Bradley T. Lepper commentary: Climate had role in changing cultures

American Indian cultures in ancient Ohio changed over time. The earliest Ice Age colonists are known as Paleoindians. By 10,000 years ago, the Ice Age had come to an end and the Archaic cultures developed over the next 6,000 years.

The domestication of local plants initiated the transformation of Archaic to the succeeding Woodland cultures. Over time, cultural complexity increased, culminating in the rise of the Late Prehistoric cultures by about 1,000 years ago.

Understanding why cultures changed is one of the most fascinating problems in archaeology. Significant cultural transformations have been attributed to various factors such as technological evolution, migrations of people or climate change.

In recent years, however, researchers have tended to dismiss the role of climate change as a kind of "environmental determinism" that some felt diminished the role of human initiative in shaping our various cultures.

A review of the latest paleoenvironmental and archaeological data now firmly establishes the importance of climate change for understanding the reasons cultures change.

University of Ottawa paleoclimatologist Samuel Munoz and colleagues, writing in the Proceedings of the National Academy of Sciences, demonstrate that nearly every cultural transition in the northeastern United States corresponds with a major transition in the climate of the region.

The change from the Paleoindian to the Early Archaic cultures, for example, corresponds to "a shift toward a drier and warmer climate," they wrote. The change from the Archaic to the Woodland cultures corresponds to a period of gradual cooling.

Of course, not every cultural change is a direct response to climate change.

Bits of charcoal become more common in sediment dating to the Early Woodland, which Munoz and his co-authors suggest is because humans set more fires. Burning is one way indigenous peoples manage the landscape.

Early Woodland folks in Ohio might have used burning to open up land for gardens, to create open spaces for building monumental earthworks, or to increase the productivity of the environment for game animals. These cultural activities had an effect on the environment.

The transition from the Woodland to Late Prehistoric cultures is linked to the introduction of maize agriculture and not to any significant change in climate. Maize, originally grown in Mexico, provided a rich, storable resource that ignited a series of cultural changes across the continent as it made its way north.

Munoz and colleagues convincingly show that periods of change in ecosystems closely correspond to changes in the archaeological record.

The lesson of these data is not that human cultures are determined only by the challenges and opportunities afforded by the environment. Instead, they show that culture is a powerful means of adaptation, which humans have used successfully in the past to survive and thrive during episodes of climate change.

This gives us hope that we can continue to adapt to future changes in climate, whether initiated by natural processes or human activities.
