Complex sentence: It has been used as a healing ritual in the influence of fertility, birth, sickness, and death, since earliest human history but, the establishment of dance as a therapy and as a profession occurred in the 1950s.
Split into simpler sentences: It has been used as a healing ritual in the influence of fertility, birth, sickness, and death since early human history. The actual establishment of dance as a therapy and as a profession occurred in the 1950s.