Legs of Snakes and Religion of Biologists

Legs of Snakes and Religion of Biologists

We wrote about bladderwort genome paper earlier.

Carnivorous Bladderwort Plant Genome Shows Some Designers are More Intelligent than Others

The authors discovered that the genome of the carnivorous plant was packed with protein-coding genes and it thoroughly purged out all ‘junk DNA’. It was the clearest evidence of lack of functionality of junk DNA, because if 80% junk DNA were functional as claimed by ENCODE, 22 Gb pine genome would have coded for lot more function than 82Mb bladderwort. Yet, externally we do not see pine trees doing anything more than bladderwort. They are both multi- cellular, both grow leaves, roots and shoots and both perform photosynthesis. Sure, pine trees are much bigger than bladderworts, but no correlation between physical size and genome size has been shown in plants.

Dr. Jonathan Eisen did not agree and came up with the most logically distorted argument in support of junk DNA.

Most plants have junk DNA, one doesnt. Thus, junk DNA is useless.

Most reptiles have legs, snakes dont. Thus, legs are useless.

The analogy is flawed, as pointed out by T. Ryan Gregory -

Genome Reduction in Bladderworts vs. Leg Loss in Snakes

No, that isnt the logic, and the legless snakes or eyeless cave fishes analogy is flawed. Why?

1. We know that legs and eyes are functional, and we know what they are functional for (walking and seeing, respectively). By contrast, we do not have strong evidence that non-coding DNA is functional or what it may be functional for. Worse, the very existence of so much non-coding DNA itself is taken as evidence that it must be doing something. Therefore, the observation of a plant that lacks a substantial amount of non-coding DNA but gets by just fine suggests that this kind of DNA isnt strictly necessary in order to make a complex plant.

2. If most of the non-coding DNA in a larger genome does serve an important regulatory function, then it means this plant with a tiny genome must have evolved a totally different system for regulating its genes. This strikes me as a rather large assumption and in any case, its one for which we have no evidence. As such, I would argue that it is at least as parsimonious to take this small genome as evidence that non-coding DNA in general does not serve a key regulatory function for the most part.

3. When snakes lost their legs or cave fishes lost their eyes, they also lost the specific ability that legs or eyes provided. Legless snakes cant walk, because the function of legs is walking. Eyeless fishes cant see, because the function of eyes is seeing. The proposed function for non-coding DNA is gene regulation. Unlike the snake or fish example, the bladderwort has lost most of its non-coding DNA but it can still regulate all of its genes just fine.

What T. Ryan Gregory wrote in so much text was summarized by Dan Graur in three sentences.

Thus, a better analogy would be

**Most plants have junk DNA, one doesn’t. Thus, junk DNA is useless.

Most people have imaginary friends (religion), some don’t. Thus, imaginary friends are useless.**

An (unnecessary) imaginary friend

We presume Dr. Graur did not want to mean NIH-funded biologists as those without religion, because, for some, religious practices and leaders evolved with time -

Written by M. //