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 A105 Human Origins and Prehistory
A105 Questions over Life in the Trees

1.  What ways does the film discuss that prosimians communicate?  Why is communication important?

     Prosimians mainly communicate through scent and sound.  Using scent glands on their wrists and under their tails, they mark their territory and use scent in displays to other group memebers.  Some species are also known to use urine as a scent marker.  The indri, which is a highly arboreal animal, relies more on sound to communicate, using loud calls; perhaps this is because scent markings would be easily dispersed in the treetops.  Some lemurs such as the ringtailed lemur use visual signals -- waving their tails to keep the group together -- though this is less important for them than is scent.
      Communication serves to keep the group together when traveling, to mark a group's territory, to attract prospective mates, and to help in dominance interactions.

2.  Why might these animals have evolved grasping hands?  How are they useful to adults and infants?

     Grasping hands might have been selected for because they make locomotion in the trees much easier.  Such hands also aid in feeding on foods such as fruits and insects, as well as in grooming.  Adults use their hands for these purposes; infants use their grasping hands to grab on to their parents, as they are not left in the nest but rather spend all their time with the parents. 

3.  What might be an advantage to large body size? A disadvantage? How do some South American monkeys cope with being large and arboreal?

  Being larger makes it more likely that a male will win fights and be able to mate with females.  Of course, this then produces larger infants.  Larger animals may also be less vulnerable to predators, though this is less of a concern for primates.  A disadvantage to being a large tree-living animal is that the best foods (ripe fruit and new leaves) are at the end of branches, which may break under a large animal's weight.  Some New World monkeys have adapted to this by evolving a grasping (prehensile) tail, which gives them more support and allows them to distribute their weight more.