A better understanding of the evolution of horses.
WiYC asserted that Niles Eldredge 'refuted' horse evolution. Eldredge was arguing against the outdated idea of horses evolving in a straight line progression. Eldredge and other paleontologists would argue that the fossils point to a more complicated bushy tree of fossils with the only surviving member being the modern horse.
From the Horse Evolution FAQ on TalkOrigins:
"As new fossils were discovered, though, it became clear that the old model of horse evolution was a serious oversimplification. The ancestors of the modern horse were roughly what that series showed, and were clear evidence that evolution had occurred. But it was misleading to portray horse evolution in that smooth straight line, for two reasons:
1. First, horse evolution didn't proceed in a straight line. We now know of many other branches of horse evolution. Our familiar Equus is merely one twig on a once-flourishing bush of equine species. We only have the illusion of straight-line evolution because Equus is the only twig that survived. (See Gould's essay "Life's Little Joke" in Bully for Brontosaurus for more on this topic.)
2. Second, horse evolution was not smooth and gradual. Different traits evolved at different rates, didn't always evolve together, and occasionally reversed "direction". Also, horse species did not always come into being by gradual transformation ("anagenesis") of their ancestors; instead, sometimes new species "split off" from ancestors ("cladogenesis") and then co-existed with those ancestors for some time. Some species arose gradually, others suddenly.
Overall, the horse family demonstrates the diversity of evolutionary mechanisms, and it would be misleading -- and would be a real pity -- to reduce it to an oversimplified straight-line diagram."