Rationalist
Hail Voltaire
common descent is nothing more than your assumed explanation.......there is no more evidence to support your assumption than there is to support a belief we were created in a particular way for a reason.....
for example, you assume that because whales have fins they are evolved from legs.....it is equally logical to conclude they were created with fins.....
It's not an assumption. I don't care to explain it, since nothing we can say will change your mind. Feel free to read about it yourself...or remain ignorant if you wish.
http://en.wikipedia.org/wiki/Evolution_of_cetaceans