[the OlLine Rebel]

But my point was that animal-fighting of all kinds was widespread prior to 1900. Hence, theoretically most of the "pits" used for pets were heavy on fighting lines.

If anything, now, the "pits" seem to be of 2 classes, altho I don't know for sure. (I'm assuming it's like the many splits in "German Shepherds" - basically, you're developing different breeds for the same origin thru "evolutionary" genetics following what you want.)

[LongElegantLegs]

But my point was that animal-fighting of all kinds was widespread prior to 1900. Hence, theoretically most of the "pits" used for pets were heavy on fighting lines.

That's true; Maybe they had more outlets for their aggressive instincts?