MrDarwin

<a href="http://www.sciencedaily.com/releases/2002/09/020927064725.htm" target="_blank">Study Suggests Macroscopic Bilaterian Animals Did Not Appear Until 555 Million Years Ago</a>

<a href="http://www.info.ucr.edu/cgi-bin/display.cgi?id=276" target="_blank">University of California, Riverside study dates our ancestors</a>

pz

I'm afraid I don't find this very credible -- it's relying on the absence of evidence (a very specific form of evidence, trace fossils) to draw a conclusion. It's interesting that they find an increase in complexity of trace fossils at a time shortly before the Cambrian, but that doesn't mean the Bilateria didn't evolve until that moment.

It would have been much more appropriate for them to say that they've found evidence of increasing metazoan complexity at least 10 million years before the start of the Cambrian. That's a defensible and interesting claim.