Food web structure during the European Pleistocene

Several models that have been proposed for explaining human evolution involve human-carnivore relationships. Reconstructing the structure and functioning of past food webs is, therefore, essential for evaluating the assumptions and conclusions of these models. Here we present a preliminary attempt to reconstruct the structure of some Pleistocene food webs from the Iberian Peninsula and to compare them with recent food webs from several regions and environments. The present work is a first step towards the reconstruction of past food web dynamics and is aimed at gaining a better understanding of the role of humans in past food webs. Our analysis was restricted to mammals weighing more than 10 kg because they constitute the portion of the food web that allegedly included hominins. Predator-prey interactions for fossil species pairs are inferred from their body sizes, evidence from the fossil record and behavioural information from close living relatives. The number of potential prey per predator in Pleistocene and recent food webs is compared, and the relationship between the number of secondary consumers and the standing biomass of primary consumers, estimated using allometric relationships, is investigated. Pleistocene food webs show a distinctive architecture, with a relatively large number of secondary consumers and a small number of primary consumers. In addition, the size distribution of primary consumers also differs between recent and Pleistocene food webs. Our results point to high intraguild competition during the Pleistocene, especially during the Early Pleistocene, which may have conditioned resource availability for Paleolithic hunter-gatherer populations.