1. Early hominid origins and evolution: the roots of humanity
Chapter 7

2. Introduction
Charles Dawson found a fossil that he said was the “missing link”
It had a human skull and an ape jaw
Called Piltdown Man
It was a hoax (human skull fused with an orangutan jaw)
Shows people (wrongly) thought human ancestors were hybrid ape-men

3. What Separates Humans? It is not big brains It is bipedalism
We began walking bipedally 7 mya (million years ago)
We got big brains only 2 mya

4. Classification Please remember: Hominids are ancestors of any apes
Hominins are ancestors of humans

5. Pg. 194

6. bipedalism
Historically, scientists believed the identifiable feature of human ancestors was big brains
This was not supported in the fossil record
How would we tell bipedalism from a fossil?

7. Classification
Also remember that humans go in the ape classification of Hominoid
Why?

8. Classification
Also remember that humans go in the ape classification of Hominoid
Why?
Y-5 molar
No tail
Shared DNA

10. Bipedal adaptations 1. foramen magnum underneath skull
2. short, wide pelvis
3. long legs
4. no opposable big toe
5. double-curved spine

11. Bipedal adaptations

12. Other hominin features
Honing canine: apes’ canines cut and shred food and are large and dangerous and they have a diastema.
Humans have small, nonhoning canines and no diastema
Apes have powerful chewing muscles and a sagittal crest for extra power. Humans are weak chewers
Why? What invention did human ancestors have that made food processing easier?

13. Other hominin features

14. bipedalism
It is hypothesized that our ancestors were knuckle-walkers, which allowed for easier upright standing
Climate and environmental changes may have selected for bipedalism

16. Why did bipedalism evolve?
Darwin’s Hunting Hypothesis: because of similarities between humans and apes, he concluded Africa must be our origin. There must have been something to shift us to walking on the ground
Unique human traits:
Bipedal vs quadrupedal
Tiny canines vs large canines
Tool use vs no tool use
Big brains vs smaller brains

17. Why did bipedalism evolve?
Darwin’s Hunting Hypothesis: Darwin asked what advantages bipedalism had and he concluded it freed the hands for holding weapons
We now know that we walked many millions of years before tools were made, but his hypothesis laid the foundation

18. Why did hominins evolve?
Another hypothesis involved the forest becoming fragmented, and hominids walking on two legs in between patches of trees.
Used less energy
Could see predators
Could hold things with hands
Less of the body in direct sunlight

19. Why did hominins evolve?
Owen Lovejoy’s Provisioning Hypothesis: heavy parental investment by mothers led to bipedalism
Males would better provision females if bipedal (free hands to carry more food)
Better infant survival and higher fitness for mother
Small level of sexual dimorphism in fossils supports this (cooperation of male and female pair…not males fighting for one female)

21. Benefits and costs of bipedalism
Pros:
Can carry things (frees hands)
Can see predators
Can save energy
Cons:
We are slow
If carrying items, makes us easy targets
Back injuries
If injure a foot, very difficult to get around

22. Who were the first hominids?
Pre-Australopithecines
Australopithecines
Paranthropus

23. Early hominins in east africca
Rift Valley
Volcanic rock
What dating technique?

24. Pre-australopithecines
Sahelanthropus tchadensis: earliest ancestor/oldest biped
“Chad Man”
7-6 mya
Central Africa (Chad)
Small brain (350 cubic cm, cc)
Bipedal (foramen magnum)
Nonhoning canine
Close to the divergence of human line from ape line

25. Pre-australopithecines
Sahelanthropus tchadensis

26. Pre-australopithecines
Orrorin tugenensis:
“Original Man”
6 mya
Mostly femurs (thigh bone)
Show bipedalism
Nonhoning canines

27. Pre-australopithecines
Aridpithecus ramidus:
“Great-grandma”
“Ardi”
4-6 mya
Bipedal
All species so far still spent time in the trees…why?
May be direct ancestor to Australopithecines

28. Pre-australopithecines
Aridpithecus ramidus:

29. australopithecines Australopithecines:
Hundreds of fossils from at least 7 species
Not 100% sure of all the relationships

30. australopithecines Australopithecus africanus:
Raymond Dart found a small skull in a cave
“Taung Baby”
4-3 mya
Thought baby ape at 1st
Small teeth, bidpedal foramen magnum
Later adult fossils had small canines too
*Showed that bipedalism came way before big brains*

31. australopithecines
Australopithecus africanus:

32. australopithecines Australopithecus afarensis: Kenya and ethiopia
3 mya
Best-known and best-represented
“Lucy” over 40% of skeleton (but over 80% because skeleton is symmetrical)
If Ardi is great-grandma, Lucy is grandma
Foramen magnum, pelvis, legs, and feet all bipedal
Curved fingers (why?)
Small brain still (430 cc)

33. australopithecines Australopithecus afarensis: Smaller canines
Laetoli Prints: fossilized footprints in volcanic ash (how would you date these??)
Showed bipedalism and ‘first family’ (2 adults, 1 child)

34. australopithecines
Australopithecus afarensis:

35. australopithecines
Australopithecus:

36. australopithecines
Beginning 3mya, two lines of hominin evolution occurred, each with unique adaptations
One line went extinct and one line led to genus Homo

37. paranthropus This next group is the second line that went extinct
Some still call this group “robust” Australopithecus but there are enough differences that I split them into a new genus Paranthropus
Paranthropus:
2.5 mya
Larger, more robust bodies but small brains
Sagittal crest
Huge molars for crushing tough food
Flaring face
Do we have these adaptations?
Specialized food source may have led to extinction

38. paranthropus
Paranthropus:

39. Differences Biped Slender Small brain Rounder head Smaller teeth
AUSTRALOPITHECUS
PARANTHROPUS
Biped
Slender
Small brain
Rounder head
Smaller teeth
Varied diet
Biped
Robust
Small brain (smaller than A.)
Flared head
Sagittal crest
Large molars
Specializeed, tough diet

40. Pg. 197