Will old corn meal ruin muffins? I have found a recipe for muffins that I'd like to make, and it calls for corn meal. I found some in the pantry, but I don't know when it was purchased. It doesn't smell like much, just kinda like corn.

It might be pretty old. Possibly years. Will it ruin the muffins? Would the muffins be significantly better if I bought some new corn meal from the grocer?
If it is stale or rancid, you will get substandard muffins that simply don't taste very good.  Usually you would smell rancidity.

It is unlikely to have suffered mold or other decay if it still smells just like corn, but....  cornmeal is quite inexpensive, at least in the US.  You might want to buy a new bag.