Chapter 10- Hominid Origins
Terms
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- Pertaining to the Pliocene and first half of the Pleistocene, a time range of 5-1 m.y.a. For this time period, the earliest fossil hominids have been found in Africa.
- Pilo-Pleistocene
- Pertaining to the form and structure of organisms.
- Morphological
- The opening at the base of the skull through which the spinal cord passes as it enters the body to descend through the vertebral column. In quadrupeds, it is located more to the rear of the skull, while in bipeds, it is located farther beneath the skull.
- Foramen magnum
- An early hominid genus, known from the Plio-Pleistocene of Africa, characterized by bipedal locomotion, a relatively small brain, and large back teeth.
- Australopithecus
- Adapted for cutting or shearing; among primates, refers to the compressed (side-to-side) first lower premolar, which functions as a shearing surface with the upper canine.
- Sectorial
- The colloquial name for members of the genus Australopithecus. The term was first used as a subfamily designation, but it is now commonly used informally.
- Australopithecine
- Raised ridge along the midline of the cranium where the temporal muscle (which closes the jaw) is attached.
- Sagittal crest
- A species of early Homo, well known from East Africa but perhaps also found in other regions.
- Homo habilis
- A solid impression of the inside of the skull, often preserving details relating to the size and surface features of the brain.
- Endocast
- A schematic representation showing ancestor-descendant relationships, usually in a chronological framework.
- Phylogeny
- _________ is the earliest hominid at present with substantial definite supporting evidence.
- A. Afarensis
- _________ is probably ancestral to all later hominids (or is very closely related to the species that is).
- A. Afarensis
- _________ is ancestral solely to the "robust" group (clade), linking it with earlier afarensis as well as with one (or both) later robust species.
- A. Aethiopicus
- All ____________ were extinct by 1 m.y.a. (or shortly before).
- australopithecines
- T or F: All australopithecine species (presumably early Homo as well) were highly variable, showing extreme sexual dimorphism.
- True
- T or F: Since there is so much intraspecific variation, on average there was not much difference in body size among australopithecine species.
- True
- _______ was probably not the last common ancestor of the robust lineage and genus Homo. That is, phylogeny C is probably not entirely correct.
- A. Africanus
- T or F: Most forms (including some members of early Homo) had large back teeth.
- True
- There was substantial __________ (__________) in physical traits among early hominid lineages.
- parallelism (homoplasy)
- T or F: Given the current state of knowledge, there are several equally supportable phylogenies.
- True
- What other modifications occurred as a result of bipedalism?
-
1) repositioning of foramen magnum
2) addition of spinal curves that faciltate weight transmission
3) shortening and broadening of the pelvis and stabilization of weigh transmission
4) lengthening of the hind limb, thus increasing stride length
5) angling of the femur inward to bring the knees and fee closer together under the body
6) development of a longitudinal arch and realignment of the big toe in parallel with the other toes - T or F: Hominid bipedalism is habitual and obligate, with habitual meaning hominids moving bipedally as their standard and most efficient mode of locomotion, and obligate by hominids committed to bipedalism and cannot locomote efficiently in any other ma
- True