Science used to trace how creationist anti-evolution tactics have evolved

Scientists use the DNA and physical traits of different living (and extinct) things to figure out where they intersect, spinning the web that connects everything on the planet back to our single-celled ancestors. For his latest study, Dr Matzke swapped genomes and morphological traits with text from legislative proposals designed to keep evolution out of schools and let creationism in.

The efforts to push creationism as a valid alternative to evolutionary biology can be traced back almost a century, when teaching evolution was banned, but Dr Matzke analysed only the 65 bills proposed in the past decade.

Many of these are basically copied from one state to another, making it easy to analyse the slow shifts in language and tactics. "They are not terribly intelligently designed," he said.

Dr Matzke already knew that the anti-science lobby had shifted from trying to keep evolution out of schools (which was deemed unconstitutional in 1968) to trying to give creationism an equal chance in the classroom instead. Around 2006, just after this, too, was deemed unconstitutional, the tactics evolved again. Now, the teaching of evolution is increasingly swept into a larger anti-science fight, one that includes an argument against climate change. "The strategy of encouraging 'critical analysis' of not just evolution and origin-of-life studies, but also of human cloning and global warming was essentially invented in a 2006 school board policy passed in Ouachita Parish, Louisiana, Dr Matzke said in a statement. "This combination proved popular, and legislative bills using this tactic have since been proposed in many states, and were passed in Louisiana and Tennessee."

These bills "encourage critical analysis" of several topics in science, opening the floodgates for science teachers to share pseudo-scientific views. While the National Science Teachers Association strongly supports the teaching of evolution (and only evolution), the organisation warns that teachers in some parts of the country may be pressured to present opposing, pseudo-scientific views, as well.

As recently as 2011, a study found that more than 70 per cent of high school biology teachers avoided taking a hard stance on evolution in the classroom, mostly to avoid potential conflicts. And 13 per cent of those teachers pushed creationism as a possible truth. Although 98 per cent of scientists connected to the American Association for the Advancement of Science say they believe that humans evolved over time, only 66 per cent of Americans surveyed by Pew believe that science has reached a consensus on the issue.

Nearly a third of Americans reject evolution entirely, and around half of those who accept it as good science still believe that a higher power played a part in the process.