Campaigners who want four great ape species to be given legal rights believe they may be on the verge of victory.

The four species are chimpanzees, bonobos (a pygmy chimp), orangutans and gorillas.

Will Self and Professor David Penny discuss why apes should be given rights

A number of groups have been campaigning under the banner of the Great Ape Project (GAP) for all four to be given what are sometimes called human rights.

GAP says it may soon achieve a breakthrough, if a new animal welfare bill in New Zealand is drafted to include a clause to do just that.

The law would then make the great apes the first non-human species to enjoy individual, fundamental rights.

Enforceable in law, they would include the right to life, the right not to suffer cruel or degrading treatment, and the right not to take part in most experiments.

The bill could soon become law and could set a precedent for other countries.

GAP argues partly from the genetic similarities between the great apes and human beings - chimps and humans share 98.5% of their DNA.

But it also says all four species have some "indicators of humanhood" - intelligence, deep emotions, some linguistic ability, and self-awareness.

Shared path

Dr Jane Goodall, renowned for her work with chimps in Gombe national park in Tanzania, describes GAP as "a good starting point".

Dr Jane Goodall explains why she supports the Great Ape Project

"The genetic similarity means we have a special kinship with the great apes, we share an evolutionary path.

"The crucial thing when we are wanting to give rights to non-human beings is - can those beings feel? Are they sentient and are they sapient?"

Gorillas - close enough to us to count

Dr Goodall says GAP is not about human rights, but about starting to extend to other species "certain basic rights that we extend to the human family".

But GAP has its critics. Some say that, because the apes look like us, we cease to be objective and start seeing similarities where none exist.

Others believe GAP is exaggerating the supposed similarities of the apes to stop their use in experiments. Some of these counter arguments are featured in this week's New Scientist.

Great apes have never been used for research in New Zealand itself and are no longer used in the UK.

But about 1,700 chimps are kept for research in the US.

Only a start

GAP is also criticised for choosing what some see as an arbitrary cut-off point - the differences between apes and other animals.

Why not give rights to monkeys as well, and to elephants, dogs and every other creature down the line, ask critics.

More in common than meets the eye?

Dr Goodall adds: "One has to make a start to break the arrogant perception that most people have that we are totally different."

Many GAP supporters accept that argument, not as a criticism, but as the way forward in what Dr Goodall calls "extending the circle of compassion, first of all to our closest living relatives".