This document discusses hominin evolution and classification. It begins by classifying humans as mammals within the kingdom Animalia, phylum Chordata, class Mammalia, and order Primates. It then describes several early hominin species like Australopithecus afarensis and Homo habilis. Key developments discussed include bipedalism, brain growth, and basic tool use. The document also notes the emergence and spread of Homo erectus and later species like Homo neanderthalensis and Homo sapiens.

1. Hominin Evolution

2. Classification – where do we fit? Classification Kingdom Animalia Phylum Chordata Class Mammalia Who & (no. of living species) All animals (1,000,000) With spinal cord (50,000) Mammals (4,000)

3. What is a mammal?

4. Classification – where do we fit? Classification Kingdom Animalia Phylum Chordata Class Mammalia Sub-class Eutheria Order Primates Who & (no. of living species) All animals (1,000,000) With spinal cord (50,000) Mammals (4,000) Placental mammals (3750) Lemurs, monkeys, apes & humans (230)

6. shoulder joints which allow high degrees of movement in all directions;

7. five digits on the fore and hind limbs with opposable thumbs and big toes;

8. nails on the fingers and toes (in most species);

9. a flat nail on the hallux (in all extant species);

10. sensitive tactile pads on the ends of the digits;

11. orbits encircled in bone;

12. a trend towards a reduced snout and flattened face, attributed to a reliance on vision at the expense of olfaction

13. a complex visual system with stereoscopic vision, high visual acuity and color vision

14. a brain having a well developed cerebellum with posterior lobe and a Calcarine fissure

15. a large brain in comparison to body size, especially in simians;

16. differentiation of an enlarged cerebral cortex;

17. reduced number of teeth compared to primitive mammals;

18. three kinds of teeth;

19. a well-developed cecum;

20. two pectoral mammary glands;

21. typically one young per pregnancy;

22. a pendulous penis and scrotal testes;

23. a long gestation and developmental period;

25. Humans are Hominoids We share this classification with the great and lesser apes

26. Classification – where do we fit? Classification Order Primates . Sub-order Anthropoidea . SuperfamilyHominoidea Family Hominidae Subfamily Homininae Tribe Hominini Genus Homo Species sapiens Who & (no. of living species) Lemurs, monkeys, apes & humans (363) Monkeys, apes & humans (145) Apes & humans (20) Great apes & humans (7) Chimps & humans (2) Humans (1) Humans (1) Humans (1)

27. How long have we all been primates? ~ 65 mya lemurs and simians diverged ~ 40 mya new world monkeys (those found in the Americas) broke off ~ 31 mya old world monkeys and apes went separate ways ~ 18 mya the lesser apes (such as gibbons) diverged ~ 14 mya orang-utans diverged ~ 6-7 mya early hominoids evolved from a common ancestor shared with chimps, bonobos and gorillas

28. How long have we all been primates?

29. Using the molecular clock Comparisons are made between the various sequences of amino acids of primates. The calculated evolutionary distances are calibrated against the fossil record. Results indicated the divergence between humans and chimps to have occurred between 6 and 7 mya. Comparisons of DNA sequences have yielded similar results. These findings are not universally agreed upon.

30. Hominin Evolution In response to Darwin’s theory, people immediately wanted to find evidence of this “missing link” A supposedly transitional fossil between apes and humans Since this time we have not found a single missing link, but many ...

32. We have dated these finds to the best of our ability

33. What can we tell from these finds? We get an idea of the period during which the species existed. If two species co-existed one cannot be ancestral to the other They will not have been able to occupy the same niche, so They either existed in geographical areas or They did not compete for the dame food / habitat / shelter We get some idea of ancestral relationships A species can only be ancestral to one which it pre-dates and with which it did not co-exist.

34. The Australopithescines Species belonging to the Australopithecus genus Were small brained, large toothed and walked erect Can be loosely divided in to Graciles and Robusts The robusts displayed marked sexual dimorphism Eg. Males were larger with a distinct saggital crest Robust Gracile

35. Sexual Dimorphism Sexual (between the sexes) Di (two) morphism (forms) When the male and female of a species have a distinctly different appearance.

36. Sexual Dimorphism – the implications The presence of sexual dimorphism appears to have an impact on the social organisation of species. Gibbons (no sexual dimorph) – monogamous Chimps (some sexual dimorph) – harem controlled by group of males Gorillas (extreme sexual dimorph) – harem controlled by a single male GracileAustralopithacines are thought to have been similar to chimps in this respect.

37. The Australopithescines The graciles are thought to have been the line from which the genus Homo evolved.

38. Inferring diets From observation of teeth, tooth wear, jaw size and jaw musculature we can infer diet. The size of the zygomatic arch infers size of masseter and temporal jaw muscles We can see that robusts ate course vegetable matter and grailes ate less fibrous vegetable matter.

39. Inferring diets Herbivores require a much longer and more complex digestive tract. We can see evidence of this in the “pot-bellied” appearance inferred by australopithecine skeletons (a) as compared to human skeletons (b).

40. Bipedal locomotion Human A. Afarensis Chimp Locomotion was most likely bipedal as femur was at an angle, so legs positioned under weight of body. Weight falls on outside of locking knees

41. Bipedal locomotion – further evidence The foramen magnum of bipedal species is located further forward in the skull. The foramen magnum in A. Africanusis not as far forward as in modern H. Sapiens, but far more than in gorillas.

42. Bipedal locomotion – further evidence Bipedal species have a short hip bone and a bowl shaped pelvis. Chimp A. Africanus H. Sapiens

43. Australopithecines were intermediates Gorilla H. africanus Human

45. Brain case also displays intermediate cranial capacityChimp A. Afarensis Human Note intermediate size of diastema

46. Australopithecus afarensis

47. Australopithecus afarensis Fossils range from ~3.7-2.9 mya Brain size – 400cc Evidence of brachiation & bipedal locomotion No evidence of tool manufacture (although use of sticks / rocks as tools is highly likely) One of the most important find was the 40% complete skeleton of “Lucy”. Discovered in 1974 in the Afar Triangle in Ethiopia.

48. Deductions The fact that the Australopithecines were small-brained bipeds dispels the myth that the hominid brain development led to tool use It appears to be the other way around, bipedalism would have allowed us greater vision in the plains This freed up our hands to develop and explore tool use (a couple of million years later) Our brains developed in response to this new-found ability

49. The Earlier years The A. afarensis and A. africanus are two of the most well documented. Earlier notable finds include Ardipithecusramidus(4.4mya) Earlier hominids in the fossil record date back 6 to 7 mya.

50. Genus Homo First appeared in Africa ~2.4 mya Notable developments: smaller teeth, larger brain, flatter face Note the gradual enlargement of the brain case over time

51. Brain development Brain size is not as indicative of cognitive ability until compared with body mass

52. Homo habilis

53. Homo Habilis “Handy Man” Fossils range from ~2.4-1.6 mya Brain size – 640cc First evidence of tool manufacture – basic scrapers, cutters and choppers Most probably the first to include a substantial amount of meat in their diet – most likely carrion Thought to have co-existed with H. rudolphensis

54. Homo erectus

55. Homo Erectus “Upright Man” Fossils range from ~1.8 mya – 300,000 ya Brain size – 900cc More elaborate tools – still one piece but more skill in manufacture Displayed systematic hunting and controlled use of fire Communication through grunts and hand signals

56. H. erectus - communication Probably communicated through grunts and hand signals Fossil evidence shows that there were insufficient nerves running through the thoracic vertebrae for H. erectus to have the fine breathing muscles required for speech. H. erectus H. sapiens

58. H. Erectus leave africa Homo Erectus was the first hominid species to move out of sub-Saharan Africa. This map shows some of the locations where fossils have been found.

59. Other members of genus Homo H. Floresciensis“The Hobbit” 94,000 – 13,000 ya Brain size – 380 cc Only 1m tall Made tools & used fire Evolved from H. erectus H. heidelbergensis 400,000 – 40,000 ya Brain size – 1100-1200 cc Immediate predecessor of H. sapiens

61. Homo neanderthalensis

62. Homo neanderthalensis Fossils range from ~150,000 – 35,000 ya Brain size – 1400cc Made intricate tools, hunting systematically and controlled fire Buried dead, wore clothes & made shelters Communication through grunts and hand signals

63. Homo neanderthalensis Populations existed in Europe, the Middle East, Russia and North Africa. Co-existed with H. sapiens in these locations for some time. mtDNA indicates a common ancestor with H. sapiens 500,000 – 600,000 years ago. mtDNA also shows no evidence of interbreeding with H. sapiens. So why did they disappear? Was it disease or war or were they simply outcompeted for resources?

64. Homo sapiens

65. Homo Sapiens “Wise Man” Fossils range from ~130,000 ya – present Brain size – 1300cc As long as 30,000 yaH. Sapiens was burying their dead with intricate decorations and carved figurines. Earliest fossils found outside Africa were discovered in the Middle East and date to ~100,000 ya

68. Conflicting models of human evolution Predictions 1 and 3 have been shown to support the Out-of-Africa hypothesis. There is debate over whether some finds outside Africa constitute transitional forms or distant cousins of modern Homo sapiens

69. The “Out-of-Africa” model

73. Due to the nutritional benefits, humans able to metabolise lactose had a selective advantage

75. Cultural and Technological Evolution Can work in either direction with biological evolution Forwards Biological: bipedal with opposable thumbs Cultural: teach each other to make tools Technological: better suit tools to our needs Backwards Technological: Internet dating Cultural: Communicate with people in other countries Biological: Genetic traits enter the gene pool