In my previous post about Paul Nelson’s weirdly ignorant view of nematode evolution, Kevin Anthoney made a prescient comment:
Remember that Nelson’s got this bizarre linear view of evolution which starts with a single cell creature, which evolves into a creature with a few cells, which evolves into one with a few more cells, and so on until you reach the 1031 cells in the nematode today. It wouldn’t surprise me at all if Nelson thought that the creature at the 150 cell stage in this process had to be like a modern nematode at the 150 cell stage of development.
The Discovery Institute has responded. I got as far as the massive projection in the following paragraph before giving up.
He acknowledges that the unit of selection (the stage of an organism’s life cycle that natural selection selects) is the individual capable of reproduction — in other words, the adult. And I infer from this that he believes there must have been a step-wise selectable pathway from a single cell to multicellular adult, each step of which was both viable and capable of reproduction. [Their emphasis –pzm]
No, I don’t think that. It seems Anthoney was right: these people have this imaginary model of development and evolution in their heads, in which the 150-cell stage had to have been viable and free-living, and capable of reproduction, in order for it’s specific pattern of differentiation to have been selected. I’m arguing the exact opposite.
A functional end result was selected for, just like in a game of poker, where a winning hand is ‘selected’ — however it got to that point. A full house is a full house whether it was dealt straight to you, whether you drew one card or two. As I mentioned in the previous post, there are multiple ways for development to produce a working worm, and I cited a paper that discussed the taxonomic variation present in various nematode species and genera.
Just to add another detail that kills their design model: that pedigree of cell divisions that produces the adult worm yields 1,090 cells…but 131 of them die during development, leaving no descendants, to produce a canonical nematode with 959 cells. That’s a wastage of 12%! Shouldn’t it be obvious that this animal was not optimized at each stage of development?
Expect to see more from the Discovery Institute on nematodes in the future. It doesn’t matter how often they are refuted, or that all of the investigators of worm development use evolution as a framework to understand what’s going on — they’ll just hammer that dead worm into the ground.
Which should come as a surprise to absolutely no one. Creationists have always argued against misrepresentations or strawman versions of evolution, and rarely against the actual thing. You see it in Behe’s assumption that evolution must build sequentially and toward ever increasing complexity and fitness, with no regard to or recognition of neutral mutations, or of negative ones that propagate due to lack of selective pressure, or of multiple parts/functions evolving simultaneously, or of adaptations or functions being lost/changed along the way. You see it more simply (and stupidly) in the “why are there still monkeys” type arguments. That Nelson also is railing against a version of evolution that no evolutionary biologist actually uses is completely par for the course.
I recently noticed this preprint from the Lenski lab, Viruses playing poker!
Selection for Intermediate Genotypes Enables a Key Innovation in Phage Lambda,
Alita Burmeister , Richard Lenski , Justin Meyer
http://biorxiv.org/content/early/2015/04/27/018606
(my emphasis)
I know you’re not being entirely serious, but that really isn’t a very good argument. There are plenty of reasons why a designer might build apoptosis into a body plan: scaffolding, production of metabolites for neighboring cells, it might be easier to engineer death of one of two identical progeny cells than to engineer an asymmetric cell division….. etc. The point is that once you descend into an argument about what good design might look like, you’re taking your eye off the ball, namely that all their design arguments are crap.
Just to help Nelson out, I thought I’d post a possible scenario that I’ve been pondering for evolving a worm from a single celled organism. Like Nelson, I’m an armchair biologist (not a real one) so there may be glaring problems with this. I’ve deliberately chosen an indirect method to illustrate that evolution doesn’t have to proceed in straight lines, and to keep things simple I’ve assumed all reproduction is asexual.
Step 0. We start with a single celled organism that reproduces by binary fission.
Step 1. After dividing, the cells stick together. The cells keep on dividing and adhering, producing a colonial organism of arbitrary size. Reproduction of the organism occurs by parts of it breaking off in the current and landing elsewhere to set up a new colony.
Step 2. Evolution begins exploring the possibilities for a large, multi-celled organism, such as giving it a shape such that parts of the organism protrude into the water current to collect food, and refining the shape so that water is channelled through the organism to maximize the efficiency of the protrusions. As we’ll see, the details of this aren’t important to the evolution of worms, but imagine the organism is evolving towards a filter feeder, such as a sponge or a sea squirt.
Step 3. Evolution can also streamline the reproduction process. Instead of having bits of the organism break off at random as before, it can make certain parts of itself weaker so that those parts are “deliberately” released. We’ll call these parts “spores”. There are lots of ways evolution can improve the spores so that they can reach sites further and further afield. The next few steps detail some of these improvements.
Step 4. The organism can pack the spores with nutriments, so they last longer before they settle.
Step 5. The organism can make the spores so that they have a shape which makes them drift further in the current.
Step 6. The spore can be made into a swimmer by making it move in a certain way. In our scenario, let’s suppose that the spores are given a ribbon like shape that can flex from side to side. The spore is now becoming more of a larva.
Step 7. We’ve already got a nutriment store, but it would help the spores if they could collect some supplemental food along the way, so evolution may give the spores a way of collecting and digesting food particles. This doesn’t have to be very sophisticated to start with, since we’ve got that food store, but it could become more complex over time. As it does, the spores can become less reliant on the food store, which may be reduced and eventually eliminated.
Step 8. By now, the spores themselves are pretty much fully-fledged organisms in their own right. They don’t actually need the sessile filter feeding stage of their life. Evolution can eliminate that entire life stage (look up “neoteny”), and we’re left with a fully evolved, ribbon-like swimming organism.