  We study the evolution of an evaporating rotating black hole, described by
the Kerr metric, which is emitting either solely massless scalar particles or a
mixture of massless scalar and nonzero spin particles. Allowing the hole to
radiate scalar particles increases the mass loss rate and decreases the angular
momentum loss rate relative to a black hole which is radiating nonzero spin
particles. The presence of scalar radiation can cause the evaporating hole to
asymptotically approach a state which is described by a nonzero value of $a_*
\equiv a / M$. This is contrary to the conventional view of black hole
evaporation, wherein all black holes spin down more rapidly than they lose
mass. A hole emitting solely scalar radiation will approach a final asymptotic
state described by $a_* \simeq 0.555$. A black hole that is emitting scalar
particles and a canonical set of nonzero spin particles (3 species of
neutrinos, a single photon species, and a single graviton species) will
asymptotically approach a nonzero value of $a_*$ only if there are at least 32
massless scalar fields. We also calculate the lifetime of a primordial black
hole that formed with a value of the rotation parameter $a_{*}$, the minimum
initial mass of a primordial black hole that is seen today with a rotation
parameter $a_{*}$, and the entropy of a black hole that is emitting scalar or
higher spin particles.
