1. Chapter 8
Hominid Origins

2. Chapter Outline Early Primate Evolution Miocene Fossil Hominids
Definition of Hominid
The Bipedal Adaptation
Biocultural Evolution: The Human Capacity for Culture
Paleoanthropology as a Multidisciplinary Science

3. Chapter Outline Dating Methods Early Hominids from Africa
Australopithecus from East Africa
Early Homo
South African Hominids
Interpretations: What Does It All Mean?

4. Early Primate Evolution
The roots of the primate order go back to the beginnings of the placental mammal radiation circa 65 m.y.a.
The earliest primates were diverging from quite early primitive placental mammals.
A vast number of fossil primates from the Eocene (55–34 m.y.a.) have been discovered and now total more than 200 recognized species.

5. Eocene Primates
Fossil primates from the Eocene display distinctive primate features.
Looking at the whole array of Eocene primates, it is certain that they were:
Primates
Widely distributed
Mostly extinct by the end of the Eocene.

6. Early Eocene Primates: Features
Chinese fossils dating from the early Eocene (55–45 m.y.a. have three interesting features:
Forward rotation of the eyes, a feature that makes them distinct from the lemur-loris lineage.
The cranium shows small eye sockets, suggesting they may have been diurnal.
They were all apparently extremely small, weighing less than 1 ounce.

7. Oligocene Primates
The Oligocene (34–23 m.y.a.) yielded fossil remains of several species of early anthropoids.
By the early Oligocene, continental drift had separated the New World from the Old World.
It has been suggested that late in the Eocene or very early in the Oligocene, the first anthropoids arose in Africa and reached South America by “rafting” over the water separation on drifting chunks of vegetation.

8. Major Events in Early Primate Evolution

9. Miocene Hominoid Distribution, From Fossils Thus Far Discovered

10. Miocene Fossil Hominoids
African forms (23–14 m.y.a.)
Especially from western Kenya, these hominoids are, in many ways, primitive.
European forms (16–11 m.y.a.)
From scattered localities in France, Spain, Italy, Greece, Austria, Germany, and Hungary, most are quite derived.

11. Miocene Fossil Hominoids
Asian forms (16–7 m.y.a.)
The largest and most varied group from Turkey through India/Pakistan and east to southern China, most are highly derived.

12. Miocene Hominoid Fossils
These are hominoids—more closely related to the ape-human lineage than Old World monkeys.
Mostly large-bodied hominoids, more akin to the lineages of orangutans, gorillas, chimpanzees, and humans than smaller-bodied apes.
Most of the Miocene forms thus far discovered are so derived that they are probably not ancestral to any living form.

13. Miocene Hominoid Fossils
One lineage that appears well established relates to Sivapithecus from Turkey and Pakistan. This form shows some derived facial features similar to the modern orangutan, suggesting a fairly close evolutionary link.
Evidence of definite hominids from the Miocene has not yet been indisputably confirmed. However, exciting new finds from Kenya, Ethiopia, and Chad (the latter dating as far back as 7 m.y.a.) suggest that hominids diverged sometime in the latter Miocene.

14. Patterns of Evolution Mosaic evolution
Evolutionary pattern in which physiological and behavioral systems evolve at different rates.
Biocultural evolution
Biology makes culture possible and developing culture further influences biological evolution.

15. Mosaic Evolution of Hominid Characteristics
Locomotion
Modern Homo sapiens
Bipedal: shortened pelvis; body size larger; legs longer; fingers and toes not as long
Early hominid
Bipedal: shortened pelvis; differences from later hominids, smaller body size and long arms relative to legs; long fingers and toes; probably capable of considerable climbing
Miocene, generalized hominoid
Quadrupedal: long pelvis; some capable of considerable arm swinging, suspensory locomotion

16. Mosaic Evolution of Hominid Characteristics
Brain
Modern Homo sapiens
Greatly increased brain size—highly encephalized
Early hominid
Larger than Miocene forms, moderately encephalized; prior to 6 m.y.a., no more encephalized than chimpanzees
Miocene, generalized hominoid
Small compared to hominids, but large compared to other primates; a fair degree of
encephalization

17. Mosaic Evolution of Hominid Characteristics
Dentition
Modern Homo sapiens
Small incisors; canines further reduced; molar tooth enamel caps thick
Early hominid
Moderately large incisors; canines somewhat reduced; molar tooth enamel caps very thick
Miocene, generalized hominoid
Large front teeth (including canines); molar teeth variable, depending on species; some have thin enamel caps, others thick enamel caps

18. Mosaic Evolution of Hominid Characteristics
Toolmaking Behavior
Modern Homo sapiens
Stone tools found after 2.5 m.y.a.; increasing trend of cultural dependency apparent in later hominids
Early hominid
In earliest stages unknown; no stone tool use prior to 2.5 m.y.a.; more oriented toward tool manufacture and use than chimpanzees
Miocene, generalized hominoid
Unknown—no stone tools; probably had capabilities similar to chimpanzees

19. Revised Classification of Hominoids

20. The Bipedal Adaptation
Efficient bipedalism as the primary form of locomotion is seen only in hominids.
Advantages of bipedalism:
Freed the hands for carrying objects and for making and using tools.
In the bipedal stance, animals have a wider view of the surrounding countryside.
Bipedal walking is an efficient means of covering long distances.

21. Obligate Bipedalism
Bipedalism as the only form of hominid terrestrial locomotion.
Since major anatomical changes in the spine, pelvis, and lower limb are required for bipedal locomotion, once hominids adapted this mode of locomotion, other forms of locomotion on the ground became impossible.

22. Major Features of Hominid Bipedalism
The foramen magnum (shown in red) is repositioned farther underneath the skull, so that the head is more or less balanced on the spine (and thus requires less robust neck muscles to hold the head upright).

23. Major Features of Hominid Bipedalism
The spine has two distinctive curves—a backward (thoracic) one and a forward (lumbar) one—that keep the trunk (and weight) centered above the pelvis.

24. Major Features of Hominid Bipedalism
The pelvis is shaped more in the form of a basin to support internal organs; moreover, the ossa coxae are shorter and broader, thus stabilizing weight transmission.

25. Major Features of Hominid Bipedalism
Lower limbs are elongated, as shown by the proportional lengths of various body segments (e.g., in humans the thigh comprises 20% of body height, while in gorillas it comprises only 11%).

26. Major Features of Hominid Bipedalism
The femur is angled inward, keeping the legs more directly under the body; modified knee anatomy also permits full extension of this joint.

27. Major Features of Hominid Bipedalism
The big toe is enlarged and brought in line with the other toes; in addition, a distinctive longitudinal arch forms, helping absorb shock and adding propulsive spring.

28. Paleoanthropology
Paleoanthropology is defined as the study of early humans.
Paleoanthropologists reconstruct the anatomy, behavior, and ecology of our ancestors:
It is a diverse multidisciplinary pursuit seeking to reconstruct every bit of information possible concerning the dating, anatomy, behavior, and ecology of our hominid ancestors.

29. Components of Paleoanthropology
Physical Sciences
Biological Sciences
Social Sciences
Geology
Physical anthropology
Archaeology
Geomorphology
Ecology
Ethnoarchaeology
Geophysics
Primatology
Cultural anthropology
Chemistry
Psychology
Taphonomy

30. Dating Methods
Paleoanthropologists use two types of dating methods to tell us the age of sites and fossils:
Relative dating determines only whether an object is older or younger than other objects.
Chronometric (absolute) dating provides an estimate of age in years based on radioactive decay.

31. Relative and Chronometric Dating
Relative Dating
Chronometric Dating
Examples
Stratigraphy
Fluorine Dating
K/Ar
Radiocarbon (14 C)
Fission-track
Methodological basis
Provides a sequence only; i.e., no estimates in actual number of years
Most techniques* are radiometric; i.e., steady decay of radioactive isotope provides estimate in actual number of years

32. Relative Dating Techniques
Stratigrapy - based on the law of superposition, that a lower stratum (layer) is older than a higher stratum.
Fluorine analysis applies to buried bones and groundwater seepage. Bones incorporate fluorine during fossilization.

33. Relative Dating Techniques
Biostratigraphy - related to changes in the dentition of animals.
Paleomagnetism - based on the shifting of the geomagnetic pole.

34. Chronometric Dating Techniques
The age of an object can be determined by measuring the rate of disintegration:
Potassium/argon (k/Ar) dating involves the decay of potassium into argon gas. K/Ar has a half-life of 1.25 billion years.
Carbon-14 is a radiometric method commonly used by archeologists. Carbon 14 has a half-life of 5730 years.

35. Position of the Foramen Magnum
(a) a human and (b) a chimpanzee.
Note the more forward position in the human cranium.

36. Key Very Early Fossil Hominid Discoveries (pre-Australopithecus)
Site
Dates (m.y.a.)
Hominids
East Africa
Middle Awash (Ethiopia; five localities)
5.8–5.2
Ardipithecus
Aramis (Ethiopia)
4.4
Ardipithecus ramidus
Central Africa
Tugen Hills
~6.0
Orrorin tugenensis
Toros-Menalla
~7.0
Sahelanthropus tchadenis

37. Features of Australopithecus
They are all clearly bipedal (although not necessarily identical to Homo in this regard).
They all have relatively small brains (i.e., at least compared to Homo).
They all have large teeth, particularly the back teeth, with thick to very thick enamel on the molars.

38. Laetoli Dated at between 3.5 and 3.7 m.y.a.
Fossilized hominid footprints were found in an ancient volcanic bed.
Despite agreement that these individuals were bipedal, some researchers feel they were not bipedal in the same way as modern humans.

39. Hadar (Afar Triangle) Dating suggests a range from 3.9 to 2.3 m.y.a.
Recovered:
"Lucy" an Australopithecus afarensis female, was recovered here.
Group of bones representing 13 individuals, including 4 infants, suggest a social unit died at the same time.
Some stone tools may be 2.5 million years old, making them the oldest cultural evidence yet found.

40. Koobi Fora (East Lake Turkana)
This site yielded the richest assemblage of Plio-Pleistocene hominids from the African continent.
Most of the hominids date to 1.8 m.y.a., others date back to 3.3 m.y.a.
150 hominid specimens recovered at Koobi Fora represent at least 100 individuals.

41. West Turkana
Two important discoveries:
Discovery of a nearly complete 1.6 m.y.a. Homo erectus adolescent.
Discovery of “the black skull”, a well-preserved 2.4 million year old skull which caused a major reevaluation of Plio-Pleistocene evolution.

42. Olduvai Gorge
Louis and Mary Leakey conducted continuous excavations from the 1930's to early 1980.
Paleontological evidence includes more than 150 species of extinct animals which can provide clues to the ecological conditions of early hominid habitats.

43. South African Sites
The first australopithecine “the missing link” between apes and humans was discovered at a quarry at Tuang.
As the number of discoveries accumulated, it became clear that the australopithecines were not simply aberrant apes.
The acceptance of the australopithecines as hominids required revision of human evolutionary theory.

44. Estimated Body Weights and Stature in Plio-Pleistocene Hominids
Male
Female
A. afarensis
99 lb
64 lb
59 in.
41 in.
A. africanus
90 lb
65 lb
54 in.
45 in.
South African “robust”
88 lb
70 lb
52 in.
43 in.
East African “robust”
108 lb
75 lb
49 in.
H. habilis
114 lb
62 in.

45. Steps in Interpreting Homind Evolutionary Events
Selecting and surveying sites.
Excavating sites and recovering fossil hominids.
Designating individual finds with specimen numbers for clear reference.
Cleaning, preparing, studying, and describing fossils.

46. Steps in Interpreting Homind Evolutionary Events
Comparing with other fossil material—in chronological framework if possible.
Comparing fossil variation with known ranges of variation in closely related groups of living primates and analyzing ancestral and derived characteristics.
Assigning taxonomic names to fossil material.

47. Groups of Plio-Pleistocene Hominids
Specimens represent 200 individuals from South Africa and more than 300 from East Africa.
Divided into four broad groupings:
Set I Basal Hominids.
Set II Early Primitive Australopithecus.
Set III Later, more derived Australopithecus.
Set IV Early homo.

48. Set I. Basal Hominid (4.4 m.y.a.)
The earliest and most primitive remains are those from Aramis.
They have been classified as Ardipithecus ramidus, a different genus from all other Plio-Pleistocene forms.

49. Set II. Early Primitive Australopithecus, 4.2-3.0 m.y.a.)
The hominids from Laetoli and Hadar are assigned to Australopithecus afarensis.
A. afarensis is so primitive in the majority of dental and cranial features that if it were not for evidence of bipedalism, this primate would not be classified as a hominid.

50. Set III. Later, More Derived Australopithecus (2.5-1.0 m.y.a.)
Robust Australopithecines
Larger body size
Small cranial capacities
Very large, broad faces
Massive back teeth and lower jaws
Gracile Australopithecines
Different face dentition

51. Set IV. Early Homo (2.4-1.8 m.y.a.)
The earliest appearance of our genus, Homo may be as ancient as the robust Australopithecines.
Leakey named these specimens Homo habilis ("handy man")
H. habilis differs from Australopithecus in cranial cavity and dental proportions.

52. Quick Quiz

53. 1. The primary task of an archeologist at a paleoanthropological site is to
search for hominid "traces."
reconstruct the ancient environment of the site.
establish the relationships of any fossil humans recovered.
perform dating techniques to establish the time period.

54. Answer: a
The primary task of an archeologist at a paleoanthropological site is to search for hominid "traces."

55. 2. _________________ dating indicates that something is older or younger than something else.

56. Answer: Relative
Relative dating indicates that something is older or younger than something else.

57. 3. The radiometric dating technique used to date material from a few hundred years old to 75,000 years old is ___________.

58. Answer: Carbon-14
The radiometric dating technique used to date material from a few hundred years old to 75,000 years old is ___________.

59. 4. Efficient bipedalism as a primary form of locomotion is only seen in hominids.
True
False

60. Answer: True
Efficient bipedalism as a primary form of locomotion is only seen in hominids.