Quiz 7 Flashcards
Give the genus names of two fossil species that are considered potential ancestors of australopithecines. Briefly describe one form of anatomical evidence from any one of these specimens that has been used to suggest that they might be hominin ancestors.
2 fossil species that preceded the australopithecines - ardipithecus and sahelanthropus
Ardipithecus are considered potential ancestors of australopithecines because their molars are intermediate between chimpanzee and australopithecus teeth.
Describe two skeletal features found in australopithecines that indicate that they were habitual bipeds.
Two features that indicate the potentially bipedal nature of australopithecus locomotion are their extended free lumbar vertebrate and broad horizontal pelvis.
Describe two skeletal features found in australopithecines that indicate that they still retained arboreal adaptations.
Australopithecus feet have slightly divergent big toes, characteristic of brachiators, and long curved fingers. Their rib cages are also indicative of adaptations to suspensory motion.
Describe one method used to determine the geological age of a fossilized bone.
Radiometric dating can be useful when volcanic ash falls and leaves layers with distinctive ratios of potassium 40 and argon 40 isotopes. The decay of potassium into argon can indicate the age of the fossil.
What is one difference in the australopithecine trunk skeleton that is not seen in knuckle-walking apes?
Australopithecines have more “free” lumbar vertebrate (some species have 6)
What skull feature is both a correlate of bipedalism and of suspensory locomotion (i.e. brachiation)?
anterior foramen magnum
Describe how each of following skull structures in autralopithecines compare to great apes
a) sagittal ridge
b) zygomatic arch
c) teeth
d) position of foramen magnum
Sagittal ridge - APs have larger sagittal crests than apes.
Zygomatic arch - APs have larger and wider zygomatic arches.
Teeth - Australopithecines have reduced canines and diastema, and thicker molar enamel.
Foramen magnum position - more anterior than apes
What evidence suggests that australopithecines subsisted on a diet of mostly fibrous vegetable foods?
The more robust australopithecines had massive faces, large zygomatic arches and sagittal crests, reduced incisors/canines, and larger thick-enamel molars, all suggesting that they ate rough and fibrous foods.
When do the first stone tools appear in the fossil record?What is this sort of tool technology called?
What is the name of the site where the earliest stone tools have been found?Name a fossil species living at that time that is a likely producer/user of these tools.
The oldest stone tool technology, or Oldowan stone tools, first appeared in the fossil record around 2.5 MYBP and were found in Gona in Ethiopia. The species australopithecus garhi appeared to have used these tools at the time.
Did australopithecines use their canines for male-male competition, as do most other polygynous primates? Did they use them for predator defense? Explain.
It is unlikely that australopithecines used their canines for either of their purposes because their canines are reduced and much smaller than those of apes.
What large fossil great ape from South Asia is a member of the clade that includes the modern Orangutan? What other fossil species is from this same South Asian ape clade?
Sivapithecus is from the same lineage as orangutans, and Gigantopithecus is also a member of this clade.
Describe a feature of australopithecine teeth that
a) is not found in living apes but is found in modern humans.
b) is not found in humans and not found in any living primates.
a) reduced canine size
b) huge molars
When do the first stone tools appear in the fossil record?What is this sort of tool technology called?
What is the name of the site where the earliest stone tools have been found?Name a fossil species living at that time that is a likely producer/user of these tools.
The oldest stone tool technology, or Oldowan stone tools first appeared in the fossil record about 2.5 MYBP and were found in Gona in Ethiopia. There is evidence to suggest that the australopithecus garhi used these stone tools at the time.
What evidence suggests that australopithecines lived in polygynous social groups?
Australopithecines appeared to have been highly sexually dimorphic, based on the bimodal size distribution of jaw fragments that have been found. High levels of sexual dimorphism are usually associated with polygynous social structures.
