Members of the horse family (Equidae) have evolved over millions of years.
What conclusion about horse evolution can be made from the graph?
Natural selection favored larger horses because they were faster and could escape predators more easily.
Modern horses (Equus) actively competed with Pliohippus, leading to the extinction of Pliohippus.
In general, the more recently a genus first appeared in the fossil record, the larger its body mass.
There is no clear correlation between estimated body mass and when a genus first appeared.