http://malcolmsscifi.blogspot.com.au/2014/08/two-intelligent-species.html

An interesting if brief survey of (part of) one of my favorite questions…which has two parts:

1. Why are there formally representational intelligent animals on Earth? (might there be some kind of purposive vector in planetary evolutions that tends to produce them?)

2. Why is there only one species of formally representational animal on Earth (at this time)?