They are the only primates to have short 'flush' canine teeth.

The only primates in its woods and fields are human beings.

Aye-ayes are the only primates known to have this strange adaptation.

They are the only primates known to do so.

But humans aren't the only primates that can pack on the pounds when their mates are pregnant.

Besides humans, they are the only free-living primates in Europe.

What is the only wild European primate, and where does it live?

The aye-aye is thought to be the only primate which uses echolocation to find its prey.

Koko wasn't the first, and isn't the only primate to have learnt to communicate with humans.

But why did humans, the only hairless primates, lose their body hair?