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Scaffold Without a Blueprint? Another Wild Story of Cambrian “Enablement”


For a billion years, microbes were lonely. They swam as individuals, occasionally forming little clubs to pass the millions of years together. Then, one of them found a Lego-like protein in its cytoplasm. Poking it outside its cell membrane, the curious fellow kept doing this, till some of the useless castoffs formed networks of strands floating in the water. As the microbe divided, its offspring latched onto the meshwork.

Bang! Animals!

We hope that is not too silly a retelling of the latest evolutionary attempt to explain away the Cambrian explosion. David McNamee of Vanderbilt puts it this way, via Science Daily:

The dawn of the Animal Kingdom began with a collagen scaffold that enabled the organization of cells into tissues.

This key innovation, which made possible the rich diversity of life on earth, is found in the most ancient of currently living animals — the ctenophore, Vanderbilt University Medical Center scientists report in the online journal eLife. [Emphasis added.]

Well, if a collagen scaffold “enabled” tissues, what microbe wouldn’t want to take advantage of the free offer? Did the microbe recognize what a “key innovation” collagen was? Did it know what to do with a scaffold? Did it imagine the possibilities? Someone should remind the thinkers in the evolutionary community that possibility is not evidence.

Oh, but animals have tissues made with collagen! So there you go. Evidence! It’s perplexing that McNamee and his scientific colleagues look to ctenophores (comb jellies) to support their story. Comb jellies recently occasioned howls of protest when Antonis Rokas, one of the co-authors of the eLife paper, contended that they — not sponges — were the first animals. Another Vanderbilt news item explains:

For nearly a century, scientists organized the animal family tree based in large part on their judgement of the relative complexity of various organisms. Because of their comparative simplicity, sponges were considered to be the earliest members of the animal lineage. This paradigm began to shift when the revolution in genomics began providing vast quantities of information about the DNA of an increasing number of species. Evolutionary biologists started to apply this wealth of information to refine and redefine evolutionary relationships, creating a new field called phylogenomics. In most cases, the DNA data helped clarify these relationships. In a number of instances, however, it gave rise to controversies that intensified as more and more data accumulated.

Since then, evolutionists have batted the shuttlecock of earliest animal back and forth between the sponge-firsters and the ctenophore-firsters. What matters here is that Rokas is a ctenophore-firster. And yet now his institution is claiming that this complex animal, the comb jelly, with its symmetry, flashing lights, nervous system, gut, and complex behaviors, is the heir of a blind, aimless collagen scaffold. Some steps seem to be missing in this story. (And remember, ctenophores are just one of the 18 to 20 phyla that appear abruptly in the Cambrian.)

The open-access paper in eLife relies on the concept of “enablement.” If collagen emerges, it will “enable” complex life to emerge.

The role of the cellular microenvironment in enabling metazoan tissue genesis remains obscure. Ctenophora has recently emerged as one of the earliest-branching extant animal phyla, providing a unique opportunity to explore the evolutionary role of the cellular microenvironment in tissue genesis. Here, we characterized the extracellular matrix (ECM), with a focus on collagen IV and its variant, spongin short-chain collagens, of non-bilaterian animal phyla. We identified basement membrane (BM) and collagen IV in Ctenophora, and show that the structural and genomic features of collagen IV are homologous to those of non-bilaterian animal phyla and Bilateria. Yet, ctenophore features are more diverse and distinct, expressing up to twenty genes compared to six in vertebrates. Moreover, collagen IV is absent in unicellular sister-groups. Collectively, we conclude that collagen IV and its variant, spongin, are primordial components of the extracellular microenvironment, and as a component of BM, collagen IV enabled the assembly of a fundamental architectural unit for multicellular tissue genesis.

Microbes don’t have collagen; ctenophores do have it (20 genes of it), therefore the mere appearance of collagen must have “enabled” a microbe to perform “tissue genesis.” Presto! Comb jellies. Watch these little guys on YouTube strut their fancy lights.

We’ll rank this explanation a little higher than the idea that oxygen enabled the Cambrian body plans. But not by much. You can find the word “enabled” a dozen times in the paper, e.g.:

Knowledge of collagen IV evolution may shed light on the fundamental features of the cellular microenvironment that enabled the transition from single-cell organisms to multicellular tissues. Together, the non-bilaterian animal phyla (Ctenophora, Porifera, Placozoa, and Cnidaria) represent this transition [i.e., the Cambrian explosion]. Importantly, Ctenophora has recently emerged as one of the earliest-branching extant phyla….

Questioning the Explosion

While on the topic of the Cambrian explosion, let’s look briefly at a new paper in Geology that questions the explosiveness of the radiation. Five scientists went to an outcrop in Siberia where the transition from Ediacaran to Cambrian is exposed. By measuring carbon isotopes, fossils, small shellies and burrows, they conclude that the Cambrian explosion had “deep roots.”

These observations raise doubts as to whether there is any true separation between the Ediacaran and Cambrian skeletal biotas, and suggest that there is a deep root for the Cambrian explosion of metazoans.

While interesting, the outcrop is irrelevant to the central thesis of Stephen Meyer’s book, Darwin’s Doubt. Meyer claims that the abrupt appearance of new body plans in the early Cambrian requires a cause able to organize hierarchical layers of information into functional structures. The only cause we know that can do that is intelligence. With that in mind, it doesn’t matter how much time you give them; blind processes of evolution can’t do it.

This new paper adds little to the discussion. Paleontologists already knew about small shelly fossils, Ediacaran organisms, and debates about deep roots. Basically, the geologists and paleontologists found overlap between the Ediacaran, the small shelly fossils and the Cambrian animals in this Siberian outcrop. “These observations in turn raise doubts as to whether there is any true separation between the Ediacaran and Cambrian skeletal biotas,” they conclude. That’s all well and good, but it’s not the issue. Where did the information for complex body plans come from? Notice what’s missing from this paper:

  • Evolution: They don’t even mention it.
  • Genetics: They don’t mention that, either.
  • Ancestry or phylogeny: Zero mentions.

Instead, they simply say, “In conclusion, our new integrated data do not support the contention that extinction of the Ediacaran biota facilitated the Cambrian explosion, but rather suggest that there is a deep root for the Cambrian explosion of metazoans.”

They don’t deny the explosion, in other words. They just find overlap between the Ediacarans (which are not related to the Cambrian animals), the small shellies and burrows, and the fully formed Cambrian body plans.

That word “facilitated” is noteworthy. It’s like the word “enabled” in the previous paper. You can “enable” a building all you want by erecting scaffolds. You can “facilitate” the building by getting trash out of the way. But without intelligence, nothing will happen.

By the way, do take a moment to view the earliest Cambrian arthropod, estimated to be 508 million years old, just discovered in Canada, over at Live Science. This “sea monster” had fifty legs and giant claws — some of the strongest claws on record. It also had shells, eyes, and antennae. “The new finding is only the latest fossil discovery from Marble Canyon. Other Cambrian fossil discoveries there include an ancient fish known as Metaspriggina and a four-eyed arthropod called Leanchoilid.”

That’s the kind of architecture that evolutionists have yet to explain.

Photo: Arctic comb jelly (Mertensia ovum), by Kevin Raskoff (Mertensia on oceanexplorer.noaa.gov) [Public domain], via Wikimedia Commons.