Short answers, pulled from the story.
Paul Tutmarc invented the first solid-body electric bass guitar in 1935. He created the Model 736 Bass Fiddle in Seattle, Washington, which featured four strings and a single pickup. Fewer than one hundred of these instruments were ever built.
Leo Fender and George Fullton began mass-producing the modern bass guitar in October 1951. They introduced the Precision Bass, which used a simple slab body and a single coil pickup to amplify sound electronically. This instrument replaced the double bass in popular music by 1957.
Alembic established the boutique electric bass guitar market in 1972. The company created custom-tailored instruments featuring unique designs and premium hand-finished wood bodies. Musicians like Phil Lesh, Jack Casady, and Stanley Clarke used these instruments with innovative construction techniques.
The first commercial fretless bass guitar appeared in 1966. The Ampeg AUB-1 was introduced that year to allow for a more vocal, sliding sound that mimicked the double bass. This design contrasted with the precise, staccato nature of fretted basses.
Bassist Anthony Jackson commissioned the first six-string bass guitar in 1975. He asked luthier Carl Thompson to build an instrument tuned B0, E1, A1, D2, G2, C3. This design added a low B string and a high C string to the standard four-string configuration.