Generally, the downside of having tissues grow / heal faster is increased growth rate of cancers. I'm speculating, but exposure of the skin to the sun's ultravi

Generally, the downside of having tissues grow / heal faster is increased growth rate of cancers. I'm speculating, but exposure of the skin to the sun's ultraviolet radiation may have helped determine the trade-off. Also, I would argue that there isn't a large selective pressure for skin to heal faster. Once a wound has scabbed over, the risk of infection is relatively low.