Of course a person can be both scientist and theologian, however, I doubt if this hypothetical person could get a scientific article published in a peer-reviewed journal containing theology as part of the discussion (let's exclude archeology from this hypothetical arguement). 
I do not believe theology is a science. It does not use the tools of science and is adverse to evolving theory. Strange how often a theological/ethical argument concludes something that is factually not true. I can think of a couple of example:
- homosexuality is a natural orientation in many species
- overpopulation stresses the resources of our planet resulting in wars, famine, disease and environmental decay
How does theology use these facts?
Having said this I consider myself Catholic basing my personal ethics on my religious beliefs.