In my last post on a ‘creationist biology curriculum’ I asked the question: what, exactly, do they teach? Over on the Sciblogs site (where this blog is syndicated), a commenter answered by pointing me at another school’s curriculum. As I read through it, I could feel the area beneath my collar getting distinctly heated.
This was partly due to the sections listing Commonly accepted science we believe in and Commonly accepted "science" we do not believe in. What we have here is an a priori assumption about the world, followed by rejection of anything that doesn’t match that particular worldview. This is not how good science is done. (And note the use of scare-quotes denoting the science that the authors don’t believe in.) And this makes me wonder just how well their students will understand the overarching strand of the national science curriculum, the nature of science.
It also reflects a fundamental misunderstanding, misinterpretation, &/or misrepresentation of the science. For example, under the list of stuff they choose not to belief, we find this (emphasis in the original):
Neither do we believe that genetic information can increase, or ever has increased, in complexity over time. New genetic information (eg: a random mutation) must be useful to the carrier to eventually be prevalent in the population (natural selection is on the creationist side), and it must add genetic information to support evolution theory. Such mutations are unknown to science. The very small number of known useful mutations, and the best examples in textbooks, all switch off or damage a pre-existing metabolic pathway. They do not add additional, useful information. Also, if the environmental condition which caused the mutation to be useful (eg malaria for sickle-cell anaemia, antibiotics for bacteria) is removed then the mutation is discovered to be harmful and the "useful" mutation is selected against by natural selection.
Now this is just plain wrong! And at best it indicates a lack of knowledge about modern genetics. A mutation that results in the duplication of a gene, for example (the ‘jumping genes’, or transposons, are often involved here) will result (& has resulted) in an increase in ‘genetic information’. The family of human haemoglobin genes is one such example, and if you want historical evidence of duplications then you need go no further than pseudogenes, which litter the mammalian genome and provide very good indicators of phylogenetic relatedness and – dare I say it – evolutionary change. (This paper on the evolution of the haemoglobin genes is behind a paywall, but there’s a good general article on Wikipedia.)
Another example of a well-known gene-duplication mutation is the differences in salivary amylase gene copy-numbers between different human populations. Yes, of course some increases in copy-number can have harmful results – the point here is that contrary to the assertions in the curriculum I’m looking at here, some mutations can and do result in an increase in genetic ‘information’ (copies of genes) that is beneficial to the individuals carrying those mutations. Such mutations are not ‘unknown to science’!
The statement that a mutation must add genetic information to support evolution theory is simply a straw man: all that evolution requires is a change in information that results in a change in phenotype that may be subject to natural selection…
As for the final sentence in that quote, well, the best that can be said is that the author really doesn’t understand the thing they are criticising (or the things they accept, seeing as how they say that natural selection is acceptable). Context is important! Conditions in a given environment may select for particular mutations (in mitochondrial DNA, for example), but the same mutation may well be selected against in another environment. No surprises there, it’s what evolutionary biology predicts. Being heterozygous for the sickle-cell allele conveys a selective advantage in regions where malaria is common – an advantage over both homozygous ‘normal’ individuals (who tend to die of malaria) and people homozygous for sickle-cell (who die from the multiple phenotypic effects of this disease). In a different context ie in the absence of malaria, then the ‘normal’ phenotype will win out. Guys, this is how natural selection operates!