Review: Your Inner Fish

Your Inner Fish, hosted on PBS by fish paleontologist Neil Shubin of Tiktaalik fame, blends fishy fables with embryology, genetics, and human anatomy. Shubin mingles observable wonders of biology with evolutionary explanations for their origin. He claims the human body itself contains the evidence for evolution and that “we are, every one of us, just a jury-rigged fish.”

Building a Body

Most people are interested in how their bodies work. And people are definitely interested in why their bodies malfunction. Shubin’s three-part series appeals to this curiosity. Based on Shubin’s book of the same name, Your Inner Fish premiered on PBS this week to convince us that our bodies evolved from fish.

Recounting the tale of Tiktaalik’s discovery as if it were a suspenseful detective saga, Shubin shows viewers how he recovered this vital missing link, how he unearthed our long-lost “family member” from the Canadian Arctic, how he found the piece of the evolutionary puzzle that supposedly completes our story. Looking ahead to upcoming episodes, Your Inner Reptile and Your Inner Monkey, Shubin portrays the human body as the culmination of many steps that trace a course all the way up the evolutionary tree of life. “If you really want to see why you’re built the way you are,” he invites us, “it’s time to meet your inner fish.”

The LA Times calls Your Inner Fish a “smart human anatomy lesson.”1 However, like the new Cosmos, Your Inner Fish juxtaposes factual human anatomy with tiresome tales that misleadingly suggest Shubin’s evolutionary interpretations superimposed on the fossils, genetics, embryology, and anatomy in the episode are as trustworthy as the observational science. (Potential viewers should be warned that during the program Shubin engages in crude dialogue about human male anatomy.)

This is Tiktaalik, a flat-headed lobe-finned fish found in Devonian rock. Based on the size of the parts found, paleontologists estimate it grew up to 9 feet long. Neil Shubin and colleagues have found several such fish that had fossilized after burial beneath tons of sediment during the catastrophic upheavals of the global Flood around 4,300 years ago. Image: Eduard Solà through Wikipedia

These are photographs of Tiktaalik’s pectoral fins. This lobe-finned fish has bones in its fins in addition to rays, which all bony fish have. The rays (“alp” and “plp”) are easy to see in the photo and are attached at and below the so-called “elbow,” an arrangement that would have allowed an unimpeded range of motion at the joint. Bones are named according to the bones they would correspond to in an terrestrial vertebrate: H=humerus, U=ulna. (The bone thought to correspond to the radius, not labeled, is on the other side of the ulna. Bones thought to correspond to the wrist bones are u=ulnara and i-intermedia. Several small bones are also thought to correspond to digits are labeled r=radials. See inset for reference. The remaining bones comprise the pectoral girdle. Image: fossils—Neil Shubin et al., “The pectoral fin of Tiktaalik Rosae and the origin of the tetrapod limb,” Nature 440:6 (2006): 764-771. Illustration and legend—Devonian Times

This is a reconstruction of the salamander-like body of Ichthyostega based on fossil analysis. Though it had legs and digits, recent analysis suggests it was aquatic and could not have lifted its body up to walk on land. Image: Jennifer Clack, 2005, Tree of Life Project

This diagram shows several aquatic creatures whose fossils have been recovered from Devonian rock. Ichthyostega and Tiktaalik are discussed in the PBS program Your Inner Fish. Evolutionists believe that these animals had evolved features that qualify them as transitional forms and the ancient ancestors of humans. Image: Dave Souza through Wikipedia

The humerus, radius, and ulna are the long bones in the upper limb of humans. Distal to these are the wrist bones and the metacarpals and phalanges which comprise the hand and its digits. Corresponding bones in the forelimbs of other vertebrates are given the same names. In the case of Tiktaalik’s lobed pectoral fins, the corresponding bones are dramatically different in shape. Shubin calls this common pattern, which is what we would expect from God as our Common Designer, “One bone, two bones, lots of bones, and then digits.” Image: Wikipedia

Truth or Consequences

Is there any harm in believing evolutionary “just so stories” about our bodies? There is. Blindly accepting the evolutionary explanations for why our bodies work as they do can lead to poor medical judgment. Wrongly believing that humans are just animals that go through a fish stage in the womb has tragically led many women to destroy the human life within them. And the false belief that the human body suffers from many flaws consequent to our evolutionary heritage leads to a mistaken view of the real origin of suffering and death.

An Aquatic Tetrapod

Embarking on a search for humanity’s fishy beginnings, Shubin introduces us to Ichthyostega and to Jennifer Clack, who has done much of the research on it. Ichthyostega is an extinct four-legged aquatic animal found in Devonian rock, which by evolutionary reckoning is too old to contain amphibians. Ichthyostega’s hind limbs had five digits, but it could not make the necessary joint motions2 required to lift its body off the ground to walk on land. Clack explains, “Ichthyostega’s four limbs could push the top half of the body off the ground but the back end has got these paddle-like hind limbs which are useful in water for swimming with but on land act as stabilizers to stop the thing toppling over.”

Instead of simply viewing its anatomy at face value, Shubin assumes Ichthyostega had reached an evolutionary milestone. He says, “Anatomy of the bones suggested that this four-legged animal had just come onto land, was right at the edge of our search,” and then to launch the Tiktaalik saga explains, “but between these tetrapods and ancient fish there was still a gap spanning millions of years. If we could find an animal within that gap we’d be filling in a crucial piece of evolutionary history.”

A Fish Not out of Water

Shubin naturally spent much of the episode discussing Tiktaalik, which he found in Devonian rock deemed a little older than that in which Ichthyostega was found. Depicted walking out of the water in computer animations, Shubin opted to not discuss the anatomy needed for this feat, perhaps because Tiktaalik didn’t have it.

Despite declarations that Tiktaalik was “genuinely transitional”3 and had evolved “features contributing to the trend toward pelvic-propelled locomotion”4 across the terrestrial landscape, Shubin’s recent peer-reviewed writings do not make a case that it trotted out onto land. Among other problems, Tiktaalik, like other lobe-finned fish, lacked a sturdy connection between its pelvic and pectoral girdles—which attach to the bones in its lobed fins—and the bony vertebral column. Without such sturdy support, this enormous fish wasn’t going to walk out of the water. (Read more about it in Did Tiktaalik’s Pelvis Prepare Fish to Walk on Land?.“

Handy Connection

Rather than trying to make a case for Tiktaalik walking, Shubin asserts that the skeletal structure of its lobed fins pre-figured our own arms and hands. Dissecting a human hand and tugging on a tendon that flexes the fingers, he shows that the muscles that flex our fingers are found in the arm, where there is room for the bulky muscles needed for a strong grip. Then he shows some of the tiny muscles in the hand itself, the muscles that make the finely controlled precise movements of the fingers possible.

Having now given viewers a glimpse of God’s marvelous design for the human hand, he gives the “god” of evolution the credit. He says, “So where did this marvel of evolution come from? It clearly has deep roots in the past. And you can see evidence of that in the bones of modern creatures.” Yet this is not “clear.” He simply assumes that similar skeletal patterns—common designs—demonstrate common ancestry rather than a "Common Designer.

Shubin points out the pattern, “One bone, two bones, lots of bones, and then digits.” Anatomists generally use the same names for these bones regardless of the species in which they appear, for this is a pattern repeated in the limbs and wings of terrestrial vertebrates and birds. Our hands are connected via a group of wrist bones to a forearm containing two long bones (radius and ulna) and then to an upper arm containing a single bone (humerus).5 Shubin says the pattern was puzzling until Darwin explained, “At some time in the distant past they all shared a common ancestor that had a version of this pattern too.”

Darwin’s speculative explanation remains as imaginative today as when he thought of it. Biology reveals animals vary and reproduce within their created kinds. Biological observation is consistent with the biblical account. It only makes sense that a wise Creator, the Common Designer of all living things, would use this versatile, stable skeletal pattern in countless different kinds of creatures. Nevertheless, because the lobed fins of Tiktaalik contain bones reminiscent of this pattern, Shubin presents Tiktaalk as the evolutionary forerunner of this skeletal configuration.

Ray-finned fish do not have bones in their fins, but lobe-finned fish—including the living coelacanth, the lungfish, and Tiktaalik—have long bones in their fins. Some have just a so-called “humerus” or “femur,” and some have one or two long bones distal to these. Some even have “wrist-like” bones and digits. Tiktaalik is one of these. Yet having this skeletal pattern is not evidence for impending terrestrial evolution.

Because of the bones and muscles they contain, the lobed fins of sarcopterygians are able to move independently and powerfully, adding power and versatility to their swimming. While we cannot observe Tiktaalik’s maneuvers, the living coelacanth, which has only one long bone in each lobed fin, can even swim on its head. Flexible joints in Tiktaalik’s lobed fins would have likely made it able to whip its fins with power analogous to a well-executed hook kick. Shubin says Tiktaalik’s sturdy “shoulder” and bend at the “wrist” would have enabled it to do push-ups, but underwater push-ups would have just helped it maneuver in shallow water. Evolutionists can provide no mechanism for how such a trait could develop through random processes in the first place nor be transferred to some new and more complex terrestrially mobile kind of animal down the road. God provided each kind of animal—and human beings—with the anatomical designs needed to function in its environment, no evolution required.

Embryonic Recapitulation

Shubin presents the discredited embryonic “recapitulation theory”—the notion that embryos replay their evolutionary history—as if it were true. An embryo’s observable morphological journey to its completely developed form involves changes guided by the genetic information within that species, but evolutionary “phylogeny” would involve transformation of one kind of organism into another.

Searching for a story to fit their presuppositions, embryonic development helps evolutionists come up with a plausible sequence of changes that would be required if evolution of one kind of animal into a more complex one could occur. Yet experimental biology does not show such evolutionary transformations producing more complex, new kinds of organisms nor any genetic mechanism to make such molecules-to-man evolution possible.

Shared Genetic History or Shared Creator

Embryonic development, unlike fish-to-man evolution, is observable. Shubin takes us to a laboratory where we see how, by removing a portion of an egg’s shell, embryologists create a window to watch and manipulate chicken embryos. Transplanting embryonic tissue, for instance, can scramble signals and induce abnormal development. Scientists have learned that some of the signals that guide development come from substances that are found in many kinds of creatures. Sonic hedgehog (SHH) is one such substance.

Sonic hedgehog (SHH) is a protein that plays a role in development in many kinds of vertebrates—including fish, chickens, and people. Sonic hedgehog guides the proper formation of many sorts of structures, especially in the limbs and in the nervous system. Too much or too little SHH, Shubin pointed out, such as might occur due to a mutation in the SHH gene, can lead to the production of too many or too few digits. This portion of the program showcases what we learn from experimental science.

Then, however, Shubin makes another insupportable evolutionary leap, saying, “It’s clear we have a shared genetic history with fish.” But all that is clear is that SHH is a signal guiding development of many different sorts of tissues in many different kinds of animals. SHH influences wing development in chickens, fin development in fish, and finger development in people. SHH is one of many universal switching mechanisms that our Creator uses in many of His creations. Nothing about it demonstrates “a shared genetic history,” but it is exactly what we would expect from the fact that we have a “shared Creator.”

Gills On People?

Pharyngeal arches in human embryos become parts of the jaw, face, ear, middle ear bones, and voice box.

Your Inner Fish also promotes the myth of embryonic recapitulation by showing us “Molly’s gill.” Molly is a woman with a small pit in front of her ear, an inconsequential embryologic remnant that Shubin identifies as “a leftover from an ancient gill” saying, “We’re all fish,” and “Sometimes things go wrong, and when they do your inner fish can come out.”

Vertebrate embryos have several swellings along the neck, little mounds of cells that are multiplying and differentiating into the structures blueprinted for them in the organism’s DNA. Based on superficial appearance and evolutionary thinking, they were once called things like gill slits, gill pouches, gill arches, or branchial arches. Only in fish do these arches differentiate into components of gills. Many embryology textbooks have abandoned this deceptive terminology in favor of pharyngeal arches, for mammalian embryos never at any time develop any sort of gill. Pharyngeal arches in human embryos become parts of the jaw, face, ear, middle ear bones, and voice box. We can speak, hear, chew, and smile because of complex array of structures these pharyngeal arches form. Nevertheless, Shubin calls them “gill arches” and gives Molly an imaginative evolutionary explanation rather than an embryologic one. Molly's pre-auricular pit is a tiny remnant that was left over when parts of the first and second pharyngeal arches fused to form her ear, but neither Molly nor her ancestors ever had a gill.

Flaws That “Prove” You Are “Just a Jury-Rigged Fish”?

Half the human population—the male half—is at risk for developing inguinal hernias.6 The tough lining of the abdominal wall folds back in on itself just above the thighs, forming an enclosure for the abdominal organs. The gonads of most male mammals (including humans) form inside the body and during development descend through this fold into a position outside the body. The weakness that occasionally develops in this fold is called a hernia. The reason men are more likely to develop such a hernia involves embryology, not evolution. Shubin disagrees. He and a friend gut a fish to show us that fish gonads are located inside the body and then spins the evolutionary tale that evolving into warm-blooded animals necessitated the translocation of the gonads to the cooler location outside the body where sperm production is better. He concludes:

Flaws in the human body, like our susceptibility to hernias, remind us that we’re all adapted from ancient ancestors; we are, every one of us, just a jury-rigged fish.

There are several problems with this statement. First of all, is this really a design flaw? The external location of the human male gonads is ideally suited for the heat-sensitive sperm they produce. A muscle is able to adjust their precise location in response to outside temperature. And as sperm travel a circuitous path to the outside of the body they are enriched with a number of vital secretions and substances essential to their function. This arrangement is a well-engineered design, from the point of view of optimizing fertility.

There is an additional problem with Shubin’s convenient evolutionary explanation. Not all mammals follow the path he laid out for them. For instance, the rhinoceros seems to be quite fertile despite the internal location of its gonads.

But what about those pesky hernias? God designed a perfect human body along with a perfect world in the beginning. How do we know? He told us so in Genesis 1:31. And God warned Adam that rebellion would have consequences (Genesis 2:16–17). Adam did rebel and ever since that day the entire world has groaned (Romans 8:22) under sin’s curse. People’s bodies have worn down, gotten ill, and died. The problem is neither bad design nor evolutionary bondage, but the perversion of God’s good original designs as a consequence of man’s rebellion against the Creator. We should be thankful that our bodies work as well as they do and that embryologic development usually operates as it should. Anyone who has studied human anatomy and physiology without evolutionary presuppositions—as I, a physician, have been privileged to do—should not recognize our “inner fish” but instead the hand of the Master Designer, our Creator and Savior Jesus Christ (Colossians 1:16–17), and with the psalmist declare we are “fearfully and wonderfully made” (Psalm 139:14).