Unlike the widespread HIV-1 M strain, and the much rarer N and O strains, which jumped to people from chimpanzees, the newly described P strain originated in gorillas.
Steele, K. M. , T. N. Ball, and R. Runk, " Listening to Mozart does not enhance backwards digit span performance. " Percept Mot Skills, 1997. 84 (3 Pt 2): p. 1179-84.