1. How We Study Hominid Evolution

2. Review of Taxonomy Linneaus: Binomial Nomenclature
Genus and species (Homo sapiens)
Also higher order taxa (categories)
Each category implies a similar type of adaptation (remember what that means?)

3. The Family Hominidae (Hominids)
Humans & our most recent ancestors
Primary Characteristic – “obligate” bipedalism
As they evolved – increased brain to body ratio

4. The Family Hominidae (Hominids)
Consists of multiple genera
We will focus on three:
Ardipithecus
Australopithecus
Homo

5. Ardipithecus
1 species we will study: - Ardipithecus ramidus

6. Australopithecus
4 species we will study: - Australopithecus afarensis - Australopithecus africanus - Australopithecus boisei - Australopithecus robustus

7. Homo - Homo habilis - Homo erectus - Homo sapiens
3 species we will study:
- Homo habilis
- Homo erectus
- Homo sapiens

8. Species Definitions Biological species
can mate and produce offspring that are capable of reproducing
But what if the species are extinct?
Morphological species
Distinguished on the basis of their morphological features (which reflect their environmental adaptations)

9. We will thereby be considering how each species behaved
So…
We will be looking at the various hominids primarily with respect to their morphology
But since form is related to function…
We will thereby be considering how each species behaved

10. Mosaic Evolution
Different parts of an organism evolves at different times and different rates
Homeobox (control) genes
Control one suite of traits but have little or no effect on others
SRY (sex Determining region y) gene (located from base pair 2,786,854 to base pair 2,787,740 on the Y chromosome)

11. Three Parts of Our Mosaic Evolution
cranial capacity
the dentition & chewing apparatus
the bipedal adaptation

12. Cranial Capacity interior volume of brain case
measured in cubic centimeters (cc or cm3)
approximate estimate of brain size

13. Definitions: Cranium Cranial: Bones of the skull
Foramen magnum: where spinal cord enters brain cavity

14. Dentition/Jaw 2:1:2:3 dental formula Diastema: gap in teeth
Figure 11.10a

15. Dental Arcade
Shape of jaw
U-shaped
Parabolic
Figure 11.10a

16. Dentition/Jaw
Simian shelf: buttress of bone under lower incisors (supports jaw in chewing)
Sagittal crest: ridge of bone at tone of skull where muscles for mastication attach

17. The central adaptation of the Hominids
Bipedalism
The central adaptation of the Hominids

18. Figure 05.17

19. Figure 05.19d

20. Figure 05.20

21. Cranial Indication of Bipedalism
position of foramen magnum

22. Figure 05.27
Why Bipedalism?

23. The “radiator” hypothesis
Figure 11.33
The “radiator” hypothesis
Bipedal locomotion helps an animal living in warm climates to keep cool by reducing the amount of sunlight that falls on the body, by increasing the animal’s exposure to air movements, and by immersing it in lower-temperature air.
Why Bipedalism?

24. The Study of Hominids Is the study of our own lineage
Subject to emotional interpretation
Conscious and unconscious biases

25. Questions, Questions What drove the changes leading to humans?
Was there a “prime mover”?
What makes us human?
What anatomical aspects of ourselves truly set us apart from other animals?

26. The Lesson of Piltdown
1912
Skull (large brain)
Jaw ( ape-like)

27. The Piltdown Hoax
FRAUD!
Human Skull
Orangutan jaw

28. Lessons of The Lessons of Piltdown
Fluorine analysis is a useful dating method
Let fossils speak for themselves!

29. Figure 05.32a

30. Figure 10.18
The tree in (a) shows the complete phylogeny of a hypothetical lineage, and the tree in (b) shows the same phylogeny when only a small percentage of the fossil species have been discovered. The red lines show the species that have been discovered, and the gray lines show the missing species. Note that all living species are known, but only 3% of the fossil species have been discovered. (c) The tree we would have to infer from the incomplete data at hand differs from the actual tree in two respects: 1) it links each species to its closest known ancestor, which often means assigning inappropriate ancestors to fossil and modern species; and 2) it frequently underestimates the age of the oldest member of a clade.