So what can we safely speculate about the dominant species, some 50m years after humanity? The answer is both dissatisfying and thrilling all at once: while we can be reasonably confident that it won’t be a talking chimpanzee, we otherwise have no idea what it will look like.
The world has seen a number of mass extinction events in the course of its history. The diversification of life following each event was relatively rapid – and the “adaptive radiation” of new species produced new forms including many unlike the ancestral lineages that spawned them after surviving the prior extinction. The small shrew-like creatures that scurried beneath the feet of dinosaurs in the late Cretaceous period looked very different to the cave bears, mastodons and whales which descended from them during the age of mammals. Likewise, the reptiles that survived the late Permian extinction some 250m years ago, which killed off 90% of marine and 70% of terrestrial species did not clearly foreshadow the pterosaurs and dinosaurs and mammals and birds that descended from them.
In Wonderful Life: the Burgess Shale and the Nature of History, the late Stephen J. Gould argued that chance, or contingency, as he called it, played a great role during the major transitions of animal life. There is room to argue about the relative importance of contingency in the history of life, which remains a controversial subject today. However Gould’s insight that we can hardly foreshadow the success of modern lineages beyond a future extinction is a humbling reminder of the complexity of evolutionary transitions.
So while it may be possible that, as many have speculated, the ants will take over the Earth from us, we can only imagine what their dominant ant descendants will look like.