This is a totally astonishing experiment:
The exact moment when a 550 million year old cell began to divide has been captured in an exquisite 3-D image.
The picture is one of a series taken by researchers examining ancient fossil embryos from Guizhou Province, China.
The specimens, described in the journal Science, are the oldest known examples of fossil embryos, and shed light on the early evolution of complex life.
Scientists used an advanced X-ray technique to peer inside the balls of cells to reveal the structures inside.
If it didn't sink in, read that again: scientists have managed to peer inside fossilised embryos that are 550 million years old. That's pre-Cambrian to those who understand that sort of thing (and pre-pre-pre-dinosaurs to those who don't). Doesn't modern technology just blow you away?
More importantly, the experiment opens up a new line of enquiry into the Cambrian Explosion debate:
…Using the microCT technique to analyse late stage embryos, with up to 1,000 cells, the team was able to gain insights into the creature that produced them.
…The team believes the cells probably came from extremely simple creatures.
"They would have developed into sponge-like creatures, but more primitive," said Dr. Donoghue [of the University of Bristol in the UK].
If right, this means that the Cambrian Explosion theory for the origin of complex animal life would still stand
"This work provides a constraint on when advanced groups evolved," Dr Donoghue said.
I'm not sure if I understand this last point: just because these particular fossils are primitive, why does that put any limit on when advanced groups evolved? Why couldn't primitive and advanced species have lived at the same time? (I hate the words primitive and advanced, by the way; simple and complex seem far more appropriate.)