Unlike the prey-bots, which can gather energy from high-powered lamps by their solar panels, the predators can only replenish their batteries by sucking the life out of their victims. The artificial vampires do this by plunging sinister metal fangs into the heart of the smaller but more nimble prey and stealing their electricity. What makes this experiment more than just a jazzed-up version of Robot Wars is that Sharkey's machines are genuinely autonomous.

They take their own decisions in real time. Human intervention is reduced still further by allowing the robots' brains to evolve by means of natural selection. Every so often, the virtual genes that encode the best robot control systems are used to create a new generation of predators and prey. The hope is that this process of artificial evolution will lead to the emergence of complex pack behaviour, similar to that which natural evolution has produced in species such as wolves and lions.

The idea of allowing robots to evolve has given rise to a new but rapidly expanding field of research known as evolutionary robotics. Although it shares many of the insights of artificial life, which pioneered the use of genetic algorithms in the 1970s and 1980s, evolutionary robotics is distinguished by its insistence on making the leap from 2D computer-animations to 3D physically embodied machines.

The aim is to remove the human being from the process of robot construction, so that robots can eventually reproduce and maintain themselves without help. In other words, the aim is to create a whole new species from scratch - a species of organism unlike any that has appeared on this planet, composed not of cells and DNA, but of metal and plastic. In the words of Steve Grand, whose groundbreaking computer game Creatures was among the first pieces of entertainment software to incorporate the principles of artificial life, the leading scientists in this field aspire to be nothing less than latter-day Baron Frankensteins.

But what is the point of such an endeavour? Researchers argue that autonomous robots could prove useful in a range of fields, from clearing landmines to space exploration. But concerns have also been raised about the potential dangers. Kevin Warwick, professor of cybernetics at the University of Reading, foresees a time when intelligent robots may pose a threat to the survival of humanity. For the time being, however, such warnings seem premature; the robots professor Warwick put on display during his Royal Institution Christmas lectures in 2000 inspired more laughter than fear, thanks to their reassuring tendency to break down.

Yet it is doubtful that evolutionary robotics will attain its objectives while it concentrates on the aggressive behaviours that have dominated both the research and the public imagination.

As long as scientists focus exclusively on the evolution of robot predators, and TV coverage of robotics merely panders to our appetite for new forms of violence, robots will never get very far. Violent robots may evolve primitive emotions such as anger and fear, but if the history of life on earth is anything to go by, that will only take them to a level of complexity approaching that of insects. To evolve the greater levels of complexity we observe in higher animals such as ourselves, robots will have to acquire a broader repertoire of emotional capacities. It will not be enough for them to get scared and angry; they will need to be able to feel surprise, to experience joy - and even fall in love.

Before you dismiss such talk as far-fetched, consider the following experiment in preparation at the University of Bath. A population of robots will be divided into two sexes. Each robot will try to reproduce by mating with others, but unlike the experiments conducted up to now, these robots will be fussy about who they mate with. The hope is that, by introducing mate choice into the process, artificial evolution will be accelerated, just as occurs with natural evolution. The technical name for this phenomenon is sexual selection, and its fruits are among the most eye-catching in the natural world - the peacock's tail, the bower bird's nest, the baboon's bottom.