Why do chickens lie eggs and not give birth like other animals?

Question: Why do chickens lie eggs and not give birth like other animals?
- Keywords:
  animal,
  birth,
  chicken,
  egg
Asked by laughinglils to Sam on 22 Jun 2011.
- Sam Tazzyman answered on 22 Jun 2011:
  
  Chickens are birds, and all birds lay eggs. This is because they evolved from dinosaurs, which also laid eggs. In fact, lots of species lay eggs – it’s only mammals like us that have live birth. I don’t know why live birth evolved in mammals though.

Question: Why do chickens lie eggs and not give birth like other animals?