I think "lines" tend to develop around GOOD DOGS ... at least that is how it should be
In other words, when a truly great dog pops up, you're going to see (smart) people breeding around that dog and developing a line out of it.
Unfortunately, a lot of "pure dogfighters" (who buy dogs) don't have the sense to do this ... and let truly great genetic potential slip away.
...
Every woman I have ever been with has eventually gotten jealous of the attention I paid to my dogs, without exception.
And they also got jealous of the fact every dog we had just seemed to "love me more" than her ... which, of course, goes back to the attention I pay to my dogs compared to most "normal" people
Jack