According to Guns, Germs, and Steel, which continent had a head start in 11,000 BCE?

In Chapter 1, Diamond is essentially saying that no
continent truly had a head start in 11,000 BCE.  11,000 BCE is just before the time when
agriculture is discovered.  Before this, no continent had any real sort of an advantage
in Diamond's mind.

Diamond says that all the continents
could have been said to have advantages at this time before agriculture began.  He says,
for example, that you could predict that Africa was the best off because it had been
populated by human beings for longer than any other continent had.  However, he says,
you could make just about as good a case for any of the other inhabited
continents.

The point of this is that all the continents
were essentially equal in 11,000 BCE.  It was only the development of agriculture that
caused them to diverge in the years following that date.