In cladistics, an outgroup's a (monophyletic) group of organisms that serves as a reference group for determination of the evolutionary relationship between three or more monophyletic groups of organisms. The choosen outgroup's hypothesized to be rather closely related to the other groups, but less closely than any single one of the other groups's to each other. The evolutionary conclusion from this's that the outgroup branched from the parent group before the other two groups branched from each… (More on Outgroup)