Evidence of Lévy walk foraging patterns in human hunter–gatherers

David A. Raichlena, Brian M. Woodb, Adam D. Gordonc, Audax Z. P. Mabullad, Frank W. Marlowee, and Herman Pontzerf

Edited by Simon A. Levin, Princeton University, Princeton, NJ, and approved November 22, 2013 (received for review October 2, 2013)

Significance

Lévy walks are a random walk search strategy used by a wide variety of organisms when searching for heterogeneously distributed food. This type of search involves mostly short move steps (defined as the distance traveled before pausing or changing direction) combined with rarer longer move steps. Here, we show that the Hadza, hunter–gatherers from northern Tanzania, perform Lévy walks when foraging for a wide variety of food items, suggesting that Lévy walks are an important movement pattern for the most cognitively complex foragers on Earth. Our results suggest that scale-invariant, superdiffusive movement profiles are a fundamental feature of human landscape use, regardless of the physical or cultural environment, and may have played an important role in the evolution of human mobility.

Abstract

When searching for food, many organisms adopt a superdiffusive, scale-free movement pattern called a Lévy walk, which is considered optimal when foraging for heterogeneously located resources with little prior knowledge of distribution patterns [Viswanathan GM, da Luz MGE, Raposo EP, Stanley HE (2011) The Physics of Foraging: An Introduction to Random Searches and Biological Encounters]. Although memory of food locations and higher cognition may limit the benefits of random walk strategies, no studies to date have fully explored search patterns in human foraging. Here, we show that human hunter–gatherers, the Hadza of northern Tanzania, perform Lévy walks in nearly one-half of all foraging bouts. Lévy walks occur when searching for a wide variety of foods from animal prey to underground tubers, suggesting that, even in the most cognitively complex forager on Earth, such patterns are essential to understanding elementary foraging mechanisms. This movement pattern may be fundamental to how humans experience and interact with the world across a wide range of ecological contexts, and it may be adaptive to food distribution patterns on the landscape, which previous studies suggested for organisms with more limited cognition. Additionally, Lévy walks may have become common early in our genus when hunting and gathering arose as a major foraging strategy, playing an important role in the evolution of human mobility