Jazz's first soloists were a church full of strangers
One musician liked to claim he invented jazz outright — the real ancestor of improvisation has no single name attached to it at all.
Jelly Roll Morton spent much of his career insisting he'd invented jazz personally. Historians studying the music's roots in the American South found something with no inventor at all: congregations reworking European hymns into a style of singing nobody had composed in advance.
Each voice varied the melody at its own pitch and its own timing, listening to the others and adjusting in real time, so the sound built into overlapping layers nobody had planned and everybody had made. Observers who tried to write it down on a musical staff mostly gave up — the notation kept failing to hold something that was never meant to sit still.
That's the actual ancestor of the jazz solo: not a lone virtuoso breaking away from the group, but a group that had already spent generations learning how to invent together before the word "jazz" existed to describe it.
The soloist came later, and got all the credit. The listening came first, and got none.