THEME AND VARIATION
Classifying the Tree Shrew
In the forests of Borneo lives a small, furry, long tailed creature resembling a squirrel but called a Tree Shrew, (Tupaia glis). Unlike a squirrel this creature does not eat vegetable matter, but hunts small invertebrates. When first discovered its phylogenetic relationships with other animals was much debated and it was called a tree shrew based on its dental similarity (small, pointed unspecialized teeth) to insectivores. Some scientists suggested that the structure of its genitals indicated a relationship with marsupials, whereas others analysing the structure of its skull noted an exceptionally large brain, and proposed that it was a very distant ancestor of monkeys and apes. The debate is not over yet. Currently the balance of opinion has swung away from viewing the Tree Shrew as an ancestral monkey and favours classifying it within its own mammalian order (Scandentia) but recognizing that its closely allied to other primitive mammals such as shrews which are classified within the order Insectivora.