 Their concern is that the proximate-ultimate distinction has discouraged consideration of the manner in which developmental processes can set the evolutionary agenda, for instance, by introducing innovations, channeling phenotypic variation, or initiating evolutionary episodes through modifying selection pressures.One the other side are researchers who largely adopt Mayr's stance with a clean separation of proximate and ultimate causation.For the latter, a failure to respect Mayr's dichotomy is considered a sign of confusing an evolutionary explanation with a mechanistic explanation.