Wade,

There is no definitive Catholic position on this. Some saints believed in a young Earth, some in an old Earth. Generally, though, today, the old Earth/theistic Evolution theory is most common belief.

As for Mark 10:3-9, I don't know what Moses and divorce has to do with the age of the Earth. Looks to me like he thinks that the existence of Moses, Noah, and Jonah somehow proves a young Earth but I don't see how; if the earth were 4.543 billion years old when Adam came on the scene, nothing prevents Noah, Jonah, and Moses from appearing after him.

As for how it can be that animals killed each other before Adam, that's an excellent question; the standard answer to which is that death entered the world only for man, not for man and beast.

Another point is that Genesis is not to be taken strictly literally but simply as an explanation of how man fell, and to convey theological truths in language the Hebrews would understand — not as a scientific treatise.

The problem with young Earth creationism is that there is too much scientific proof of the age of the universe. To make it work would require that God had deceived us, but God can neither deceive nor be deceived.

Eric