Sometimes it is possible to trace back street dance styles that were mostly pioneered by specific persons. One example is Locking, which is often regarded as being started by Don Campbell, who was a 1970s pioneer of American street dance. Most of the time it is impossible to credit specific people for street dances, since the dances evolve outside of professional dance environments, whereby there is no social and/or legal record. Street/vernacular dance pioneers also rarely have professional degrees in dance, thus distinguishing street dance from other modern dance forms.