This week saw the discovery of Marree Man, an immense patently inauthentic 4 kilometre ground carving in the desert in northern South Australia. Aboriginal people will once again need their sense of humour. The mere fact that there is enough apparently flat, apparently empty ground out there in the outback to draw on with a tractor as if the land were a piece of paper is really amazing. It is like an illustration of terra nullius, the ultimate tabula rasa at the same time as it proclaims: this is Aboriginal land, so pay the rent.

Of course the tastelessness of the work could have originated in black or white Australia, (though purportedly it was made by non-Aboriginal tour operators looking for a special attraction for Marree). Like the circulation of the Nullarbor Nymph across a credulous globe, Marree Man shows that the world is ready to believe there be marvels in Australia, outlandish antipodean marvels. You have to laugh.

Black Humour, a show curated by Neville John O'Neill in Canberra (always good for a smirk) for the Canberra Contemporary Art Space celebrates the sense of humour of black people in Australia and it shows them in many cases having to find something to laugh at in order to keep from crying. Political and angry, many of the works are more barbed than beautiful, their agenda is to attack, to register affronts and re-view history.

Bianca Beetson's work adopts a strong spirit of fun; you look at her two images of toilets in multiple shades of pink plus pink glitter, and think what is this? Then you notice in one of them the toilet seat is up, in the other it is down, men's story, women's story. Beetson's other works combine pinkness with toxicity. Deadly.

The research that Brenda Palma has done into the use of Aboriginal figures in advertising has provided her with a wealth of material that is bittersweet in its humour. The Abo brand sanitary white paint is particularly funny and mystifying, a bit like striped paint. Or how about white Australia pineapples and Golden Fleece soap will keep Australia white?

The witch of Ipswich, Pauline Hanson, features quite a bit in the exhibition though it was planned before she became visible. The Campfire Group made a fish and chip shop display counter, filled it with crudely made Aboriginal-art-looking wooden fish, chips and calamari rings and then went to town thinking of satirical distortions of fish shop paraphernalia and language. Lots of puns and I got a few laughs from the canned ideologies best before 1788, the tart-arse sauce, Pauline's white vinegar which " must be taken with a grain of salt, add liberally and blame others - will sour relationships" and the cooking instructions for use: "Please explain." The Group also made postcards featuring the fish and chip shop which are total collectors' items.

Laurie Nilsen of Campfire also shows a set of fish representing "different pecking orders in Australian society". The four fish are on steel rods coming out of a solid platform which stands in for "Aboriginal culture...the basis and foundation for the development of Australian culture and society".

The three paintings by Harry Wedge in his trademark thick dot ugly wildman style are more poignant than funny . One of them has the words Pauline Hanson Amoral sliding down it as if in melted rage or is it cheese? Then there is Chip on shoulder Brook Andrews' charming image of a friend eating fish and chips from a Hanson news-storied paper.

One of the most complicated works is Julie Gough's The subdividing games: pogography 2000 - tool for land reclamation vs tools for land degradation which uses juxtapositions of objects to make a point about land claims. She has made cushions for each state and territory out of an Australian flag and marked them with muddy large dots.
These pogostick marks, not dot paintings but still dots, represent an indigenous engagement with the land and are counterposed with fencehole diggers and other tools used to make holes in and abrade the land. The pogostick makes a dot as a substitute for the sign Aboriginal identity. Though the success of Aboriginal dot paintings has changed the profile and status of all Aboriginal people it can be a problematic sign because it locates 'true' Aboriginality in traditional societies and thus does not account for the diverse identities of rural and urban groups. Sue Elliott also uses the dot, in this case thick dots on old bits of cardboard, as a sign for the consumption of Aboriginal culture that ignores the conditions of its production.

I know there is such a thing as an Aboriginal sense of humour, I've seen Destiny Deacon in action, it's very Australian, dry, self-deprecating, inventive. I know there is such a thing but why?