Evo-Devo

I have always found people's inherent desire to know where we came from fascinating.  I went to a Catholic grade school and high school and was never taught much about evolution.  I am agnostic and always thought it was funny to have adults teaching me that God decided to spend a week creating the earth and we are all descendants of the same two people, one of which was made from the rib of the other.  This all seemed pretty ridiculous to me.  

Darwinism:

The idea of Darwinism makes sense.  I'm not sure exactly what it means for me personally.  I guess if I had a certain gene that prevented me from getting cancer, and I passed it on to my children and so on, it would be Darwinism at work.  

I find it a little strange that we use this idea to our advantage sometimes.  Dog breeders will only breed 2 dogs that have certain desirable characteristics, or scientists will combine plants with certain immunities to bugs or fungus.  I guess my question is just like previous questions I've asked in this blog.  If we are going to play God, how far should we be allowed to take it?