Mice might be small, furry and have a tail, but biologically they are very similar to humans - genetically, there is only 2.5 per cent difference between us compared with 1.5 per cent difference with monkeys. These similarities have allowed mice - and other animals - to play a critical role in medical research for more than 100 years, helping us develop life-saving drugs and vaccines. It is estimated that between 50 and 100 million vertebrates are used for medical tests each year worldwide. The numbers for insects and worms - or non-vertebrates - are thought to be higher but not recorded. According to the British Royal Society, we have all benefited immensely from scientific research involving animals. 'From antibiotics and insulin to blood transfusions and treatments for cancer or HIV, virtually every medical achievement in the past century has depended directly or indirectly on research on animals,' said a society spokesman. But it remains a highly controversial issue. Animal rights groups, such as the Animal Liberation Group and Speak, argue that testing is immoral: the benefits to humans do not outweigh the pain suffered by the animals. Members of such groups believe that every animal has a right to life just as humans do, and that it is wrong to test experimental drugs on animals, often leading to their deaths. But, even if many people sympathise with such a view, the terrorist tactics used by extremist animal rights' groups have led to dwindling public support. In February, for example, Mel Broughton, a British animal rights campaigner, fire bombed some of Oxford University's research facilities. Broughton, who is a leading member of Speak, said that a planned GBP20 million (HK$256 million) expansion of the university's animal research facilities was unnecessary. He was jailed for 10 years. A spokesman for Oxford University said that it accepted the rights of protesters to voice their objections, but would not tolerate the breaking of laws and terrorising of its staff. Edythe London, a professor at the University of California, Los Angeles, had her home flooded by activists after they discovered she was testing drugs on animals. Meanwhile, a 2009 Gallup poll in the United States showed that 57 per cent of Americans were in favour of medical testing on animals, even though they largely opposed testing cosmetics such as eye shadow. Most cosmetic manufacturers say their products are no longer tested on animals and the European Union has initiated an EU-wide ban from this year. But the world's largest cosmetic manufacturer, L'Oreal, has protested against the ruling and France is challenging it in the European courts.