Interesting. Of course the "Mohammadan Theory" was not a theory in the modern sense. Like I said other groups has similar speculations. What made Darwin's theory a theory is that it was testable. It offered an explanation of how evolution occurred. A modern scientific theory has to have a mechanism (in Darwin's case it was the combination of variation and natural selection) and it needs to be testable. Usually by the predictions that the concept can make.
There were quite a few "evolutionists" before Darwin. Here is just one article about that, none of them qualified as scientific theories:
Evolutionary Thought Before Darwin (Stanford Encyclopedia of Philosophy)
And your article was rather interesting. In the past Muslims led the world in the sciences for a while. That was when their religion was not overly oppressive. Drapers' purpose in citing that "theory" was an indictment of overly literal Christian religions.