeth

4. Mammals… ● Most mammals are EUTHERIANS (a.k.a. “placental” mammals”)
-highly developed at birth
-most are terrestrial, but some are marine
-important grazers and browsers in terrestrial ecosystems

5. ● Primates have been present for 65 million years and are defined by shared derived characteristics shaped by natural selection for living in trees:
● limber shoulder joints
● dexterous hands
● sensitive fingers with nails
(not claws)
● eyes close together
● excellent hand-eye coordination
● parental care with usually single births and long nurturing
● complex social behavior

6. New World monkey: spider monkey (b) Old World monkey: macaque
Figure New World monkeys and Old World monkeys.
(a)
New World monkey: spider monkey
(b) Old World monkey: macaque 6

7. (a) Gibbon (b) Orangutan (c) Gorilla (d) Chimpanzees (e) Bonobos
Figure Nonhuman apes.
(e) Bonobos 7

8. ● Most anthropologists believe that humans and apes diverged from a common ancestor 6-8 million years ago

9. Lemurs, lorises, and bush babies
ANCESTRAL PRIMATE
Tarsiers
New World monkeys
Old World monkeys
Anthropoids
Gibbons
Orangutans
Gorillas
Figure A phylogenetic tree of primates.
Chimpanzees and bonobos
Humans 60 50 40 30 20 10
Time (millions of years ago) 9

10. Figure Nonhuman apes.
(d) Chimpanzees 10

11. Figure Nonhuman apes.
(e) Bonobos 11

12. Derived Characters of Humans
● A number of characters distinguish humans from other apes
-Upright posture and bipedal locomotion
-Larger brains capable of language, symbolic thought, artistic expression, the manufacture and use of complex tools
-Reduced jawbones and jaw muscles
-Shorter digestive tract

13. The Earliest Hominins
● The study of human origins is known as paleoanthropology
● Hominins are more closely related to humans than to chimpanzees
● Paleoanthropologists have discovered fossils of about 20 species of extinct hominins

14. Paranthropus robustus
Homo ergaster
Homo neanderthalensis
Homo sapiens ?
Paranthropus boisei
0.5
1.0
1.5
Australopithecus africanus
2.0
Kenyanthropus platyops
2.5
Australopithecus garhi
Australo- pithecus anamensis
Millions of years ago
3.0
Homo erectus
3.5
Homo rudolfensis
Homo habilis
4.0
4.5
Figure A timeline for some selected hominin species.
Australopithecus afarensis
5.0
Ardipithecus ramidus
5.5
6.0
Orrorin tugensis
6.5
Sahelanthropus tchadensis
7.0 14

15. ● Misconception: Early hominins were chimpanzees
**Correction: Hominins and chimpanzees shared a common ancestor
● Misconception: Human evolution is like a ladder leading directly to Homo sapiens
**Correction: Hominin evolution included many branches or coexisting species, though only humans survive today

17. The First Humans: Australopiths
● Australopiths are a paraphyletic assemblage of hominins living between 4 and 2 million years ago
● Some species, such as
Australopithecus
afarensis walked
fully upright

18. The First Humans: Australopiths
Figure Evidence that hominins walked upright 3.5 million years ago.
(a) The Laetoli footprints
(b) Artist’s reconstruction of A. afarensis 18

19. Chimpanzee Australopithecus africanus Homo sapiens
The First Humans:
● Australopithecus africanus:
walked upright; humanlike teeth and hands
brain was about 1/3 size of modern humans
4 million years ago; existed for 3 million yrs.
Chimpanzee Australopithecus africanus Homo sapiens

20. ● Australopithecus afarensis (“Lucy”)
upright posture
evidence of coexistence with A. africanus for about 1 million years

22. ● Australopithecus anamensis: about 4 m.y.a.
● Ardipithecus ramidus: about 4.4 m.y.a.

23. ● hominids walked upright for two million years without a substantial increase in brain size!
● this posture may have freed the hands for other things such as gathering food or caring for infants

24. Early Homo
● The earliest fossils placed in our genus Homo are those of Homo habilis, ranging in age from about 2.4 to 1.6 million years
● Stone tools have been
found with H. habilis, giving
this species its name,
which means “handy man”

25. adult cranial capacity (range in cm3)
Homo habilis
adult cranial capacity (range in cm3)
Chimpanzees
Australopithecines
early transitional humans
modern humans
● enlargement of brain is evident in fossils dating back to about m.y.a. (650 cc vs. 500 cc)
● simple stone tools found with larger-brained fossils
● coexisted with A. africanus for almost 1 million years
 (A. africanus was an evolutionary “dead end”)

26. Early Homo
● Homo ergaster was the first fully bipedal, large-brained hominid
● The species existed between 1.9 and 1.5 million years ago
● Homo ergaster shows a significant
decrease in sexual
dimorphism (a size
difference between
sexes) compared with
its ancestors

27. Homo erectus & descendants
● taller and larger brain than H. habilis (1200 cc)
● first hominid to migrate out of Africa
● 1.8 m.y.a. to 250,000 years ago

28. ● H. erectus remains have been found on other continents
● diet shifted to include a larger portion of meat
● intelligence allowed them to survive in colder climates (lived in huts or caves, built fire, wore clothing, designed more refined tools)

29. **best known descendants of H. erectus are Neanderthals!
-lived in Europe, Middle East, & Asia
-they were thick-boned with a larger brain, they buried their dead, and they made hunting tools
-350,000 to 28,000 years ago

32. The Origin of Modern Humans (2 theories):
1) Multiregional Model
2) Monogenesis Model
(“Out of Africa” model)

33. 1) Multiregional Model
● proposes that modern humans evolved in parallel along the same lines in different parts of the world
*if true, then…
● the geographic diversity of humans originated between 1-2 m.y.a. when H. erectus first spread from Africa to other continents

36. 2) Monogenesis Model (“Out of Africa” model)
● proposes that modern humans evolved from the H. erectus group(s) that stayed in Africa; they then dispersed from Africa, displacing the Neanderthals and other hominids (suggests the Neanderthals were NOT ancestors of modern humans since they coexisted and were probably evolutionary dead ends)
*if true, then…
● the geographic diversity of humans developed within the last 100,000 years

39. ● Mitochondrial DNA (mtDNA) studies support the monogenesis model.
                                                    

41. Homo Sapiens ● Homo sapiens appeared in Africa by 195,000 years ago
● All living humans are descended from these African ancestors

42. Homo Sapiens Figure 34.51 A 160,000-year-old fossil of Homo sapiens.42

43. Homo Sapiens
● The oldest fossils of Homo sapiens outside Africa date back about 115,000 years and are from the Middle East
● Humans first arrived in the New World sometime before 15,000 years ago
● Homo sapiens
were the first group
to show evidence
of symbolic and
sophisticated
thought

44. Cultural Evolution:
● the basis of culture is learning from the experiences of earlier generations
● transmission of information is by written and spoken language

45. Cultural Evolution & Learning
*Cultural learning facilitated spread of domesticated plants and animals
 Human societies converted from hunters & gatherers to PASTORAL (herding large animals) and AGRICULTURAL

46. Human Population Growth:
Three phases:
1) Tool use: lasted about
1 million years
-POP. = 5 million ppl.
2) Domestication of plants
& animals: lasted about
8,000 years
-POP. = 500 million ppl.

48. Human Population Growth:
3) Industrial Revolution: started about 300 years ago
-CURRENT POP. = 7.0 billion ppl.
-EST. POP. by 2050 = 11 billion ppl.