Evolution isn't necessarily a process of "improvement"
Evolution generally follows a principle of adaptability for a certain environment. For example, a Cheetah is highly adapted for speed at the expense of agility, strength and size when compared to a Leopard.

You only need compare modern man with Neanderthal man, with whom we shared a common ancestor. Neanderthals were physically much more hardy and had bigger brains that humans. So why did they die out and we proliferate?

The counterweight to any arguement that evolution is about superiority can be expressed in two words - "Peter" and "Andre".
(Bicycle Repairman "you're also a bit of a wanker", Thu 17 Jul 2008, 10:05, Reply)