Rui Diogo, Luke J Matthews and Bernard Wood
Molecules are rapidly replacing morphology as the preferred source of evidence for generating phylogenetic hypotheses. Critics of morphology claim that most morphology-based characters are ambiguous, subjective and prone to homoplasy. In this paper we summarize the results of recent Bayesian and parsimony-based cladistic analyses of the gross muscle morphology of primates and of other animals that show that morphological evidence such as muscle-based data is as capable of recovering phylogenies as are molecular data. We also suggest that recent investigations of neural crest cells and muscle connectivity might help to explain why muscles provide particularly useful characters for inferring phylogenies. Lastly, we show how the inclusion of soft tissue-based information in phylogenetic investigations allows researchers to address evolutionary questions that are not tractable using molecular evidence alone, including questions about the evolution of our closest living relatives and of our own clade.