Wednesday, November 11, 2009

Chromosome fusion viability

Regarding my comment that "creationists claim that such chromosomal fusion or fission events are bad and don't happen" in this morning's post, A reader writes,
Who are these "creationists"? Is it a strawman, really big brush, I
don't know, I have it on good authority, or what? ... It would be far preferable to ... give names. Else it looks like everyone else except you, or it becomes a sentence evolutionists can use to attach any creationist.
Fair enough. For the record, when I address creationist ideas in that way, I avoid mentioning names for two reasons:
1. It's a common enough argument, and I'm too lazy to look up specific references.
2. I don't want to name specific names because I'm not looking to pick a fight. People are way too sensitive about this sort of thing.

But my reader has a legitimate point. If this was a formal publication (and not just my own personal soapbox), I would be expected to give citations and never, ever refer to "some people." The following paragraphs detail some examples of what I was trying to describe.

Walter Lammerts, past president of the Creation Research Society:
... species show remarkable variation in chromosome number and form. Translocations and inversions occur rarely and spontaneously in species populations. ... none of them are more vigorous than the normal or standard type.

John Klotz in a 1969 issue of CRSQ:
Only polyploidy and chromosomal rearrangement show any promise as a mechanism for evolution, and in the final analysis these contribute nothing that is really new. Moreover both usually result in a substantial reduction in viability and fertility.

Here's Will Brooks in the most recent issue of Reason & Revelation:
Chromosomal rearrangements of this nature are not easily passed to offspring. When mutations of this magnitude occur, they pose serious problems for an organism when the process of gamete production occurs.

Though I'm sure he'd deny being a creationist, Casey Luskin gets quoted by creationists often enough (compare Luskin's argument with Brooks's above):
In most of our experience, individuals with the randomly-fused chromosome can be normal, but it is very likely that their offspring will ultimately have a genetic disease. A classic example of such is a cause of Down syndrome.

To be fair, other creationists do not have a problem with chromosomal fusion. Jean Lightner, for example:
The possibility of human chromosome 2 being the result of a fusion is not a problem for creationists.
Jim Gibson doesn't mention any viability criticisms of chromosomal fusions in his paper on chromosome evolution.

Looking over this, I guess I should have been more specific about what I meant. I could have written something like this, "Some creationists give the impression that chromosomal fusions or fissions are almost always detrimental and therefore unlikely to become common in a population." Then if I was feeling really generous and ambitious, I could have cited some of the works above. But I didn't. Consider this my penance.

Brooks. 2009. Of apes and men: chromosome 2 in humans and the chimpanzee. Reason & Revelation 29(11):81-84.

Gibson. 1986. A creationist view of chromosome banding and evolution. Origins (GRI) 13(1):9-35.

Klotz. 1969. Chromosomal changes - mechanism for evolution? CRSQ 6(1):45-48, 54.

Lammerts. 1969. Does the science of genetic and molecular biology really give evidence for evolution? CRSQ 6(1):5-12, 26.

Lightner. 2007. A tale of two chromosomes. Answers in Depth Accessed November 11, 2009.

Luskin. 2005. And the Miller told his tale: Ken Miller's cold (chromosomal) fusion. Evolution News and Views Accessed November 11, 2009.