Right now, the orthodox scientific explanation for how different species arose is Evolution Theory. So-called "Intelligent Design" is NOT by any means, a proper scientific theory or even hypothesis. However, it does not follow that Evolution Theory is the ONLY possible explanation for the origin of life and its different forms.
The problems with those dolts propounding "intelligent design" is that not only they are a distraction from proper scientific inquiry but that they end up polarizing the debate. If someone asks me if I believe in "Evolution Theory" as a complete and satisfactory explanation for the structure of life forms and I say "no", does that mean then that I believe in the whole stupid unsupportable, untestable, improperly put-forth notion of "intelligent design"? OF COURSE NOT!!
There are some other theories which, while not currently accepted by mainstream science, seem to be put together well enough to merit at least some consideration.
One of these is the theory of "morphogenetic fields" advanced by Rupert Sheldrake and some others which have similar notions. This book: http://www.amazon.com/On-Origin-Form.../dp/1556438869 in particular, talks about alternative or supplemental theories to Darwin's theory of Evolution.
If the evangelicals stopped distracting us with their "intelligent design" noise bull$hit and allowed people to think deeply and clearly about the problem, then we may actually end up finding some real answers. The key thing here is not to be fooled by them into believing that it's got to be an either-or issue and to realize that there are many many other far more intelligent, educated and well-threshed out alternative theories than "God did it".