Helicolocellus cantori in an Ediacaran sea
AI-generated image (ChatGPT Latest)
Scientists have narrowed another gap in the fossil record and, as usual, no gods were found. The gap concerned the long interval between the time molecular-clock analyses suggest sponges first evolved in the Neoproterozoic, perhaps around 700 million years ago, and the earliest widely accepted sponge fossils from the early Cambrian. That gap has now been pushed back into the Late Ediacaran by Virginia Tech geobiologist a paper in Nature.
Creationists normally delight in gaps in the fossil record because they think Darwin somehow “admitted” that missing links were fatal to his theory. In reality, Darwin was doing what honest scientists do: openly acknowledging the limitations of the evidence available in 1859. The key point is that he was writing about the state of knowledge then, not in 2026. Since Darwin’s day, the Theory of Evolution has not only provided a framework for understanding the history of life; it has also told scientists what sort of evidence to look for and where to look for it. As a result, palaeontologists now have access to vastly more fossils than Darwin could ever have imagined, together with genetic evidence and radiometric dating methods that did not exist in his lifetime. More fossils are being found almost daily and invariably confirm the Theory of Evolution.
And those gaps continue to shrink, almost always to the discomfort of creationists, because they so often concern events hundreds of millions, even billions, of years before the narrow timescale allowed by biblical literalism. This fossil is especially awkward for them because it further undermines the familiar creationist misrepresentation of the Cambrian “Explosion” as a sudden, magical appearance of multiple body plans with no ancestry. Instead, this Late Ediacaran sponge adds to the growing evidence that the Cambrian diversification was preceded by a long evolutionary prelude, in which animals were already emerging and diversifying before the Cambrian began. Far from an abrupt act of creation, the picture is one of gradual evolutionary change over immense spans of time, as the largely sessile Ediacaran world gave way to the more active and ecologically complex Cambrian one.
The Evolution of Sponges.The discovery and its significance are explained in a Virginia Tech news item by Kelly Izlar.
- Sponges (Porifera) are among the earliest-diverging animal lineages. They are simple, sessile filter-feeders with bodies built around pores, canals and choanocyte (“collar”) cells that pump water through the body. They have no nervous system, no gut and no true organs. [1.1]
- They are simple, but not “primitive failures”. Their body plan is highly effective for suspension feeding and has remained successful for hundreds of millions of years in marine and freshwater habitats worldwide. [1.1]
- Sponges are important because they illuminate the origin of animals. Genetic studies show that many of the molecular systems later used in more complex animals for cell adhesion, signalling and development were already present very early in animal evolution. [2.1]
- For years there was a mismatch between genes and fossils. Molecular-clock studies and related evidence suggested sponges evolved well before the Cambrian, but convincing sponge fossils were mostly known from about 540 million years ago, leaving a long gap in the record. [3.1]
- The likely reason is that the earliest sponges were soft-bodied. Without hard mineralised spicules or rigid skeletons, early sponges would have been much less likely to fossilise, so their early history was largely hidden. [4.1]
- Recent work is narrowing that gap. The Late Ediacaran fossil Helicolocellus cantori, from about 551–539 million years ago, appears to be a crown-group sponge and suggests that early sponges existed before the Cambrian even if they lacked the hard skeletons seen in many later forms. [1.13
- The broader picture is now much clearer. Sponges did not suddenly appear in the Cambrian; they were part of a longer pre-Cambrian evolutionary history, showing that the Cambrian diversification had deep roots rather than being a sudden, unexplained event. [4.1]
Virginia Tech researcher's team discovers 'missing' sea sponges
The discovery, published in the journal Nature, opens a new window on early animal evolution.
At first glance, the simple sea sponge is no creature of mystery.
No brain. No gut. No problem dating it back 700 million years. Yet convincing sponge fossils only go back about 540 million years, leaving a 160 million-year gap in the fossil record.
In a paper released June 5 in the journal Nature, Virginia Tech geobiologist Shuhai Xiao and collaborators reported a 550 million-year-old sea sponge from the “lost years” and proposed that the earliest sea sponges had not yet developed mineral skeletons, offering new parameters to the search for the missing fossils.
The mystery of the missing sea sponges centered on a paradox.
Molecular clock estimates, which involve measuring the number of genetic mutations that accumulate over time, indicate that sponges must have evolved about 700 million years ago. And yet there had been no convincing sponge fossils found in rocks that old.
For years, this conundrum was the subject of debate among zoologists and paleontologists.
This latest discovery fills in the evolutionary family tree of one of the earliest animals, explaining its apparent absence in older rocks and connecting the dots back to Darwin’s questions about when it evolved.
Xiao, who recently was inducted into the National Academy of Sciences, first laid eyes on the fossil five years ago, when a collaborator texted him a picture of a specimen excavated along the Yangtze River in China.
I had never seen anything like it before. Almost immediately, I realized that it was something new.
Shuhai Xiao, co-corresponding author.
Department of Geosciences and Global Change Centre
Virginia Tech
Blacksburg, VA, USA.
Xiao and collaborators from the University of Cambridge and the Nanjing Institute of Geology and Paleontology began ruling out possibilities one by one: not a sea squirt, not a sea anemone, not a coral. They wondered, could it be an elusive ancient sea sponge?
In an earlier study published in 2019, Xiao and his team suggested that early sponges left no fossils because they had not evolved the ability to generate the hard needle-like structures, known as spicules, that characterize sea sponges today.
Xiao’s team members traced sponge evolution through the fossil record. As they went further back in time, sponge spicules were increasingly more organic in composition and less mineralized.
If you extrapolate back, then perhaps the first ones were soft-bodied creatures with entirely organic skeletons and no minerals at all. If this was true, they wouldn’t survive fossilization except under very special circumstances where rapid fossilization outcompeted degradation.
Shuhai Xiao.
Later in 2019, Xiao’s international research group found a sponge fossil preserved in just such a circumstance: a thin bed of marine carbonate rocks known to preserve abundant soft-bodied animals, including some of the earliest mobile animals.
Most often, this type of fossil would be lost to the fossil record. The new finding offers a window into early animals before they developed hard parts..
Shuhai Xiao.
The surface of the new sponge fossil is studded with an intricate array of regular boxes, each divided into smaller, identical boxes.
This specific pattern suggests our fossilized sea sponge is most closely related to a certain species of glass sponge.
Dr. Xiaopeng Wang, first-author
State Key Laboratory of Palaeobiology and Stratigraphy
Nanjing Institute of Geology and Palaeontology
Chinese Academy of Sciences
Nanjing, China.
Another unexpected aspect of the new sponge fossil is its size.
When searching for fossils of early sponges I had expected them to be very small. The new fossil is about 15 inches long with a relatively complex, conical body plan, which challenged many of our expectations for the appearance of early sponges.
Alexander G. Liu, co-author
Department of Earth Sciences
University of Cambridge
Cambridge, UK.
While the fossil fills in some of the missing years, it also provides researchers with important guidance about how to search for these fossils — which will hopefully extend understanding of early animal evolution further back in time.
The discovery indicates that perhaps the first sponges were spongey but not glassy. We now know that we need to broaden our view when looking for early sponges.
Shuhai Xiao.
Publication:Wang, X., Liu, A.G., Chen, Z. et al.
A late-Ediacaran crown-group sponge animal.
Nature 630, 905–911 (2024). https://doi.org/10.1038/s41586-024-07520-y
What finds like this do, yet again, is expose the intellectual bankruptcy of creationism’s dependence on gaps in the evidence. Every time one of those gaps is narrowed or closed, the creationist position is not strengthened but weakened, because its case so often rests not on positive evidence but on the hope that science has not yet found something. That is a fragile strategy when science is a cumulative, self-correcting process that keeps adding new data, refining old ideas, and bringing ever more of life’s history into focus.
This Late Ediacaran sponge is especially damaging to the familiar creationist caricature of the Cambrian “Explosion” as a moment of sudden, inexplicable creation. What the evidence increasingly shows instead is a long prelude: lineages already existed, body plans were already beginning to emerge, and the Cambrian diversification was built on foundations laid millions of years earlier. In other words, the “explosion” was not magic; it was evolution working over deep time.
And deep time is, of course, the real problem here for biblical literalism. Fossils such as these come from a world more than half a billion years old, embedded in geological contexts that cannot be compressed into a 6,000–10,000-year timetable without discarding virtually everything modern geology, palaeontology, physics and geochemistry have discovered. The more we learn about the Ediacaran and Cambrian worlds, the clearer it becomes that Earth’s history is unimaginably older, richer and more complex than the authors of Bronze Age mythology could ever have known.
So, once again, the verdict of the rocks is unequivocal. Life did not appear all at once in its modern forms; it has a deep history, marked by gradual change, branching descent, extinction and innovation across immense spans of time. Each new fossil discovery adds another piece to that picture, and each new piece makes the creationist story look less like an alternative explanation and more like what it has always been: a pre-scientific myth unable to survive contact with the evidence.
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