What is the difference between 100% whole wheat pasta and 100% whole wheat couscous?
Other than the shape, obviously, not that much in the grand scheme of life.
the couscous grain is coarse wheat semolina; when wanting to eat it, it is usually boiled (boiling water added to couscous) or steamed (using a couscoussière)
Pasta is a dough made from finer semolina, it is made with water or eggs.
From the pasta dough, you can make many different type of pasta.
Some small pasta shape can look like couscous, for example Kushku or Fregola (larger than normal couscous) ...
As to know which came first, I would venture to say Couscous as it is easier to prepare.