School authorities in the American heartland state of Kansas have delivered a rebuff to subscribers to the notion of intelligent design by voting to banish language challenging evolution from new science guidelines.

In a 6-4 vote on Tuesday night, the Kansas state board of education deleted language from teaching guidelines that challenged the validity of evolutionary theory, and approved new phrasing in line with mainstream science.

It was seen as a victory for a coalition of moderate Republicans and Democrats, science educators and parents who had fought for two years to overturn the earlier guidelines.

The decision is the latest in a string of defeats for proponents of creationism, and its modern variant, intelligent design. It reverses the decision taken by the same authorities two years ago to include language undermining Darwinism - on the insistence of conservative parents and activists in the intelligent design movement.

In redrafting guidelines for science teaching, the board removed language suggesting that key concepts such as a common origin for all life on Earth and for species change were seen as controversial by the scientific community.

The board also rewrote the definition of science, limiting it to the search for rational explanations of what occurs in the universe. The move, though limited in its scope, was seen as significant because it rejected a key argument of subscribers to intelligent design: that providing children with arguments for and against evolution merely amounts to fair play.

But Kansas remains a conservative state and many people harbour misgivings about teaching evolution to school children. The school board received a petition with nearly 4,000 signatures opposing Tuesday's decisions.

Overcoming such misgivings will be difficult, said Jack Krebs, a former maths teacher who is president of Kansas Citizens for Science.

"The bigger issue is the cultural divide. The intelligent design people and the anti-evolution people truly believe that science as it is practised is atheistic, and excludes God, and this is really the heart of the cultural battle," Mr Krebs said.

Despite this latest setback proponents of intelligent design remain active across the US. In the last five years, anti-evolution legislation has been introduced in 24 state legislatures and similar policies were under consideration in at least 20 states, according to the National Centre for Science Education in California.

Given the deep passions surrounding the teaching of evolution in Kansas, it is widely expected that proponents of intelligent design will not let up in their campaign over science teaching.

"They have really been on a rollercoaster for the last 10 years in Kansas," said Glenn Branch, deputy director of the National Centre for Science Education. "This isn't really good for the state of science education in Kansas for the treatment of evolution to be in such flux. It probably does have the effect of encouraging creationism in the local classroom."

Backstory

Teaching creationism in American public schools has been outlawed since 1987 when the supreme court ruled that the inclusion of religious material in science classes was unconstitutional. In recent years, however, opponents of the theory of evolution - first developed by Charles Darwin, above - have regrouped, challenging science education with the doctrine of "intelligent design", which has been carefully stripped of all references to God and religion. Unlike traditional creationism, which claims that God created the earth in six days, proponents of intelligent design say the workings of this planet are too complex to be ascribed to evolution. There must have been a designer working to a plan - that is, a creator.