As the climate warms, conservationists have ever more to learn from paleontologists, who know a great deal about what sorts of species have managed to coexist in various ecosystems in the past (“Avoiding the Heffalump Trap,” October 3, 2009). Not surprisingly, the two are now contemplating assisted migration from Africa to North America. Moving the endangered lions, cheetahs, and elephants makes sense also because these species used to live in North America once upon a time. But I would suggest that their prey, such as wildebeest and other antelope species, should be moved in bulk, as well. In addition, I would suggest that Europe and Asia, and especially Siberia, be included in the scheme. There, too, the same species once roamed. My concern is not only for the endangered animals, though. Although humans may adjust to the changing climatic conditions somewhat better than other animals, they are still likely to suffer tremendous losses. In the process, they are likely to revert to some of their old habits. And African animals may well become essential when humans eventually return to hunting and gathering.