The Evolution of the Darwin Fish

The Darwin Fish scientific method: Draw a fish. Draw legs on it to mock Christians who use it as a symbol. Then furiously hunt for evidence that a fish with feet existed.

Darwinians believe that fish crawled out onto land—their fins becoming pentadactyl limbs—then returned back to the sea multiple times in the form of ichthyosaurs, pinnipeds and whales. The belief came prior to any evidence for fish with feet, because Darwin complained about the lack of transitional forms in his Origin of Species. He knew that most species appear abruptly in the rocks, and that his needed transitional forms were not found: “Geology assuredly does not reveal any such finely graduated organic chain; and this, perhaps, is the most obvious and gravest objection which can be urged against my theory,” he said (Origin 6th ed., p. 280). He did not, therefore, even speculate about how fish evolved into land creatures, although he hoped that transitional fossils would turn up some day.

Sign at Wyoming Dinosaur Center, “Our evolving understanding,” debunking earlier ideas about tetrapod evolution, before claiming Tiktaalik to be a “Fishapod” candidate. Photo by David Coppedge.

Tiktaalik model exhibited as “Fishapod” at Wyoming Dinosaur Center. Photo by David Coppedge.

After Darwin, various ‘transitional’ fish with bony fins were subsequently proposed and deposed (see sign, above), but Darwinians didn’t become excited until Neil Shubin’s Tiktaalik fossil (6 April 2006), though some disagreed (4 December 2008). Tiktaalik, though, was discovered long after the ‘Darwin Fish’ symbol had become a cultural icon on bumper stickers and office doors. Subsequently, though, tetrapod tracks were found a full 10 million Darwin Years earlier (6 January 2010), undermining Shubin’s claim to have found a transitional form.

Darwinians are still hunting. Some of their claims seem outlandish (if you’ll pardon the pun). Who would think that rays and skates would be candidates? Sharks and rays—cartilaginous fish—don’t look ready to crawl onto the land. Science Daily, though, jumps on a new idea coming out of the New York University School of Medicine: “Walking fish suggests locomotion control evolved much earlier than thought.” [Thought by whom? See tontology.]

Cartoons that illustrate evolution depict early vertebrates generating primordial limbs as they move onto land for the first time. But new findings indicate that some of these first ambulatory creatures may have stayed under water, spawning descendants that today exhibit walking behavior on the ocean floor. The results appear February 8 in the journal Cell.

“It has generally been thought that the ability to walk is something that evolved as vertebrates transitioned from sea to land,” says senior author Jeremy Dasen, a developmental neurobiologist in the Department of Neuroscience and Physiology at the New York University School of Medicine. “We were surprised to learn that certain species of fish also can walk. In addition, they use a neural and genetic developmental program that is almost identical to the one used by higher vertebrates, including humans.“

National Geographic leapt onto that suggestion of a human connection, headlining, “Walking Skates Can Teach Us About Human Evolution.” To see what this “walking” behavior looks like, see the video on Nature News, “Primitive fish’s sea-floor shuffle illuminates the origins of walking.” How can a living fish be called ‘primitive’ if it has been successful for hundreds of millions of Darwin Years?

The embryonic skate’s two hind fins perform a back-and-forth motion that partially resembles walking. These motions appear during a developmental stage when neural circuits are forming (a process known in almost all vertebrates and invertebrates). The trouble is, the fins in the skate are not limbs. They do not have the bones and muscles of terrestrial legs. The resemblance is only superficial. Nature admits, “how skates and humans evolved the ability to walk on two limbs is still a mystery.”

Three Darwin Fish on an office door at JPL, 2010. Photo by David Coppedge

There are several other problems with the story:

• Skates are only distantly related to mammals, according to evolutionary phylogeny.
• The adaptation appeared 20 million Darwin Years before the first alleged tetrapod.
• The adaptation would have appeared in the sea for a non-terrestrial purpose.
• The skates still live today like this, not having progressed into terrestrial animals.
• The skate motion only involves six muscle groups per fin. Mammals “use hundreds of muscles to move.”
• To be consistent, every creature with a back-and-forth movement would have to be promoted to transitional form, making the concept vacuous.

Additionally, Nature says, “The findings suggest that the nerve cells essential for walking evolved millions of years earlier than previously thought.” It’s hard to see how that “helps scientists develop a more complete understanding of our prehistoric common ancestor,” as National Geographic boasts. For these and other reasons,

some researchers urge caution when interpreting the results. “We must be very careful about looking at any living group and thinking it represents ancestral conditions,” says Michael Coates, an evolutionary biologist at the University of Chicago in Illinois. To confirm that the common ancestor of skates and humans had a set of genes and nerve cells for walking, the team should analyse a larger sample of animals, including fish that are more closely related to mammals, he says.

A Cornell evolutionist uses the occasion to demote human exceptionalism:

“This study is the first deep foray into the origins of limb-control circuits,” says neuroscientist Joseph Fetcho of Cornell University in Ithaca, New York. There are some fish species that are more closely related to mammals that can walk on the sea floor. But it’s “really cool” that skates, which are relatively primitive, are able to move their limbs in the same way as people do, Fetcho says. “We’re not as special as we think we are.”

The finding could help, though, in non-Darwinian ways: “Understanding the foundational genetics of motor movements also has medical implications down the line.” If so, it has nothing to do with Darwinian evolution. It just means we would understand the connection between observed genetics and observed movements in different organisms. Intelligent design advocates could take the same observations and advance understanding by predicting that the systems are not accidental, but exist for a purpose. Knowing how purpose has been instantiated in animals could lead to advances in biomimetics as well as in medicine.

Quick! Evolve or Perish!

Ephemeral waterpockets after rain, Canyonlands. Photo by David Coppedge.

An even less empirical story was posted by Nature News: “Ocean tides could have driven ancient fish to walk” (emphasis on could, a key perhapsimaybecouldness index indicator). According to this tale, fish had no other option than to walk away. “Evolution of land-walking animals may have started with fish that were stranded in tidal pools.”

If this were a law of nature, we should see it happening now. Thousands of vernal pools and potholes exist throughout the world, where tiny creatures (such as frogs, fairy shrimp and insects) live out their brief lives after rains, then lay eggs before the pool dries up for the summer. A billion natural experiments should support the idea that stranded animals can evolve legs and even wings to escape their natural traps.

“The idea that the first land-walking animals could have evolved from those stranded in tide pools is generally well accepted and dates back decades,” Nature claims, employing a  bandwagon argument. Alexandra Witze, strangely, tries to keep both Tiktaalik and the Polish trackways happy companions in the Darwin (or rather Lamarckian) scenario:

The team speculates that fish that could have made their way out of the tide pool, and back to the water, would have been more likely to survive. Fossils of some of the earliest known terrestrial tetrapods, such as the Tiktaalik lobe-finned fish from Canada’s Ellesmere Island and trackways in Poland’s Holy Cross mountains, have been found in places that had these high tidal variations.

The last two paragraphs, however, undermine the claim:

Some researchers are sceptical about the idea, however. “It’s only one of a plethora of ideas for the origin of land-dwelling tetrapods, any or all of which may have been a part of the answer,” says Jennifer Clack, a palaeontologist at the University of Cambridge, UK.

Matthew Huber, a palaeoclimate modeller at Purdue University in West Lafayette, Indiana, would like to see more evidence that the correlation between the timing of large tidal ranges and the evolution of animals that walked on land isn’t a coincidence.

Huber’s final sentences demonstrate how evolutionists are reluctant to call other evolututionists’  ideas crazy. “But the work is intriguing, he says: “The connection seems worth pursuing.”

Yes! Keep pursuing just-so stories until you hoodwink the public more effectively! Good grief. If this were a law of nature, ocean tides “could” drive humans to evolve surfboards for feet, and dust devils could drive lizards to evolve powered flight. Why aren’t more people laughing?