A giant barrel sponge from Indonesia. Sponges were the first reef builders and maintain a fundamental role in modern marine ecosystems.
Creationists have a massive gap to try to close; a gap so wide it makes the Grand Canyon look like a mere ditch. It is the gap between the earliest signs of life in the fossil record and the timeline a literal reading of the Bible allows. And that gap just got a lot wider.
Creationists could once take comfort from the fact that there was little solid fossil evidence of multicellular life much before the Cambrian, when organisms with hard body parts that fossilise begin to appear in the record. That gap was closed, not by fossils as we normally understand the term, but by chemical fossils contained in ancient rocks, as I explained in my last blog post. This evidence, together with genetic evidence from other work, shows that the common ancestors of multicellular animal life were very probably sea sponges.
But to a creationist, conditioned to believe that the Theory of Evolution is a theory about fossils—so that any gaps in the fossil record must be fatal for the theory—there is still some comfort in the fact that whatever left these chemical fingerprints in ancient rocks left no tangible fossils.
Now a team of palaeontologists, led by the University of Bristol, have shown that the lack of fossil evidence of these ancestral sponges has a simple explanation: they were soft-bodied, having yet to evolve the characteristic skeletons composed of millions of microscopic glass-like spicules. These did not evolve until about 560 million years ago. The team have recently published their findings, open access, in the journal Science Advances.
The Bristol-led team have now pushed back the evolution of these soft-bodied sponges to between 615 and 600 million years ago by using a combination of genetic evidence from 133 protein-coding genes and fossil evidence. This approach also showed that the spicules evolved independently in different sponge groups by convergent evolution.


































