Hominid Evolution: On The Origin of Humans

1. Hominid Evolution:On The Origin of Humans

2. What is a Hominid? • The term “hominid” is also used in the more restricted sense as “hominins” • Humans and relatives of humans closer than chimpanzees • Bipedal • Modern man is the only member of this group alive today

3. Hominid Sites • Earliest fossil hominid sites are in Africa • They now span the latest Miocene to the early Pleistocene from about 6-7 mya to about 1.6 mya • The major groups of sites are: • Ethiopia = Middle Awash valley & Hadar (Australopithecus afarensis) • Kenya = Lake Turkana • Tanzania = Olduvai Gorge • South Africa = various sites in limestone caverns centered around Sterkfontein

4. What Makes A Hominid? - Bipedalism • Primary feature distinguishing hominids from other hominoids is walking erect on two legs – erect bipedalism • Adaptations for bipedalism in the partial skeleton of “Lucy,” an australopithecine ( 3.2 mya) clearly seen in the hip, spine and leg bones

5. Why did bipedalism become the primary adaptation of hominids? Climate Change resulting in forest habitat being replaced by grasslands.

6. Advantages of Bipedalism 1. Carrying behavior 2. Reduction of overall heat stress - facilitates heat loss through convection by exposing body to air currents, only humans have sweat glands that produce moisture to cool body 3. Most energy efficient way to travel long distances 4. Allows for better vision in open environments & defensive action against predators by freeinghands to throw objects

7. Evidence for Early Bipedalism • The record of bipedalism is most graphically preserved in the fossilized footprints at Laetoli, Tanzania, 3.6 mya • Tracks of 2 individuals were uncovered in volcanic ash by Mary Leakey (1978-79) • Footprints were left by 2 australopithecines in damp volcanic ash of Laetoli • Notice how close the tracks are!

8. Laetoli Footprints • Laetoli footprints clearly show that the creatures who made them were fully bipedal • Big toe hardly diverges from the rest of the foot, unlike in apes • Gait = “heel-strike” followed by “toe-off” – the way modern humans walk

9. Laetoli Reconstruction • 2 early hominids walk bipedally across an open ash field produced by an erupting volcano. • Rain wet the volcanic ash & footprints filled up with more ash, and were thus preserved. • Footprints reveal that our ancestors walked upright with a gait very similar to our own.

10. First Adaptive Radiation • 7-6 mya in the late Miocene, potential last common ancestors between humans and apes 1. Sahelanthropustchadensis 7-6 mya in Chad (North Central Africa) 2. Orrorintungenensis 6 mya in Kenya (East Africa) Note: These organisms were forest adapted.

11. 1. Sahelanthropus tchadensis • Discovered in Chad (7-6 mya) • Most complete cranium from this time period • Mosaic of ape & human-like features, but at the “ape grade” of evolution: • Cranial capacity (320-380 cc) • U-shaped upper jaw • Very wide distance between the orbits • Large, thick continuous brow ridge • Human-like flat face • Human-like dentition

12. 2. Orrorin tungenensis • Fossils from Tugen Hills in Kenya have been dated to about 6 mya • Earliest Evidence for • Walking on Two Legs?

13. Orrorin tungenensis (cont.) • Fossils Include: upper portion of a femur, lower portion of the humerus, some lower jaw fragments, & teeth • Arm bone: virtually identical to that of a chimpanzee • Femur: more human-like, most important for showing adaptations for walking on 2 legs • Was Orrorin a direct human ancestor, or a common ancestor of chimps and humans?

14. Second Adaptive Radiation • 5-4 mya in early Pliocene, first true hominids 1. Ardipithecusramidus 5.5-4.5 mya in Ethiopia (East Africa) 2.Australopithecus anamensis 4.2-3.9 mya in Kenya (East Africa) Note: These organisms were forest adapted and fully bipedal.

15. 1. Ardipithecus ramidus Earliest True Hominid or Last Common Ancestor? LAST COMMON ANCESTOR OF CHIMPS & HUMANS MOST LIKELY HAD A MIX OF FEATURES: SOME RETAINED IN CHIMPS, OTHERS RETAINED IN HUMANS!

16. Ardipithecus ramidus (cont.) • Between 4.5 and 5.5 mya from the Middle Awash valley site in Ethiopia • Fossil Remains very fragmentary: limb bones, toe bones, jaws & teeth • Straight toe bones suggest it may have been bipedal • A mosaic of features seen in later hominids & modern chimpanzees

17. 2. Australopithecus anamensis • Lake Turkana Region of Kenya • 4.2-3.9 mya • Probably walked upright • Teeth enamel thicker than Ardipithecusramidus, so diet included hard foods

18. Australopithecus anamensis (cont.) • Fossil Remains very fragmentary • Those shown here include: • Jawbone • part of the front of the face • parts of an arm bone (radius) • fragments of a lower leg bone (tibia)

20. Third Adaptive Radiation • 4-3 mya in middle Pliocene, many hominids 1. Australopithecus afarensis (“Lucy”) 4-3 mya in East Africa 2.Australopithecus africanus 4-2.5 mya in South Africa 3. Kenyanthropus platyops 3.5-3.2 mya in Kenya Note: These organisms lived in open woodlands & along wooded streams in the savannas, ate fruits and soft foods, maybe had a tool-culture like modern chimps

21. 1. Australopithecus afarensis • 4-3 mya in East Africa • Pelvis & leg bones resemble modern humans • Sexual dimorphism (males larger with sagittal crest) • Tree climbers (curved fingers & toes) Ape-like Features: • Small brain case (430 cc.) • Prognathic (jutting out) face • U-shaped palate (v. parabolic shape)

22. Australopithecus afarensis

23. A. afarensis Skeleton - Lucy

24. 2. Australopithecus africanus • 4-2.5 mya in Transvaal region of South Africa • 1924: 1stAustralopithicine to be described by Raymond Dart! • Globular cranium, slightly higher ratio of brain to body size than A. afarensis • Face less prognathic than A. afarensis • Proportions of arm to leg lengths may be more ape-like than A. afarensis

25. Australopithecus africanus Australopithecus africanus best known A. africanus cranium(front & lateral views) Most complete A. africanus skull Taung Child

26. A. afarensis verses A. africanus A. afarensis Australopithecus afarensis Australopithecus africanus

27. 3. Kenyanthropus platyops • 3.5-3.2 mya: found in 2001 west of Lake Turkana in Kenya • Ape-like features: small ear canal, small brain case • Human-like features: flat face, small molars • Importance: flat face appeared early in evolution, alongside the range of other facial forms. Evidence that evolution is not linear or progressive.

28. Kenyanthropus platyops

29. Fourth Adaptive Radiation • 3-1 mya in late Pliocene, more “robust” hominids 1. Paranthropus boisei 2.2-1.2 mya in East Africa 2. Paranthropus robustus 2-1 mya in South Africa 3. Australopithecus garhi 3-2 mya in East Africa Note: Lived in open dry woodlands & savannas. The robust species are famous for eating hard-to- chew food, like seeds, nuts, and roots. May have used tools to dig for roots in dry seasons.

30. 1. Paranthropus boisei • 2.2-1.2 mya in East Africa: Ethiopia, Kenya, Tanzania • Largest teeth found in any hominid! • Referred to as “hyper-robust” due to massive molars and premolars • Skull: broad, short face with flaring cheek bones, relatively small brain, pronounced sagittal crest in males • Skull and dental features are adaptations for heavy chewing!

31. Paranthropus boisei (KNM-ER 406)

32. Paranthropus boisei (KNM-ER 406)

33. 2. Paranthropus robustus • 2-1 mya in South Africa • Short, broad face with deep zygomatic arches (cheek bones). Larger individuals have sagittal crests. • Large molars covered with thick enamel • Wear patterns on teeth: herbivorous diet of hard resistant foods such as seeds, nuts, roots • Lived in grasslands near rivers and wetlands

34. Paranthropus robustus

35. 3. Australopithecus garhi • 3-2 mya in East Africa: spotty fossil record, cranial & dental remains found in 1999 in Bouri, Ethiopia • Bones of antelopes, horses, and other animals with cut marks made by stone tools: butchering animals & smashing bones for marrow. First meat eaters? • Molars too large to be early Homo genus • Ape-like long lower arm, human-like upper arm & leg • Mixed traits: classified as a new species, maybe ancestor of early Homo genus

36. Australopithecus garhi

37. Australopithecus garhi One surprise in the A. garhi skull was enormous back teeth, instead of smaller ones seen in later Homospecies

38. Australopithecus garhi • EARLIEST BUTCHERS: • Signs that hominids scraped & smashed animal bones, like this antelope tibia, 2.5 mya • Earliest documented percussion marks made by hominids, presumably extracting fatty marrow from these bones

39. Rise of the Genus Homo • Homo habilis – “Handy Man” • Homo erectus – or Homo ergaster in Africa • Homo heidelbergensis – “Archaic Homo sapiens” • Homo sapiens neanderthalensis - Neanderthal • Homo sapiens sapiens – Modern Man

40. Homo habilis 2.4 – 1.4 MYA • Slightly larger braincase and smaller face and teeth than Australopithecus • Still retains ape-like features of long arms and moderately prognathic face • Average height = 3’4’’ to 4’5’’ • Average weight = 70 lbs.

41. Homo habilis • Thick tooth enamel suggests they had an omnivorous diet, but were capable of eating fairly tough foods like leaves and woody plants By this time, the feet of early humans had a modern-type arch

42. Homo erectus 1.89 MYA – 143,000 years ago • Modern human-like body proportions indicate adaptations for living exclusively on the ground • Expanded braincase relative to the size of the face • Left Africa and spread into Asia • Longest lived early human relative (9 times longer than we have been around so far) • Used fire (warmth, cooking) • Evidence they cared for the sick and old (see skull to left) • Average height = 4’9’’ to 6’1’’ • Average weight = 88-150 lbs.

43. Homo erectus Turkana boy fossil Hand axe – first major innovation in stone tool technology

44. Homo heidelbergensis • Very large brow ridge • Larger braincase and flatter face than earlier human ancestors • Short, wide bodies adapted to living in colder climates • Most likely candidate to have been common ancestor between Neanderthals and modern humans • Average height = males 5’9’’, females 5’2’’ • Average weight = males 136 lbs., females 112 lbs. 700,00 – 200,00 years ago

45. Homo heidelbergensis • Used wooden spears to routinely hunt large animals • Built shelters out of wood and rock

46. Homo sapiens neanderthalensis • Short, stocky bodies and huge noses were adaptations for living in cold environment • Larger braincase than modern man • Sophisticated tools, used shelters, wore clothing • First human ancestor to bury their dead and mark the graves • Modern humans led to their extinction but unclear as to exactly how • Average height = males 5’5’’, females 5’1’’ • Average weight = males 143 lbs., females 119 lbs. 200,000 – 28,000 years ago

47. Homo sapiens neanderthalensis Ornamental jewlery La Ferrassie 1 – Most complete Neanderthal skull ever found

48. Homo sapiens sapiens • Originated in Africa 200,000 years ago • Highly vaulted, thin-walled skull led to more developed frontal lobe of brain • Flat forehead and face • Less heavily developed jaws and small teeth

49. Homo sapiens sapiens

50. Homo sapiens sapiens Many advancements in art, culture and tool making technology