Gazing out of my window pondering how to start my review of Ana Mendieta, I noticed a creeper engulfing the house at the end of my garden. Having covered the wall, one window and a chimney, the tentacles are spreading along the gutter and over the roof. Meanwhile, my neighbour’s roses have encroached six feet into my territory and, next door the other way, a vine is assiduously working its way along the hedge and into the branches of a tree. Nature, it seems, is quietly overwhelming north London.

The Alternative Guide to the Universe, an exhibition of work mainly by self-taught practitioners, encourages one to speculate on the merits of orthodox art and science compared with the wild schemes pursued by these eccentrics and visionaries, some of whom are inspirational while others bludgeon you with their offbeat ideas. 

Central to this thoughtful show is not really the use of light in art per se but how light appropriately serves a post-minimalist shift from the work of art to the environment itself. For the most part, the works here endeavour to shape the space around us or invoke a response on a physiological level.

On the 35th anniversary of the year punk met the mainstream, it’s to be expected that retrospection and nostalgia are in the air. Television has had a go, albums are being reissued and old soldiers are telling their stories. By its very nature an anniversary suggests that things were cut and dried, that 1977 was a beginning or a marker in the sand.

At the Hayward Gallery a young woman falls over backwards; her flight is magically arrested at a gravity-defying point of imbalance. Since she is blinking, one can safely assume that she is alive, present, and human rather than a waxwork or an illusion. How, though, does she sustain such an impossible position? No wires are visible, so she can’t be suspended, but look carefully and you can detect a rigid frame of some sort, hidden beneath her clothing to prevent her from crashing to the ground.

In May 1958, Yves Klein invited the Parisian art world to the Galerie Iris Clert for the opening of his latest exhibition, which was entitled The Specialisation of the Sensibility in the Raw Material State of Stabilised Pictorial Sensibility. Driven by ample press coverage, large crowds eagerly awaited the unveiling of the artist’s latest creation, only to be met with nothing. The gallery was empty and the artist best known for his eponymous shade of blue had left colour far behind and painted the entire space white.

It has been nearly a century since modernism decreed that “art” is whatever is produced by an artist, and “an artist” is whoever claims to be one. Mostly I agree with this, and my eyeballs tend to roll back in my head when the conversation moves on to the “my three-year-old could do this” refrain. But I’ve got to say, with David Shrigley, a lot of me spent a lot of time in the Hayward thinking, “Um, is this art?”

The easiest mistake to make in appreciating George Condo would be to assume that his manic style reflects a manic creation or a manic practice. Some of Condo's paintings and drawings, with their childlike loops and gurning, disfigured faces, look like he made them in a fit of violence or some hysterical trance, but the real surprise of two new shows at the Hayward Gallery and at Sprüth Magers in Mayfair is the care and the calmness that lies behind them.

In 1997 the Swiss artist Pipilotti Rist produced one of the most delightful videos ever made, and it won her the Biennale. Ever is Over All shows a young woman skipping down a city street gaily smashing car windows with a red-hot poker; and since it is shaped like a knobkerry, the flower makes a surprisingly convincing weapon. Oh dear, though, here comes a policewoman; but instead of admonishing or arresting the vandal, the bobby gives her an encouraging smile, salutes and walks on by. 

That Tracey Emin is one of the defining personalities of our time isn’t in doubt. Even if you never want to hear another second of her guileless wittering, another word about her abortions, traumatic early rape and relentless onanistic neediness, you can't deny that her self-effected transformation from chippy Margate outsider to big-league art-world player represents something extraordinary.