Introduction to Hominid Evolution

How We Study Hominid Evolution
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?)
The Family Hominidae
• Humans & our most recent ancestors
• Primary Characteristic – “obligate” bipedalism
• As they evolved – increased brain to body ratio
The Family Hominidae
• Consists of multiple genera
• We will focus on three:
 Ardipithecus
 Australopithecus
 Homo
1 species we will study:
- Ardipithecus ramidus
4 species we will study:
- Australopithecus afarensis
- Australopithecus africanus
- Australopithecus boisei
- Australopithecus robustus
3 species we will study:
- Homo habilis
- Homo erectus
- Homo sapiens
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)
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
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)
Three Parts of Our Mosaic Evolution
• cranial capacity
• the dentition & chewing apparatus
• the bipedal adaptation
Cranial Capacity
• interior volume of brain
• measured in cubic
centimeters (cc or cm3)
• approximate estimate
of brain size
Definitions: Cranium
• Cranial: Bones of the skull
• Foramen magnum: where spinal cord enters
brain cavity
• 2:1:2:3 dental formula
• Diastema: gap in teeth
Figure 11.10a
Dental Arcade
Shape of jaw
Figure 11.10a
• 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
The central adaptation of the Hominids
Figure 05.17
Figure 05.19d
Figure 05.20
Cranial Indication of Bipedalism
position of foramen magnum
Figure 05.27
Why Bipedalism?
The “radiator” hypothesis
Figure 11.33
Why Bipedalism?
The Study of Hominids
• Is the study of our own lineage
• Subject to emotional interpretation
• Conscious and unconscious biases
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?
The Lesson of Piltdown
• 1912
• Skull (large brain)
• Jaw ( ape-like)
The Piltdown Hoax
• Human Skull
• Orangutan jaw
The Lessons of Piltdown
• Fluorine analysis is a
useful dating method
• Let fossils speak for
Figure 05.32a
Figure 10.18