News Finding: Lee calls this pace "fast, but not too fast" to reconcile with Darwin's theory.
Paper Finding: Thus, the assumption of rate constancy through time means that extensive morphological and molecular divergences between the primary arthropod groups must be accommodated on chronologically long branches, leading to very early basal divergences inconsistent with the fossil record.
News Context: 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. Lee calls this pace "fast, but not too fast" to reconcile with Darwin's theory. This combined model for genes and anatomy represents "quite a stride forward," Wills says.
Paper Context: The present study reveals that in order to equalize morphological and molecular evolutionary rates before and after the Cambrian explosion, the root of panarthropods needs to be w940 Myr old (Table S3 : soft-bounded root). Thus, the assumption of rate constancy through time means that extensive morphological and molecular divergences between the primary arthropod groups must be accommodated on chronologically long branches, leading to very early basal divergences inconsistent with the fossil record. The present study reveals that constraining root age to any figure even loosely consistent with the fossil record (e.g., <650 Ma) implies elevated rates of morphological and molecular evolution in the late Precambrian.