The evolutionary history of five ancestral proboscidean (elephant-like) genera is illustrated in the graph below, showing their duration of existence in the fossil record and their estimated shoulder heights.
Which of the following is a valid, scientifically sound conclusion that can be drawn directly from the data presented in this graph?
Natural selection favored a larger shoulder height over time because larger sizes provided a selective advantage against apex predators.
There is no clear correlation between when a genus first appeared in the fossil record and its estimated shoulder height range.
Genera that first appeared more recently in the fossil record generally possessed larger estimated shoulder heights.
The extinction of Palaeomastodon was directly caused by competitive exclusion as Gomphotherium evolved larger body sizes.