ANTHROP 1AA3 Chapter Notes - Chapter 6: Foramen Magnum, Reverend Lovejoy, Paleoanthropology
14 Sep 2016
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Humans and the Environment
• The characteristic of bipedalism separates hominids from other primates and identifies them as a distinct
family
• Hominids are the closest fossil relatives of modern humans
• Genus homo evolved from the australopithecine
Trends in Hominid Evolution
• Hominids are members of the order of primates, likewise they share the basic primate characteristics
• Distinctive features of hominids include: reduction of face, jaw and anterior teeth and an inceased
cranial capacity
• Certain physical, cultural and social characteristics cannot be traced through fossil remains rather
anthropologists use early homins tools, food remains and living sites
Bipedalism
• Paleoanthropologists focus on the foramen magnum which is the opening in the base of the skull
through which the spinal cord passes
• In quadrupedal animals, this aperture is located at the back of the skull which allows the head to extend
out in front of the body
• In contrast, the foramen magnum in bipedal creatures is located on the bottom of the skull sitting
squarely above the body
• Bipedalism probably evolved due to a confluence of factors rather than a single adaptive characteristic
and it freed their hands to use tools, transport food and carry infants
Tool Use
• Use of tools would have given them a greater variety of food sources thus increasing survival and
reproductive success
• However, this is not the reason for bipedalism as tool making dates just over 2.5 million years but
bipedalism dates around 6 million years
Transport of food and offspring
• Bipedalism seems to be outweighed by the inabilitt to move quickly through the trees to avoid predators
• The added potential of dropping an infant would further reduce any possible adaptive advantage
• Transport of food does not seem likely since animals tend to eat their food source immediately when
found
• Any advantage of bipedalism in the field of infant or food transportation is offset by slower, less mobile
movement that would not have afforded an effective means of avoiding predators
Provisioning
• Because bipedalism involved the modifications of a wide range of biological and behavioural traits, it
must have conferred some adaptive advantage on early hominids, even before they had fully developed
the physical capabilities for bipedalism
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• Paleoanthropologist Owen Lovejoy posits that the crucial advantage may have been the ability to
transport food back to a mate by walking upright and using simple implements (ie. Broad leaves) to
maximize the amount of food that could be carried
• Provisioning by the male would have allowed the female to increase the quantity and quality of time
devoted to infant care
• This intensification of parental attention, would promote the survival of the infant and thus the species
• Lovejoy asserts that food sharing and cooperation may have produced a reproductive strategy tht
favoured sexual fidelity and close long-term relations between a male and a female
• A major criticism of Lovejoy's theory is that there is no evidence that early hominids favored sexual
fidelity or close, long term male-female relationships
Thermoregulation Models
• Food resources and selection were scattered and would have favoured endurance over speed in
locomotion
• Sweat glands and less body hair may have been selected for in hominids, traits which are readily
apparent in modern humans
• Bipedalism may have caused the early hominids to move slower over short distances but it would have
allowed them to move efficiently over longer distances thus allowing them to travel greater distances in
search of food
Reduction of the face, jaws and teeth
• The oldest fossil homiids have a protruding, progmathic, face, the jaw extending out further than in
humans as well as canine teeth larger than humans
• To accommodate these larger canines which extends beyond the other teeth, there are gaps between
the teeth of the opposing jaw. This feature is called diastema and is absent in humans
• The teeth in early hominids are arranged in a U-shaped pattern and the teeth on opposite sides of the
mouth are parallel. However, in humans jaw the teeth are not parallel but flare away from eachother
at the back of the mouth
• Some australopithecine fossil specimens have a sagittal crest, a bony ridge along the top of the skull
that grows larger as more chewing muscles reach up along the midline of the cranium
Increase in Cranial Capacity
• Before 2 million years ago, the size and organization of the hominid brain underwent comparatively
little change
Fossil Evidence for Hominid Evolution
• Ardipithecus Ramidus
o Ground ape at the root
o Very primitive
o Small/apelike cranial capacity
o Large canine teeth
o Bipedal
• Australopithecus Afarensis
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