Background: Michael Anthony Sobolewski (born June 20, 1954 and legally shortened his name to Michael Anthony in 1978), is an American musician who is currently the bass player in the rock supergroup Chickenfoot and the Circle. Anthony is best known as the former bass player for the hard rock band Van Halen. Anthony is known for his stage antics, his effects-laden live solos, his number of custom-made bass guitars, including a Jack Daniel's model shaped like a whiskey bottle, and his background vocals in Van Halen. He also has a signature Schecter Guitar Research bass-guitar series.
Context: While Anthony was a promising catcher in baseball, he also competed on the Dana Junior High School track team (long jump) and played in the marching band there from 1967-1969. He took an interest in guitar as a teenager, but picked up the bass instead since most of his other friends already played guitar or drums. Anthony's friend Mike Hershey gave him a Fender Mustang electric guitar that Anthony converted by removing the two highest strings and playing it as a bass guitar. Eventually, his father bought him a Victoria copy of a Fender Precision Bass and a Gibson amplifier. Anthony mostly modelled his bass playing after Jack Bruce of Cream, but also admired Led Zeppelin's John Paul Jones and Harvey Brooks of Electric Flag. His first band was called Poverty's Children. Other bands he played in included Black Opal, Balls, and Snake. Although Anthony is naturally left-handed, he plays right-handed.  Snake, a three-piece group featuring Anthony on lead vocals and bass guitar, was the last band in which Anthony played before joining Van Halen. Snake played covers of ZZ Top, Lynyrd Skynyrd, and Foghat, along with some original songs. They played several of the same types of gigs as did the Van Halen brothers' band Mammoth. Snake even once opened for Mammoth at a show at Pasadena High School. Mammoth's PA failed that night, so Anthony lent them Snake's PA.  While attending Pasadena City College, Anthony pursued a degree in music. Eddie Van Halen also took classes there and they would often see each other on campus. During this time, bass player Mark Stone parted ways with Mammoth and the Van Halens decided to audition Anthony as a replacement. Anthony was impressed by their skill during subsequent jam sessions even though he had seen the brothers play before. After the session, the Van Halen brothers asked Anthony to join their band. One story claims that he said he had to think about it and consulted Snake guitarist Tony Caggiano who advised Anthony to join Van Halen. However, according to Michael Anthony's web site, when asked if he wanted to join Mammoth, Anthony immediately said yes. This has become the accepted version of events.
Question: How did his career start?

Answer:
played in the marching band there from 1967-1969.