South East Asia comprises a small but distinct part of the Asian continent, plus a seemingly endless array of large and small islands, that are biologically amongst the richest and most complex on earth. It is home to iconic species like orang-utans (the only great apes outside Africa), elephants, tigers and rhinos that owe their origins to the Asian continent but also supports species that have affinities with the Australasian region. This is a consequence of the region lying at the convergence of two great tectonic plates that have effectively brought species into intimate juxtaposition that originated far apart: a phenomenon that was first explained by Alfred Russell Wallace.