Take that look off your face ...

Natural History Museum, London
Hatred and love
Hatred and love from Darwin's book The Expression of the Emotions in Man and Animals. The images form part of Mark Haddon's piece 24 Emotions. Photograph: Natural History Museum

Charles Darwin had little time for art. He laments this fact in his memoirs. Not only had he lost all taste for pictures by the age of 30, he found them useless as any kind of evidence. During three entire decades of research for his last great work, The Expression of the Emotions in Man and Animals, Darwin scoured the old masters relentlessly. There were, he concluded, no decent images of extreme emotion anywhere to be found because painters were much more interested in beauty.

For illustrations, he used photographs, etchings and the plates from Duchenne's famous Album of Pathological Photographs in which the pioneering French neurologist used electric shocks to demonstrate the mechanics of facial expression. Duchenne showed that smiles, for instance, find their expression in both the mouth and the eyes, that the lips retract when a person is in agony. He investigated 13 expressions but Darwin went all the way to 24, and there might have been others had he seen more of the works of Rembrandt, say, or Caravaggio.

But Darwin's concerns, and the questions he raises in that book - are smiles unique to humans, why do cats purr, why does laughter take the form of rapidly reiterated sounds in both monkeys and men - are all about demonstrating an evolutionary continuity between people and animals. And not just a continuity in the range of expressions, from baring one's teeth to frowning in recoil, but in the original emotions themselves. Darwin argues that feelings, like the beaks of finches and the eyes on the peacock's tail, are the creation of evolution itself.

This book, as controversial now as it was then, provides the occasion for another of this year's Darwin anniversary exhibitions, this time at the Natural History Museum. Any number of art works could have been included - think of Fuseli or Géricault, just as obsessed by facial expression as Darwin - but the decision to keep it contemporary is a good one, and not just because there is so much white-coat art around these days.

The American artist Diana Thater, for instance, has made a simple-seeming work of considerable beauty and complexity that consists entirely of a video recording of female gorillas clambering around a park in the Cameroons. All the usual responses - how like us they are, how human their expressions, how close but how far - are upended with one cunning device. The video is projected against the gallery walls with such precise coincidence that the gorillas appear to be navigating the Victorian architecture itself.

Their inquiring faces turn back upon ours: how strange that we should all be in this one world together.

The French photographer Gautier Deblonde has been deep into the museum's zoological storerooms; "a forest of glass eyes/ at the end of the Circle Line" as Ruth Padel's accompanying poem has it. There he notices the way that mankind poses animals according to our own interpretations and interests. Giraffes, at the hands of the taxidermist, become their own symbol - rows of elongated necks. Stags are reduced to antlers. Lions stand rampant upon cardboard rocks, kings of the animal world. Pose equals expression equals emblem: animals become heraldic.

The Turner prize winner Jeremy Deller has produced an installation in conjunction with a magician and a documentary film-maker which centres upon human methods of animal observation, specifically of expression, but with a twist so startling and ingenious it would spoil the effect to reveal it.

And Tina Gonsalves's entire enterprise in the last decade draws a direct line from Duchenne to Darwin to Paul Ekman's famous database of facial expressions, adding the dimension of time. Her subjects appear on screen in a grid of little videos, their emotions seeming to overflow from one chamber to the next in a tide of mutual experience. Gonsalves fixes upon only six emotions and yet the expressions on screen are infinitely variable. What is lost in Darwin is - of course - our individuality.

After Darwin includes an early work by the video artist Bill Viola that has become famous for its exceptional use of documentary footage. I Do Not Know What It Is I Am Like is over an hour long, an enthralling and bewildering stream of images: roving bison, the slow-shuttered gaze of an owl, a dog attacking the camera, a chick hatching from an egg on the artist's table.

And there is Viola himself, reflected in droplets, the chromium plate of the tap, even in the eye of the owl.

Our place in the animal world, their place in ours: through splicing, ambient sound, long and short cuts, a set of visual analogies is developed between their daily behaviour and our own that culminates in a sequence showing fire-eating rituals in Fiji. Are we more rational than apes? Where is the line between instinct and reason?

This work alone is worth the visit but the most moving contribution here is a set of brief and brilliant stories by the novelist Mark Haddon. Faced with Darwin's 24 faces, abstracted from all living context like the dead specimens in the museum itself, Haddon gives each a presence, you could say a raison d'etre, in prose. His story of sorrow is overwhelming - a destroyed object, a destroyed relationship - but its last line perfectly conveys the mysterious disappearance, and reappearance, of emotions like a cormorant in a river, which science can never explain. "You stand there with tears rolling down your cheeks and have no idea why."