In 1857, Broca was presented with a hybrid leporid, a result of a cross species reproduction between a rabbit and hare. The crossbreeding was done for commercial rather than scientific reasons, as the resulting hybrids became very popular pets. Specific circumstances had to be set up in order for differently behaving species to reproduce and for their hybrid descendants to be able to reproduce between themselves. To Broca, the fact that different animals are able to intermix and create fertile offspring did not prove that they were of the same species.