lpetrich

That's his most recent book, coming after Crucible of Creation. I have not had much of a chance to read either book, but I've seen plenty of discussion of their contents, like at pharyngula.org and elsewhere.

Simon Conway Morris has a grudge against Stephen Jay Gould, which he expresses in Crucible of Creation. Of course, it did not help SJG that he had used the upside-down reconstruction of Hallucigenia in Wonderful Life.

And he tries to argue in Life's Solution that life emerged nowhere but on Earth -- and that humanity's appearance was inevitable. I find both hypotheses very improbable.

Although the origin of life is far from a solved problem, hints of a solution are gradually emerging from studies of both prebiotic chemistry and very early evolution.

SCM's main argument for the inevitability of humanity is a rather weak one: the abundance of convergent evolution. I call it weak because convergence sometimes does not go as far as necessary. Consider a feature that is likely necessary for becoming a land animal much larger than 10 cm or so: an internal bony skeleton. Bone is strong enough to carry the weight of even the largest dinosaurs, and being internal, it is right where it is needed, in contrast to shells. It is also not molted, meaning that it does not have an important limiting factor of the arthropod skeleton. Right after molting, an arthropod is soft and vulnerable. The arthropod skeleton also shares with the echinoderm skeleton the disadvantage of being spread over the body's area, instead of being concentrated in rods and such; this can add a lot of bone weight. Turtles have converged on having such a bony external skeleton, and though some turtles have grown very large, land turtles are usually very slow.

But a bony internal skeleton was invented only once, being only one of several skeletal solutions used by the Earth's metazoans.

So if that was never invented, we could never have come into existence on this planet.

Another possible bottleneck is the development of limb extremities (1) specialized for grasping, preferably with opposable digits, and (2) available for manipulation of objects. This has been very rare among land vertebrates. Birds often satisfy (1) with perching feet, but their placement does not satisfy (2). Primates have also invented grasping extremities, but on all four limbs, making possible (2) and well as (1), as our species and chimps so abundantly demonstrate. In fact, the evolution of hominid bipedalism may have been correlated with increased use of hands for carrying and otherwise manipulating objects (there is a lot of argument about the direction of causality here).

Turning to other land vertebrates, kangaroos' front feet appear to be un-adapted for grasping, resembling their hind feet. Birds' front limbs are specialized as wings, and making them grasping limbs would require a lot of evolutionary remodeling. But could their Mesozoic ancestors, the theropod dinosaurs, have included some species with grasping-adapted front limbs?

pz

I also sniped at him before.

I found Life's Solution truly awful. His arguments were pathetic and selective, and throughout it was clear that he was operating from a religious motive: he had a predetermined idea of what result he wanted, and was juggling the evidence to support that preconception. It was a disgraceful betrayal of the scientific ideal.

I predict this book will be extremely popular with intelligent design creationists. I could tell he was just itching, in his section on the improbability of the origin of life, to declare a miracle. The IDCs will be less reticent.

lpetrich

A more reasonable approach would be to make a checklist of features and then to check on how easily "evolvable" they are.

Jawlike structures are easily evolvable, because they have emerged several times -- vertebrate jaws, insect/crustacean mouthparts, squid/octopus beaks, etc.

Likewise, air breathing has evolved several times -- ancestral bony fish whose lungs usually became swim bladders, walking catfish (Clarias), insects, isopods (pillbugs/sowbugs/woodlice), land crabs, arachnids, myriapods (either once or centipedes and millipedes separately), and land snails (prosobranchs and pulmonates possibly separately).

However, a vertebrate-style internal skeleton has evolved only once, while external skeletons and shells have evolved several times. So one may reasonably conclude that such an internal skeleton is more difficult to evolve than an external one.

Nic Tamzek

Hidey ho,

FWIW, I haven't yet read Conway Morris's Life's Solution.

(BTW, is it not true that Simon Conway Morris's last name is "Conway Morris", sort of like John Maynard Smith is referred to as "Maynard Smith", as in "Maynard Smith, John". Some sort of British thing or something?)

I will therefore refrain from commenting except to say that a priori, I don't find the postulate that evolution has a significant propensity to converge on humanlike critters particularly compelling. Compelling convergences are things like hydrodynamic shape (dolphins-icthyosaurs-fish), eyes (the usual), flagella (archaeal and bacterial flagella) and pitcher plants (my personal favorite). I do think that one could argue that things like a reasonable level of intelligence (the dog-octopus-cuttlefish-dolphin-monkey level), a high degree of sociality (common lots of places), and crude tool use (several instances) are reasonably common convergences. One might *then* be able to argue that sooner or later these features would get combined and that such a lineage would have an increased chance of producing a fully sentient critter. But these last few steps are much weaker than the more general convergences.

But, getting to a book I have read, Crucible of Life, I think PZ et al. are being way too hard on Conway Morris. I did not see it as a fire-breathing attack on Gould, I don't see how anyone could. Compared to, say, the things that Dawkins or someone says about Gould it was rather tame. Why shouldn't Conway Morris critique Gould, since Gould got a hugely popular book (Wonderful Life, strongly promoting the Gouldian "contingency" worldview, out of Conway Morris's studies? And frankly, there are a lot of valid criticisms of Gould along the lines of "Gould proclaims revolutions but upon investigation there ain't much there".

Furthermore, Gould favored a view of the Cambrian fauna that matched up with his punctuated equilibrium rhetoric (if not with the actual punctuated equilibrium theory, which was about allopatric speciation and not, really, about higher-level taxonomic categories). This view was one with new phyla popping up everywhere in the Cambrian "Explosion", without precursors or close relatives. You will recall the mileage that creationists attempted, and still attempt, to get out of this. One of Conway Morris's main points is that this viewpoint is a combination of taxonomic artefact (creating new phyla for taxonomic convenience, creating an illusion of radical morphological disparity), misinterpretation of fossils (many thought originally to be bizarre have now been allied to traditional groups), and the effects of the evolution of hard body parts on (1) fossilization potential and (2) adaptive radiation (predator-prey arms races).

In other words, Conway Morris brings the Cambrian "Explosion" into the fold as pretty much another fairly normal evolutionary event, rather than as something extraordinary. IMO this is a significant acheivement.

Sure, Conway Morris's personal theology may color his interpretations somewhat, but Gould pretty clearly has committed the same sin. And when it comes to the Cambrian, Conway Morris is a primary expert, while Gould is an outsider (though very well informed).

I will grant that Conway Morris is not much of a writer compared to Gould. But heck, who wants their writing ability compared to S.J. Gould?

pz

Yes.
I agree about Crucible of Life. It's written in the deadest, most painful prose, but Conway Morris is a smart guy and the authority on the material, and it's definitely worthwhile as a counterbalance to Gould (although I ultimately think there is value in both perspectives). Because Conway Morris really does have the goods, I felt compelled to read Life's Solution even though the reviews and summaries were omens of doom.

Unlike Crucible of Life, though, Life's Solution doesn't build from Conway Morris's strengths as a paleontologist. It's driven by his religion rather than his evidence, and is about as unscientific a pile of BS as I've seen come from the hand of a eminently qualified and respected scientist -- Conway Morris seems to be aspiring to Fred Hoyle's reputation.

Crucible of Life is sitting on my bookshelf next to Wonderful Life, with the good stuff. Life's Solution is getting stashed way down on the end, with the collection of creationist aberrations and curiousities.