However, free interbreeding between A. cujubi and A. cumanensis grayi in eastern Bolivia, creating a "hybrid swarm", casts doubt on this conclusion for the two species named.

The white-faced lineage emerged around 3 mya and its present diversity began to evolve around the Pliocene-Pleistocene boundary, when the ancestors of the red-throated piping guan and the blue-wattled taxa split.

However, although the relationships of the genera of guans are not entirely clear, it seems most likely that the group originated in the northern Andes region: The northernmost guan genera Chamaepetes and Penelopina appear to be basal divergences, and Pipile is most likely closer to Penelope (which represents a generally southward radiation out of the northern Andes) than to these.

Thus it appears most likely that the present genus diverged in the eastern foothills of the Andes somewhere in the vicinity of Bolivia, far to the northwest from where its origin would be presumed from the phylogeny and present-day distribution of Pipile alone.

[5] Secondly, it is notable that in the Late Pliocene, rising sea levels transformed much of the South American lowlands into brackish lagoon habitat unsuitable for piping guans.