The size of the Ark is a well documented item in the bible. If you work out how big the Ark was, it turns out to be roughly the size of 2 - 3 foot ball fields. 16 million beetles would take a pretty good percentage of that space I think. Would become very crowded very quickly, and holy crap don't squash one on accident, you would have just caused that species to become extinct, thus failing in the purpose of the Ark to start with.
Why would I use the beetle as an example... Because thats how many species of beetle there are on the planet right now.
http://en.wikipedia.org/wiki/Beetle
I believe that there is a yen yang to it all. Such as there is to everything else in the universe. Evolution coupled with creationism. Not only one or the other, but both. If you were to say only one or the other, then you leave yourself with questions that will not pass logic tests on either side.