In Texas, a battle is brewing over the teaching of evolutionary theory, as the Board of Education considers a new set of instructional materials to be used in science classrooms.

In several states there are laws or standards that allow educational authorities to add material that isn't in the textbooks to the curriculum; usually these are designed to supplement the text, for example if it is out of date, or add activities or problem sets that students might do.

The submissions have to meet certain standards. In 2009 the Texas Board of Education said that students should be taught all sides of current scientific theories.

One submission has come from a company called International Databases, LLC. It's a one-man operation run by Stephen Sample, who says he has a degree in evolutionary biology and taught at the high school and junior college levels for 15 years.

The material he submitted consists of eight modules dealing with current issues in biology and ecology. Most are well within the mainstream scientific consensus. But there are two that deal with the origin of life. Those sections say the null hypothesis is that there had to be some intelligent agency behind the appearance of living things. It is up to the scientists proposing a naturalistic explanation to prove their case.

A null hypothesis is used as a way of describing a default position in science. For example, a null hypothesis might be that there is no relationship between smoking and cancer. That hypothesis is falsified when lots of people smoke and get lung cancer, absent other possible causes.

That wording drew the ire of the Texas Freedom Network and the National Center for Science Education, which described it as stealth creationism because they posit that the default hypothesis for life's origin has to be that there was an intelligent agency involved.

Ordinarily teaching from a religious perspective is forbidden in public school science classes. The principle was decided on in the Kitzmiller v. Dover case, in 2005, when a judge ruled that teaching the theory of intelligent design was actually a form of religious instruction and therefore not allowed in public schools.

Sample says the null hypothesis is such because the old experiments that attempted to produce building blocks of amino acids failed to do so. In addition later experiments that produced other precursor chemicals, such as DNA and RNA, required very specific conditions in a lab, and aren't, he said, necessarily reflective of what the early Earth was like. Therefore, the odds of making life from non-life seem too small for a naturalistic hypothesis to work.

Sample says it isn't stealth creationism -- he says the intelligent agency might just as well be aliens. But he emphasizes that he wants students to learn to think critically, and that unlike the physical sciences, there aren't any experiments you can do to demonstrate evolutionary theory.

Nick Matzke, is currently a doctoral candidate in evolutionary biology at the University of California, Berkeley, and the former public information project director at the National Center for Science Education, disagrees. He notes that there has been a lot of work in recent years on molecules that catalyze their own formation, and increase their concentrations in solutions. The molecules don't replicate themselves in quite the same way that DNA does. But they do offer insight into how life might have started. The thing is, scientists are limited by a single lab experiment, he said. When you have a million experiments like that going on all over, in every tide pool, then you can get many results.

Josh Rosenau, programs and policy director at the NCSE says part of the problem is the way the bills that allow such materials are worded. They almost always talk about critical thinking, which nobody would be against. But the laws allow teachers to bring in materials that can reflect religious biases without being disciplined by a school district.

Evolution is still controversial enough that some teachers back away from teaching it entirely, as a study from Penn State University in January found.

The problem with evolution, says Robert Luhn, director of Communications at the NCSE, is that it touches on something close to people. You don't get this kind of thing when talking about gravity, he said.