Horseshoes and Crab Legs: New Evolutionary Angles

If a horseshoe crab is neither horse nor crab, what is an evolutionary explanation?

Horseshoe crabs are prime examples of “living fossils” that have evolved little since their appearance in the fossil record hundreds of millions of years ago,* but now some evolutionary paleontologists want to shout that a fossil horseshoe crab “illuminates the evolution of arthropod limbs.”  Indeed, Derek Briggs and his Yale gang, publishing in PNAS ( September 11, 2012, doi: 10.1073/pnas.1205875109), are convinced that we can all learn oodles of wisdom by observing that some relatives had single legs and others had split legs.  Of less concern to them is why horseshoe crabs (Limulus) remained basically unchanged for 445 million years (or more, if Cambrian arthropods with similar body plans are considered).  Joined or single limbs might seem minor compared to eyes, guts, muscles, nerves, sexual organs and all the other complex features of these enduring animals that appear abruptly in the fossil record.

PhysOrg jumped right on the evolutionary bandwagon, posting the Yale press release uncritically and with a jazz riff by Briggs himself:

“This fossil provides remarkable confirmation of the loss of a limb branch during horseshoe crab evolution, a change predicted by the common presence of two branches in the arthropods that appeared earlier, during the Cambrian explosion,” said Derek E. G. Briggs, director of the Yale Peabody Museum of Natural History and lead author of a paper to be published online the week of Sept. 10 in the journal PNAS. The fossil dates from the Silurian period, about 425 million years ago.

What apparently was not as remarkable to Briggs was that this creature, threatened by man today, survived all the major mass extinctions that wiped out 90% of organisms in the Permian and all the dinosaurs in the Cretaceous, and other mass extinctions in the evolutionary timeline.  Yet somehow it never evolved much in far more Darwin Years than it took for cows to become whales and chimps to become humans.  Evolution works in strange ways.

What in particular “illuminates the evolution” in this fossil?  PhysOrg was just thrilled to explain, it’s “the evolution of these ancient arthropods—the transformation of two-branched legs into nearly identical but separately attached limbs, one of which was destined to disappear.”  Oh.  Interesting.

Speaking of disappearance, one poor little Limulus recorded its “death march” in stone, BBC News said.  The last drunken walk of this creature, asphyxiating in a lagoon lacking oxygen, was revealed in stunning clarity in Lagerstaette (fossil beds of exquisite preservation) on the England-Wales border, “a site rich in well preserved, soft-bodied fossils,” according to PhysOrg.  If you want to follow its death march, Live Science in its coverage added a photo gallery to help you pity the creature’s last gasp.  Since this was a death story, none of these articles mentioned the e-word evolution.  Remarkable how identical the critter looks to living horseshoe crabs after 150 million years.

Speaking of crab legs (although Limulus is not a crab), another article about legs shows how no matter what observations the evolutionists have to concede, they play the victor.  Intelligent design is their straw man to knock down without debate.  PhysOrg posted a press release from the University of Dublin asking a design question then immediately throwing the score to Darwin: “Are our bones well designed? Insects and crabs have a leg up on us.”  Even though this would seem a foul for Darwin, since humans are further along the evolutionary ladder, the deceptive play apparently fooled the referee:

“Like all Arthropods, grasshoppers and crabs have so called exoskeletons made from a very special material called cuticle,” said Professor David Taylor, of the Trinity Centre for Bioengineering at Trinity College Dublin, Ireland. “This exoskeleton protects the animal like a knight’s suit of armour. Recently we have shown that this cuticle is in fact one of the toughest natural materials.“

“In terms of evolution, having your bones on the outside has been a pretty good concept,” said his colleague Dr Jan-Henning Dirks. “Since millions of years animals with exoskeletons such as insects, spiders and crustaceans can be found basically in every ecosystem in the world.“

The article went on and on about how fine exoskeletons are.  My, why would evolution throw out such a “good concept” (don’t say “design”) when it came to mammals?  The reason the Darwin Team scored on this one is that the judges are Darwinians, too.   The fighting Irish even presumed to play intelligent designer, just for the irony of it: “Using the same amount of bone material and taking into account its mechanical properties, the human thighbone could be ‘redesigned’ as an exoskeleton to be twice as strong as it is now.”

Then, unfortunately, Taylor fouled out by using the d-word design in the same sentence with the e-word, thus winning Stupid Evolution Quote of the Week:

“Of course there are numerous other factors determining the evolutionary advantages of endo- and exoskeletons,” said Taylor. “However, we think that by taking a design engineer’s view on the problem we’ve been able to shed some light on the evolutionary development of skeletal forms.”

* “Horseshoe crabs are often referred to as living fossils, as they have changed little in the last 445 million years” (Wikipedia).

More evidence that Darwinism is going to be viewed someday as the funniest losing act in the show, “Science’s Got Talent.”    You don’t have to wait for the audience to get the joke.  If you laugh out loud now, you might start something like the wave at a football stadium, initiating what everybody wanted to do anyway, but were afraid to start.  Even the Darwin-leaning judges will have a hard time letting the act continue if the whole audience is yucking it up hysterically.