FAST-TWITCH TOPHEAVY. “In other words, our minority of slow-twitch fibers was far greater than the minority of slow-twitch fibers in chimpanzees and macaques. The distribution of slow-twitch fibers in human is roughly 15–20%, whereas in chimpanzees and macaques it is only 2–7%.”
http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full