How can I find the first researcher who wrote about a specific subject I am writing my thesis in computer science and I am looking to include some references. I need to include though the researchers who first wrote about a specific subject and not others who expanded the original ideas.

I use Google Scholar for searches but there isn't an option to search for this criteria.

How can I find the first researcher who wrote about a specific subject?
I'm a little unclear about why you might want the very first, but at least in CS you have a limited history to work with. 

The most detailed way to find this is to start with current papers (maybe a good review article) on the subject and to track back the references until you find the first one, paper-by-paper. If you already have a few early papers, obviously looking at their references is a better place to start. You haven't given us the topic area, but you might just ask for the earliest papers on the CS Theory Stackexchange. You might also try searching on Google by year if you are certain that you know the right keywords--binary searching the years back to 1900 or so will probably be most efficient.

Finding the right paper might be a little challenging, especially if the topic has changed names a few times since it started.

Edited to add: If you are at a university with a good library system, you might find a research librarian who does this kind of thing for a living and ask them for help.