Paedomorphism can be a mechanism for differentiation between species. Here the authors demonstrate that bonobos take longer to reach adult levels of two behaviors than do chimpanzees, providing an empirical demonstration of this hypothesis among our closest relatives.
Brosnan, S.F. (2010). Behavioral Development: Timing is everything. Current Biology, 20(3): R98-100. doi: 10.1016/j.cub.2009.12.009