1. Evolution: On The Origin of Humans
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 freeing hands 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 ( )
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. Sahelanthropus tchadensis
7-6 mya in Chad (North Central Africa)
2. Orrorin tungenensis
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 ( 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. Ardipithecus ramidus
mya in Ethiopia (East Africa)
2. Australopithecus anamensis
mya in Kenya (East Africa)
Note: These organisms were forest adapted and fully bipedal.

15. Earliest True Hominid or Last Common Ancestor?
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
mya
Probably walked upright
Teeth enamel thicker than Ardipithecus ramidus, 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)

19. Mandible more chimpanzee-like while features of the tibia and humerus suggest bipedalism.

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
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
Lucy was named after the Beatles song “Lucy in the Sky with Diamonds” because that is what was playing on the radio the night the Leakey’s celebrated her find.

24. 2. Australopithecus africanus
4-2.5 mya in Transvaal region of South Africa
1924: 1st Australopithicine 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
best known A. africanus cranium (front & lateral views)
Australopithecus africanus
Most complete A. africanus skull
Taung Child

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

27. 3. Kenyanthropus platyops
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
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
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 Homo species

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. Average height = 3’4’’ to 4’5’’ Average weight = 70 lbs.
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. By this time, the feet of early humans had a modern-type arch
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 = lbs.
Skull shows that this individual lost their teeth sometime before their death indicating that they must have been cared for in order to survive.

43. Hand axe – first major innovation in stone tool technology
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. Used wooden spears to routinely hunt large animals
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.
Speculation abounds as to what interactions modern humans had with Neanderthals. Suggestions include: out competing, interbreeding, and defeat in battle
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. Many advancements in art, culture and tool making technology
Homo sapiens sapiens
Many advancements in art, culture and tool making technology

51. Map of Hominid Evolution
Facultative bipedalism refers to organisms that are capable of walking or running on two legs (usually for only short periods of time), but normally prefer quadripedal locomotion