Brains first make their appearance in the Cambrian explosion. Beware, your own brain may explode when you hear how Darwin defenders explain their origin.
Consider for a moment how complex even a simple brain is. A single neuron is very complex, lined with precision sodium channels that “fire” in sequence down an axon or dendrite. At the tip, vesicles carry complex chemical neurotransmitters across a gap, or synapse. But a single neuron is useless alone; it needs a network of other neurons to communicate information. That information must be processed by some kind of central nervous system, which must be able to interpret the information and respond by commanding other specialized tissues, such as muscles. The earliest Cambrian animals possessed brains that could operate numerous complex systems: sensory organs, digestive systems, articulated limbs, sexual organs and complex behaviors. Those things were lacking in their Precambrian predecessors, the Ediacarans.
Current Biology this month has a special section on the origin of brains. The authors commit the same blunders we saw just days ago: (1) they appeal only to unguided natural processes, (2) they rely on magic words, and (3) they ignore arguments and evidence for design of the type Stephen Meyer presents in Darwin’s Doubt. Brains just explode into existence — no intelligence required!
Name It and Claim It
In “The Basal Ganglia Over 500 Million Years,” in Current Biology, Grillner and Robertson have this to say:
Cyclostomes have evolved separately from mammals over more than 500 million years. It follows that when detailed similarities are demonstrated between forebrain circuits in the lampreys of today and those of mammals, these circuits were most likely already present at the dawn of vertebrate evolution (Figure 1). This was at the time of the Cambrian explosion when fossil records show the appearance of a multitude of now extinct species, but also the origin of different extant phyla like arthropods and molluscs, as well as vertebrates (cyclostomes). At this time, many of the molecular components of nerve cells had been designed (through evolution), including most ion channels, transmitters, and ionotropic and metabotropic receptors. [Emphasis added.]
This kind of language conceals rather than enlightens. The authors simply assume evolution: “Cyclostomes [’round mouths’ or jawless fish] have evolved,” they assert, demanding unquestioned affirmation. They refer to “the appearance of” and “the origin of” complex animals without asking how that happened. Then they present a list of complex machinery involved in brain cells, informing us that at the very time all the animal phyla abruptly appeared, these things “had been designed (through evolution).” It’s enough to make your brain hurt.
The Arthropod Circus Cannon
Strausfeld, Ma, and Edgecombe recount the greatest show on earth, the Arthropod Cannon. Practice your most exuberant P.T. Barnum impression on the last clause in this excerpt from “Fossils and the Evolution of the Arthropod Brain” in Current Biology:
Recent phylogenies of the arthropods, based on fossil and molecular evidence, and estimates of divergence dates, suggest that neural ground patterns characterizing onychophorans, chelicerates and mandibulates are likely to have diverged between the terminal Ediacaran and earliest Cambrian, heralding the exuberant diversification of body forms that account for the Cambrian Explosion.
They don’t let us peek inside the cannon. All we see is the explosive appearance of central nervous systems in all three branches of arthropods after the explosion. But what happened inside the barrel? The story requires a leap of faith.
The oldest body fossils of euarthropods [true arthropods] date to the second of four series into which the Cambrian is divided, coincident with the first appearance of trilobites around 521 million years ago. This almost certainly underestimates the antiquity of euarthropods based on two lines of evidence: trace fossils and molecular dating. Rusophychus traces, excavations interpreted as having been made by the jointed appendages of euarthropods, first appear close to the base of the Cambrian in many parts of the world, and Fortunian (earliest Cambrian) sediments include other euarthropod traces, such as Diplichnites, Monomorphichnus and Cruziana. The trace fossils (Figure 1A,B) thus predate the body fossil record of euarthropods but yield no evidence for Ediacaran (> 541 million year old) arthropods. On the contrary, it suggests that euarthropods first diversified in the early Cambrian.
But the fossils shown in Figure 1 are not much help. It takes a lively imagination to see arthropod traces in the squiggly lines on a flat surface of rock they say dates from late Ediacaran. The first true arthropod fossils at the base of the Cambrian “had exoskeletons, were highly motile and exploited three-dimensional space,” they note. By the time the Burgess Shale was deposited, Cambrian arthropods had a “brain, optic lobes…, prominent eyes and a triplet of ocelli.” Since the fossils don’t show the transition, they place some hope in molecular dating. We’ve explained why the molecular clock is untrustworthy. These authors concur that “molecular dating yields substantially different estimates for the dates of divergence” for different groups, but they choose to believe that the divergence had to take place earlier, based on “the most recent studies” cited in 2013 and 2014, written before the 2015 paper that we reported shows the molecular clock is broken.
The other five Figures in the paper show fully developed, complex central nervous systems capable of operating articulated limbs, eyes, muscles, digestive systems and complex behaviors. Most interesting is the early Cambrian animal Fuxianhuia protensa, which Casey Luskin wrote about. He quoted Nature calling its brain “a very modern brain in an ancient animal.” That was in 2012. These authors, describing it in 2016, say, “Fuxianhuia may have been an active predator requiring considerable brain power.” Brains are exploding all over the place.
Because We Say So
Hardcastle and Krapp are fond of saying that complex things “have evolved.” We count ten instances in their Current Biology piece about “The Evolution of Biological Image Stabilization.”
- “No matter how simple or sophisticated the eye design, mechanisms have evolved across phyla to stabilize gaze.”
- “Here, we present a few examples which illustrate the general principles of how, and why, visual animals stabilize their gaze relative to the world they live in, and some of the species-specific adaptations of the sensory and motor systems which have evolved to support a level gaze.”
- “As described by Land in a recent review, areas of high spatial resolution have evolved independently of phylogenetic age in various phyla, and are found in aquatic, terrestrial and aerial animals alike.”
- “Animals and their sensory systems have evolved under severe energy constraints….”
- “Independent of phylogenetic origin, almost all animals have evolved strategies using sensory modalities and motor plants to support gaze stabilization.”
- “The combination of feedforward and feedback signals in control architectures has also evolved in other gaze stabilization systems.”
- “Aspects of behavior, including species-specific locomotor modes, the use of sensory systems and of motor systems — all of which are likely to have evolved in parallel — therefore need to be considered as reasons for the origin of a given gaze control strategy.”
- “Different phyla have evolved diverse motor systems for gaze stabilization, which nevertheless exhibit similarities in design.”
- “In most cases, they have evolved a rather sophisticated neck motor system to do so.”
- “Adaptations to these interactions include the specification of sensory modalities and motor systems, which have likely evolved in parallel to simplify the integration of sensory signals and their transformation into motor commands for controlling behavior.”
Why, you ask, have they evolved? Because image stabilization systems are good designs. They help the animals. Indeed, their first sentence agrees, “The use of vision to coordinate behavior requires an efficient control design that stabilizes the world on the retina or directs the gaze towards salient features in the surroundings.”
When have they evolved? “A visual streak that is stabilized to align with the external horizon evolved in ancient crustaceans, for instance, which first appeared during the Cambrian explosion about 511 million years ago,” they confidently state. Crustaceans, we note, have eyes, limbs, guts, muscles, sexual organs, and much more. Presumably all those things “have evolved,” along with the brains that exploded onto the scene with everything else.
Since everything evolves, understanding must evolve, too. That’s what Niven and Chittka say in their Guest Editorial in Current Biology, “Evolving understanding of nervous system evolution.” Are we there yet? Do we understand? We’ll let them describe the problem Darwinians face:
Nervous systems encompass a staggering diversity from nerve nets of just a few hundred neurons — as in the nematode worm Caenorhabditis elegans — to the highly centralised and cephalised nervous systems of arthropods that may contain a million neurons, as in the honeybee, and those of cephalopod molluscs, such as the octopus, and amniotes that can contain hundreds of millions to billions in the case of the human brain. Nervous systems have been evolving in concert with the animals that possess them since the Precambrian more than 580 million years ago. Arguably, all extant nervous systems are success stories; no single one is inherently better than any other: they are the products of different sets of evolutionary pressures produced by different life histories. Our knowledge of nervous systems is derived from multiple levels and types of analysis: genetics, development, cell signalling, morphology, biophysics, physiology and behaviour. Understanding how so many organisational levels are integrated to produce even a single behaviour is difficult; understanding their evolution even more so.
Understanding takes hard work. It’s much easier just to stipulate what you want to believe. As they bluntly assert at one point, “Brains are not designed but evolve ‘blindly’ through selection.”
If you’ve got a headache by now, relax and consider that the failure of these articles to address Meyer’s critique of Darwinian explanations for the Cambrian explosion constitutes strong affirmation that his critique is sound. If they had better evidence and arguments, they surely would provide them.
Source: On the Origin of Brains