Question

5 In examining a number of mammal skeletons-for example, bear, lion, opossum, wolf, raccoon, pig, and elephant, in addition to several primate species-what characteristics would you use to decide whether a skeleton is a primate? Circle the characteristics in the following list that you would use to make your determination fur forward-facing eyes relatively large brain opposable thumbs mammary glands relatively small olfactory bulbs 6 For the characteristics you did not circle, why didn't you think they would be useful to differentiate primates from nonprimates? 7 Fill out this table using skulls in your labs collection (or substitute Fig. 9.3) Characteristic Dog Monkey or Ape Does it have a postorbital bar? Is cranium size (brain size) larger or smaller compared to size of face? Greater or less emphasis on olfaction, based on snout length? Do orbits face directly forward or somewhat lateraly? 8 An important primate feature is forward-facing eyes, which allows for depth perception. Close one eye, and then close the other eye before answering the following questions. a Draw a person's head from the top/superior view it could be just a simple circle), and fill in the location of the eyes. b Based on your range of vision after closing each eye, in your sketch draw lines from the eyes that show the ap proximate fields of vision for each eye (you will have two lines going out from each eyel. Shade in the area of overlap between the fields of vision. This is how depth perception is accomplished from overlapping visual fields 254 Exploring Physical Anthropology

Answer 1

5. Forward-facing eyes, relatively larger brain and opposable thumbs are the features which distinguish the primate skeletons from any other mammalian skeleton. The skull has cavities for eye balls and brain. The position of cavities for eye ball and larger cavity for brain in primates indicates that they have forward-facing eyes and larger brain respectively. The opposition of thumb can be identified by movement.

6. All mammals and primates have mammary glands in common, hence they cannot be used to distinguish between primates and mammals. Primates generally have hairs instead of fur and also they have relatively smaller olfactory bulbs than mammals. Eventhough fur and relatively smaller olfactory bulbs can distinguish between mammals and primates, they cannot be used to distinguish between them through skeletal structures.

7.

Characteristic	Dog	Monkey or ape
Does it have a postorbital bar	No	Yes
Is cranium size larger or smaller compared to face size	Smaller	Larger
Greater or less emphasis on olfaction, based on snout length	Greater	Lesser
Do orbits face directly forward or somewhat laterally?	Somewhat laterally	Directly forward