Posted: Jul 15, 2017 10:49 pm
On a more detailed note, looking at the phylogeny of primates, we share a Catarrhine common ancestor with the SuperFamily Cercopithecidoidea, the Old World Monkeys, but you have to go back further, to the divergence of the Simiiformes, to find a shared ancestor with the New World Monkeys, that belong to the ParvOrder Platyrrhini. At this point, the classification scheme reflects the disparity between lay understanding of these organisms, and a rigorous phylogenetic view.
The ParvOrder Playtrrhini, considered in isolation, is a monophyletic clade - it contains all of the descendants of a specific ancestor. Likewise, so does the SuperFamily Cercopithecoidea. Trouble is, treating both of these groups as comprising "monkeys", results in a paraphyletic assemblage: the resulting assemblage does NOT contain all descendants from the relevant Simiiform ancestor, as that ancestor also gave rise, via the Catarrhini, to another branch of the tree, the Hominoidea. The term "monkey", as applied popularly, does not dovetail with the known phylogeny of the requisite organisms, and thus its use in any proper scientific discussion of our ancestry is invalid.
It's at this point, that the real nature of the question moves from the simplistic, misleading, and phylogenetically invalid "are we monkeys?", to "what is the phylogenetic status of our common ancestor with the Cercopithecoidea?", a question that is both more rigorous and more illuminating. The answer to that latter question, of course, being that said ancestor was a Catarrhine primate, and consequently, so are we. As indeed, we are members of every clade that gave rise to the Catarrhines, including the Simiiformes, right the way down to the Chordata, the Deuterostomata, the Bilateria and the Eumetazoa.
The ParvOrder Playtrrhini, considered in isolation, is a monophyletic clade - it contains all of the descendants of a specific ancestor. Likewise, so does the SuperFamily Cercopithecoidea. Trouble is, treating both of these groups as comprising "monkeys", results in a paraphyletic assemblage: the resulting assemblage does NOT contain all descendants from the relevant Simiiform ancestor, as that ancestor also gave rise, via the Catarrhini, to another branch of the tree, the Hominoidea. The term "monkey", as applied popularly, does not dovetail with the known phylogeny of the requisite organisms, and thus its use in any proper scientific discussion of our ancestry is invalid.
It's at this point, that the real nature of the question moves from the simplistic, misleading, and phylogenetically invalid "are we monkeys?", to "what is the phylogenetic status of our common ancestor with the Cercopithecoidea?", a question that is both more rigorous and more illuminating. The answer to that latter question, of course, being that said ancestor was a Catarrhine primate, and consequently, so are we. As indeed, we are members of every clade that gave rise to the Catarrhines, including the Simiiformes, right the way down to the Chordata, the Deuterostomata, the Bilateria and the Eumetazoa.