UC Santa Barbara neuroscientist Kenneth S. Kosik, whose focus is the evolution of the brain, reports at Nautilus that he and colleagues have observed a striking fact: The sea sponge, which dates back to 600 million years ago, has no neurons and no brain. Yet its 18 different cell types have many of the genes required for a brain.

“Ever since,” he admits, “we have asked ourselves why this ancient, porous blob of cells would contain a set of neural genes in the absence of a nervous system? What was evolution up to?”

A brain assembly kit

The sponge, an immobile, passive bottom feeder, is a multicellular animal, thus much more complex than the single-celled life forms that preceded it for three billion years. But what about the brain assembly kit that is present without a brain?

Kosik considers two types of very early multicellular animals, sponges and comb jellies. Comb jellies, which do have a nervous system, deepen the mystery in his view: “Did the common ancestor of both the sponge and comb jelly already have a nervous system that was lost in the sponge? Or did the nervous system get invented twice, once in the comb jelly and then again in the evolutionary descendants of the sponge?”

Kosik thinks one clue might lie in the synapse, the part of a neuron that enables it to communicate with another cell. Perhaps, after the journey to a nervous system began in the original single-celled organisms, the sponge repurposed its synapses for another use and the comb jelly did not. If so, that earliest nervous system seems lost to follow-up.

The mystery of evolvability

Kosik ends his essay with this reflection:

How astounding that within a 600-million-year-old sea sponge, a gene set lay the framework for a future that could not have been anything more than an abstract space, an intangible dream, as elusive as the space of consciousness.

This abstract space is the property of “evolvability,” built deeply within the structure of biology, to create variation among species that is heritable and increases the organism’s fitness for its environment. Evolvability does not reside in any gene sequence but is a collective property through which genes are connected to the environment.

The sea sponge, with its unrealized nervous system, was oblivious to the eons that stretched out in front of it, as it silently worked out its future. That future lay in its genes, a set of instructions that can faithfully reproduce over generations and change form as they evolve. Evolution conferred the unassuming sea sponge with a genetic program that made possible the vast variety of future lifeforms. Together life intricately and beautifully melds constancy over generations and change over evolutionary time in a beautiful dance.

Kenneth S. Kosik, “Where Did the Brain Come From?,” Nautilus, September 12, 2023

Notice what the concept of evolution has become here. “Evolvability” is not really a Darwinian mechanism like “survival of the fittest.” Rather, it is an abstraction like “capability.” It is the “ability” to evolve. But no ability comes from nothing. What is the ability’s origin?

In the brainless sponge, we are looking at a toolkit for a nervous system whose origin is unknown. To the extent that the later evolution of a nervous system in the sponge’s assumed descendants depends on that toolkit, it depends on a mystery. And that mystery does not invite a Darwinian explanation; rather, when a Darwinian explanation is demanded, that is likely to be for ideological reasons.

Evolution as an engineer

Not only does the toolkit not demand a Darwinian explanation, Kosik’s description of evolvability is nearly anthropomorphic. Evolution, as he describes it, works like an engineer on its designs: “Evolution conferred the unassuming sea sponge with a genetic program that made possible the vast variety of future lifeforms.”

And yet we are also asked by the gatekeepers of science to believe that evolution does not and cannot have foreknowledge of any kind because the universe we live in is without purpose or design. Even our own designing minds are an illusion.

Kosik may very well say that he is merely using poetic imagery when he describes evolution in this way. The trouble is, when the imagery so naturally drifts to design rather than Darwinism, the reason may not be the limits of language. What looks like purpose may not be illusory. What looks like design may be real.

Of course, if a theorist cannot address purpose or design, there is a convenient escape: The correct design-free explanation has surely been lost, along with the unpreserved unicellular life forms in which the proto-nervous system originated. Practically anything can get lost that way.

Further discussion depends on whether we find more toolkits in other genomes. At least we know about it and are talking about it now.

You may also wish to read: Did minimal consciousness drive the Cambrian Explosion? Eva Jablonka’s team makes the daring case, repurposing Hungarian chemist Tibor Gánti’s origin of life studies. The researchers point out that life forms that show minimal consciousness have very different brains. Behavior, not brain anatomy, is the signal to look for.