News Finding: They found that when some early branches of the arthropod family tree were splitting off, creatures were evolving new traits about four times faster than they did in the following 500 million years.
Paper Finding: The elevated Cambrian rates of phenotypic evolution are unlikely to be an artifact of oversampling of characters changing on early arthropod branches, for two reasons.
News Context: For any two branches of the arthropod family tree--centipedes and millipedes, for example--they picked out important physical differences and variations in genetic sequence in modern specimens. They found that when some early branches of the arthropod family tree were splitting off, creatures were evolving new traits about four times faster than they did in the following 500 million years. The creatures' genetic codes were changing by about .117% every million years--approximately 5.5 times faster than modern estimates, the group reports online today in Current Biology.
Paper Context: Such scenarios do not predict that genes involved in basic metabolic and cellular processes common to all panarthropods should have faster evolutionary rates in earlier panarthropod lineages. The elevated Cambrian rates of phenotypic evolution are unlikely to be an artifact of oversampling of characters changing on early arthropod branches, for two reasons. Second, the molecular data exhibit an almost identical Cambrian rate burst yet cannot suffer such ascertainment bias (because gene sequencing samples every single nucleotide in a gene region, not just sites changing on particular branches).