Conversely, why, according to Guns, Germs, and Steel, DID Australia's aborigines lose out to invading Europeans?

The answer
to this can be found in Chapter 15.

First, we must think about why this
question uses the word conversely.  This word seems to be contrasting the Australian
aborigines with some other group.  To answer the question, we must know which group this is.  As
it happens, the group is the natives of New Guinea.  These...