When I was here fifty years ago, I speculated that elephant birds had disappeared because their habitat had dried out, and I put that down to a changing climate.

Now, we know that although the climate here has indeed become much drier, that change took place many thousands of years ago, and that elephant birds living in the spiny forest managed to survive it.

So climate change alone can't be blamed for the birds' extinction.

Are there any other clues that might suggest an alternative explanation for that, and for the fact that the giant lemurs' forests have also gone?

Well, it's been discovered that those giant lemurs all disappeared over a very short space of time, and that was when human beings arrived.

Madagascar was one of the last places on Earth to be reached by human beings.

They didn't get here till around two thousand years ago, and then, of course, there were just a few hundred.

Fifty years ago, there were around six million.

Today, there are twenty million.

Was it human beings who exterminated much of the island's animals, the elephant bird, as well as the giant lemurs?