>>38199393This is likely the case. If you look at the list of pokemon by index number as well as the original sketches. Almost all of the first pokemon are the only ones of their lines. You have to go a good 80 pokemon in before you start seeing batches of evolutionary lines. It's possible that evolution was going to be very rare.
And when it was expanded, lines were either given new members or were combined into one. Graveler and Golem are both in that first batch, but 10 slots apart for each other. And Geodude is one of the last to be made.