Spain's parliament is to declare support for rights to life and freedom for great apes on Wednesday, apparently the first time any national legislature will have recognized such rights for non-humans.
Parliament is to ask the government to adhere to the Great Ape Project, which would mean recognizing that our closest genetic relatives should be part of a "community of equals" with humans, supporters of the resolution said.
The move in a country better known for bull-fighting would follow a string of social reforms which have converted Spain from one of Europe's most conservative nations into a liberal trailblazer.
Backers of the resolution expect support from the Socialist Party of Prime Minister Jose Luis Rodriguez Zapatero, whose government has legalized gay marriage and reduced the influence of the Catholic Church in education.
"With this, Spain will make itself a world leader in protection of the great apes," said Pedro Pozas, general secretary of the Great Ape Project's Spanish branch.
The resolution, presented by a Green Party parliamentarian, prompted criticism and some ridicule at first.
Spanish media quoted the Catholic Archbishop of Pamplona as saying it was ludicrous to grant apes rights not enjoyed by unborn children, in a reference to Spanish abortion laws.
But a spokesman for Archbishop Fernando Sebastian said he had been taken out of context and now supported the resolution.