Horses are much larger today than their two-foot tall ancestor, mesohippus. geologists believe the change in size was the result of changing environments, from tropical forests to a grassland habitat. larger size would be an advantage for survival in this new habitat because a) taller horses could reach the leaves that grow high on trees. eliminate b) larger horses could find food easier than the shorter horses. c) the larger horses were better camouflaged than the smaller horses. d) larger horses had longer legs and could run faster to escape predators.