Caribbean Reef Squid: A Conundrum for Neo-Darwinian Evolution?

Photo: Dan Hershman

Photo: Dan Hershman

My all-time favorite form of recreation is coral reef snorkeling. For me, there is NOTHING that compares to the thrill and wonder of floating above a spectacular reef, observing all of the colorful sea life that dwell in and around it. I recently visited reefs in the Virgin Islands, where I encountered beautiful creatures such as parrot fish, butterfly fish, needle fish, and a rainbow variety of corals. I was once again struck by the magnificence of God’s underwater creation. How could any intelligent person believe such wondrous living beauty and symbiosis came about without conscious foresight and design? But many (though not all) working in the field of evolutionary biology believe exactly that. They place their faith in the assumed capabilities of the engine of natural selection.

In this post, I would like to profile just one marine animal capability that, I believe, demonstrates  a serious explanatory handicap for Neo-Darwinian evolution.

The Engine of Natural Selection

In his famous tome, On the Origin of Species, Charles Darwin offered a caveat to his theory of species divergence through natural selection:

If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down. But I can find out no such case. (p. 348)

In the century and a half since Darwin penned these words, knowledge of the botanical and zoological world has increased exponentially. Field biologists have observed and recorded astounding phenomena that Darwin could never have dreamed of. Great strides have been made in elucidating the physiology of particular phenomena, but accounts of their evolutionary origin remain sorely lacking in explanatory scope and sufficiency. There are some phenomena that, because of their very nature, present significant obstacles to Neo-Darwinian explanation. (By Neo-Darwinian I mean an unguided, undesigned, aimless  process of evolution.)

A spectacular example of a creature that seems to utterly defy naturalistic explanation is the Caribbean reef squid, known by the scientific name, Loliginidae sepioteuthis. These highly intelligent cephalopods (the broader animal category that includes squid, octopuses, and cuttlefish) utilize a stunningly sophisticated mode of communication that is based upon lightening-fast changes in the colors, patterns, and textures they exhibit in their skin. The squid have dynamic structures in their skin called chromatophores that are used to cause these changes. The squid also has special structures that reflect or absorb incoming sunlight to help form all the various skin colors and patterns. The iridescent areas are called iridophores.

Chromatophores and Iridophores

Here’s a diagram of the chromatophore and the associated muscles (15-25 of them) and nerve endings that make it operational:

Diagram by Cloney, R. A. and E. Florey. 1968.

In less than 30 milliseconds (yes, milliseconds!!),  and in response to a visual cue, the squid can purposefully change its color and pattern to communicate with another squid, court another squid, stun their prey, or to try and ward off or confuse a potential predator. Many of the color/pattern displays include certain arm postures, as well. The squid can manipulate its color/pattern display in order to make it appear to move across their body.

Even more astounding is the fact that the squid can communicate two different messages to two different squid at the same timeCheck out the 8th photo on this website. The squid in the center is communicating one thing to the squid on his right, and something entirely different to the squid on his left! See how his color and pattern are split right down the center?

Here’s a cool video that shows squid communication in action:

ARKive video - Caribbean reef squid changing colour


More stunning reef squid photos can be viewed here:

ARKive photo - Caribbean reef squid undulating fins

So, what we have here is an animal with:

1) a highly complex eye that can focus on shades and patterns

2) a nerve network that includes a brain able to process visual cues (such as the approach of a predator or the presence of other squid) and translate them to the necessary skin structures

3) muscle-controlled pigment structures in the skin which can be purposefully manipulated by the squid in a large variety of ways to produce and change colors, reflections, and patterns in a tiny fraction of a second, even for producing two signals at once, each to a different squid


4) the cognitive ability to interpret and respond to the signals when they are sent by another squid

What does Neo-Darwinian theory have to say about the evolution of this elegant, intricate system?

Dr. James Wood, a scientist who has extensively studied cephalopods, says that these concerted abilities of the squid have “evolved through adaptation and natural selection over time.” (1) He says:

Instead of heavy armor, [squid] rely on speed and visual tricks to avoid being eaten. Some scientists have suggested that these adaptations were in response to pressure from predators. Indeed, many of the tricks such as the ability to change color, shape and texture…seem to be aimed directly at their predators. (2)

Indeed, for at least 40 years now, scientists have believed that the skin displays developed primarily for camouflage. Byrne (et al) assert that:

The flexibility of the chromatophore system and its speed of change lend themself [sic] ideally to communication purposes, therefore it is not surprising that cephalopods evolved intraspecific communication signals with this system. (3)

Oller and Griebel, in their book, The Evolution of Communication Systems: A Comparative Approach (p. 197), say that “cephalopods appear to have adapted the particular characteristics of a system designed for one purpose to another: communication to conspecifics” (conspecific means a member of one’s own species).

Okay, let’s consider that possibility. Going back to Darwin’s statement, which reflects a fundamental idea behind modern evolutionary theory (slight, successive modifications that each impart survival advantage), can we construct a feasible naturalistic scenario for the emergence of the squid communication phenomena? In other words, could natural selection acting upon random genetic mutations have produced what we observe in the squid?

Photo: Nick HobgoodWikimedia Commons

Photo: Nick Hobgood

The Caribbean Reef Squid Stalls the Engine

Suppose we have a primitive precursor to Loliginidae sepioteuthis. This hypothetical squid has no chromatophores in his skin, nor does he have the associated muscles, nerve network, or brain structures necessary for communication. Eventually, this squid reproduces, and a random, spontaneous mutation causes one of his offspring to have spots of darker skin pigmentation that make it more difficult for predators to detect him. Okay, good! This is a survival advantage, so it will likely be passed on and preserved through natural selection. That is completely reasonable. But the squid is still a very far cry from having the intricate system we need him to obtain. He must evolve much, much further and in a myriad of ways.

This is the point where things become highly problematic for Darwin’s “successive, slight modifications.” First of all, we need more spontaneous mutations that will cooperate with what we already have (dark skin spots). How about the muscles for expanding and contracting the pigmented spots? Unfortunately, a mutation that produces a muscle or two (or three, or four) around the pigmented area is essentially useless, because we still need (among other things) the associated nerves to control the muscles and the brain wiring for moderating the neurotransmitters (chemicals that activate nerves) and for processing sensory input.

What would be needed here is a multitude of synchronized genetic mutations that bring about an interconnected set of new features if the squid is to gain beneficial functionality. For the communication capability observed in the squid, dark spots alone are worthless (aside from camouflage), and other parts of the communication system would be equally worthless if they appeared alone. Why would the squid need spot-manipulating muscles without the spots, or the ability to release neurotransmitters in response to visual cues if the chromatophores were absent? What we have here is a system that has numerous necessary parts. Remember, the evolutionary scenario depends upon random beneficial mutations for natural selection to have anything at all to work with. Not only do we need mutations to build the squid communication phenomena, we need many mutations in different parts of the squid genome, and we need them to happen together so that they actually create a new, useful function. What’s more, we need mutations that enable the squid to process the signals transmitted by other squid.

Not only is the idea of all of these complimentary, synergistic mutations happening around the same time vastly improbable, what we know about the rate of genetic mutation and the available time since squid first appeared in nature indicates that there simply hasn’t been enough time for the estimated number of specific mutations involved to occur and become fixed in a population.

Neo-Darwinists have concocted various theories to try and get around these problems, which, by the way, are not unique to the origin of squid signaling. [It should be emphasized that I am specifically talking about UNGUIDED macro-evolution here; the same problems do not arise for the theory of intelligence-guided evolution.] Sometimes, evolutionary biologists will suggest that neutral mutations accumulated over time and eventually began working together in an advantageous manner (Dr. Michael Ruse likes this argument, which he details in his book, Darwin and Design). However, from work done in the laboratory using bacterial populations, it has been observed that the accumulation of neutral mutations is severely limited.

Another tactic is to postulate that random mutations imparted some other, unrelated survival advantage, and eventually, when many such mutations were all ensconced within the organism’s genome, they were commandeered (“co-opted”) to form a new functional system (Dr. Kenneth Miller favors this story).

To say that these explanations stretch the bounds of credulity is an understatement. But in the world of naturalistic evolutionary biology, the “fact” of unguided evolution is automatically assumed, despite the insurmountable problems many complexities pose for the paradigm. The “how” is just a minor detail. (For some insightful comments on this, see the recent article by James Tour of Rice University.)

In everyday life, whenever we encounter coordinated systems with many necessary parts that work in concert to produce outcomes appropriate to the setting, we immediately recognize the planning and design of an intelligent engineer. By analogy, we can and should recognize such design in the systems required to produce intricate, systematized biological phenomena, such as the amazing communication abilities of the Caribbean reef squid.


Photo: Clark Anderson




Photography obtained through Wikimedia Commons. Chromatophore/Iridophore photo by Minette on Wikimedia Commons. Please note that the photographers in no way endorse the content of this website.