The gradual migration of a herd of elephants into new territory due to a shortage of water and food in their original habitat
An increase in prehensile taft strength after a species of monkeys began living among taller trees to avoid terrestrial predators
The sudden extinction of a breed of wild donkeys following a dramatic change in climate
The discovery of prehistoric fossils demonstrating the existence of a creature with both mammalian and amphibious characteristics
The discovery of a previously unknown species of crocodile in waters traditionally considered too cold for reptiles