What is the likely hood of a second intelligent species evolving?

Question: What is the likely hood of a second intelligent species evolving?
- Keywords:
  evolution,
  evolve,
  human,
  intelligence,
  intelligent
Asked by neil3rd to Chris on 20 Jun 2011.
- Christopher Phillips answered on 20 Jun 2011:
  
  We already have plenty of intelligent speices here on the Earth 🙂
  Cats, dogs, whales, dolphins, monkeys, apes, tons and tons!
  some of them are even smarter than most humans it would seem 😉

Question: What is the likely hood of a second intelligent species evolving?