Richard Dawkins' Tale Continued

I have to admit: Richard Dawkins really was quite clever the way he visualized evolution's timeline in The Ancestor's Tale.

When I last studied the classification of animals and plants, I remember being shown huge laminated "flowcharts" with animals (now called metazoa or eumetazoa), plants, and protozoa at the top, and then dividing down from kingdom to phylum to class to species, or whatever the progression was. To a high school student it was overwhelming and really didn't make a lot of sense, and certainly wasn't all that exciting, except to someone interested in classifying life on earth. Yes, it was interesting to see the classification but I wasn't smart enough to understand the first derivative: the role of evolution in producing that chart.

I attended a public school and, as far as I remember, there were no issues about teaching evolution at that time, back in the 60s. I went to church on Sunday and was as faithful and as much a believer as any typical North Dakota kid. The operative word is "typical" and it is very inclusive.

Earlier this week, I was teaching high school students about cnidarians and sponges. As mentioned earlier, that was a weak area in my high school biology teaching. Maybe I missed school that day. More likely, living in North Dakota, as far away from an ocean anyone could get, I could not relate to marine creatures.

Last week, all of a sudden, I found cnidarians and sponges exciting. So exciting I have fleeting thoughts of proposing to the school administration to let me teach an elective to college-bound students interested in biology using Richard Dawkins Tale as the text.

Now I get it.  I understand what it means when they say the sponges are the most ancient of animals. I understand why sponges are even considered animals. I know what cnidarians are. I know how they got their name. Most importantly, I understand how classification of life forms brings evolution, the first derivative of classification, to life.

Dawkins has two short chapters between cnidarians and sponges. One chapter is on ctenophores, jelly combs, which have a superficial appearance to jelly fish. The other chapter is on placozoans. This phylum as one species: Trichoplax adhaerens. This is a most unusual life form, and it was probably a challenge trying to figure out if it was even an animal. According to Dawkins, "there is not much in its anatomy to connect Trichoplax with any other kind of animal." Dawkins presciently adds at the end of that chapter: "Understandably, there is now some strong lobbying for Trichoplax to join that select company of organisms whose genome is completely sequenced. I think it will happen, in which case we should soon  know what this strange little creature really is."

The Tale was copyright/published in 2005. I am thrilled to report that Nature published the results of genome sequencing for Trichoplax adhaerens on August 21, 2008. The conclusion: "The compact genome shows conserved gene content, gene structure and synteny in relation to the human and other complex eumetazoan genomes....its genome encodes a rich array of transcription factor and signalling pathway genes that are typically associated with diverse cell types." Elsewhere it was stated that Trichoplax shares over 80 percent of its genes with humans.

Very, very exciting.