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Archaeological and isotopic evidence from Greater Cahokia and several prominent outlier sites argues against simple diaspora models either for the rise or fall of this pre-Columbian urban phenomenon. Besides indications that a culturally diverse population was associated with the city throughout its history, we argue that a spiritual vitality undergirded its origins such that many movements of people would have been two-way affairs. Some Cahokians who ultimately left the city may have been members of foreign lineages in the beginning.

Analyses of house-size distributions in the Old and New World showed that wealth disparities increased with the domestication of plants and animals and with increased sociopolitical scale. Beneath headlines about booms and busts and other economic disturbance lies a deeper problem: wealth inequality. But what is its history, and what are the larger social factors that determine the disparate distribution of wealth? Timothy Kohler and colleagues look at the evolution of inequality worldwide since the Neolithic era, around 11,000 years ago, using house size as a proxy for calculating the Gini coefficient, a measure of wealth inequality. The study shows that, as may be expected, wealth inequality has generally increased. Unexpectedly however, inequality increased far more in the Old World of Europe and Asia than in the New (North and Central America). Even in highly urban New World sites, house sizes are generally similar. There are no enormous palaces, which one expects in Old World urban contexts. The authors suggest that the inherent wealth provided by large domesticated animals could explain the imbalance. Horses, for example, allowed people to ride around acquiring wealth from others. How wealth is distributed among households provides insight into the fundamental characters of societies and the opportunities they afford for social mobility1,2. However, economic inequality has been hard to study in ancient societies for which we do not have written records3,4, which adds to the challenge of placing current wealth disparities into a long-term perspective. Although various archaeological proxies for wealth, such as burial goods5,6 or exotic or expensive-to-manufacture goods in household assemblages7, have been proposed, the first is not clearly connected with households, and the second is confounded by abandonment mode and other factors. As a result, numerous questions remain concerning the growth of wealth disparities, including their connection to the development of domesticated plants and animals and to increases in sociopolitical scale8. Here we show that wealth disparities generally increased with the domestication of plants and animals and with increased sociopolitical scale, using Gini coefficients computed over the single consistent proxy of house-size distributions. However, unexpected differences in the responses of societies to these factors in North America and Mesoamerica, and in Eurasia, became evident after the end of the Neolithic period. We argue that the generally higher wealth disparities identified in post-Neolithic Eurasia were initially due to the greater availability of large mammals that could be domesticated, because they allowed more profitable agricultural extensification9, and also eventually led to the development of a mounted warrior elite able to expand polities (political units that cohere via identity, ability to mobilize resources, or governance) to sizes that were not possible in North America and Mesoamerica before the arrival of Europeans10,11. We anticipate that this analysis will stimulate other work to enlarge this sample to include societies in South America, Africa, South Asia and Oceania that were under-sampled or not included in this study.

The combined movements of local and foreign people from pre-Mississippian villages and hamlets into mound centers and out to isolated farmsteads resulted in the creation of Cahokia at AD 1050 as an urban space and the center of a regionally integrated polity. Through these movements, landscapes were redefined and identities and power relations among local and foreign groups were negotiated. It is asserted that such movements interfered with local sources of power while a sense of shared identity was fostered through participation in communal events. Through analyses of site layout, occupational history, and material culture, the historical effects of these movements are traced.

Nature 551, 619–622 (2017); doi:10.1038/nature24646 In this Letter, the following paragraph was inadvertently omitted from the Methods section: ‘Gini coefficients for Tikal (Classic Maya) and Kahun (Middle Kingdom Egypt) were calculated from data compiled from site maps by the project ‘Service Access in Premodern Cities’ (http://cities.wikispaces.asu.edu/).