And they were also a sort of skill:
Str+Dex: leap, somersault
Str+Int: lift or bend
Str+Chr: flex or flaunt
Dex+Chr: dance, sing, act
Suppose further that you grafted on (in order to get a skill check mechanic out of these 15 abilities) the Ghostbusters (or Risus) system by treating each full 6 points of an ability score as one die to roll to match the Target Number assigned by the Ghostmaster or referee--that is, 3-5 (+0), 6-11(+1), 12-17(+2), 18(+3). That distribution isn't very good. I'll have to sit down and look at the numbers with a Mathmagician friend.
Why, then they you'd be on your way to playing D&D the way we do on The Mutant Earth.