 A report published in the "American Journal of Physical Anthropology" in January 2015 reviewed craniofacial variation focussing on differences between early and late Native Americans and explanations for these based on either skull morphology or molecular genetics.Arguments based on molecular genetics have in the main, according to the authors, accepted a single migration from Asia with a probable pause in Berengia, plus later bi-directional gene flow.Studies focusing on craniofacial morphology have argued that Paleoamerican remains have "been described as much closer to African and Australo-Melanesians populations than to the modern series of Native Americans", suggesting two entries into the Americas, an early one occurring before a distinctive East Asian morphology developed (referred to in the paper as the "Two Components Model".