There's an Invisible Line That Animals Don't Cross. Here's Why.

The animal kingdoms of Asia and Australia are worlds apart, thanks to an invisible line that runs right between the two neighboring continents.

Most wildlife never cross this imaginary boundary, not even birds .

And so it has been for tens of millions of years, shaping animal evolution in different ways on each side.

It all started about 30 million years ago , when the Australian tectonic plate bashed up against the Eurasian tectonic plate and created an archipelago, rerouting ocean currents and creating new regional climates.

On one side of the map, in Indonesia and Malaysia, monkeys, apes, elephants, tigers, and rhinos evolved; while on the other side, in New Guinea and Australia, marsupials, monotremes, rodents, and cockatoos flourish. Very few species are abundant on both