Modelling the role of groundwater hydro-refugia in East African hominin evolution and dispersal

M O Cuthbert,G M Ashley,T Gleeson,M R Bennett,C J Mccormack,A C Newton,S C Reynolds

doi:10.1038/ncomms15696

Abstract

Water is a fundamental resource, yet its spatiotemporal availability in East Africa is poorly understood. This is the area where most hominin first occurrences are located, and consequently the potential role of water in hominin evolution and dispersal remains unresolved. Here, we show that hundreds of springs currently distributed across East Africa could function as persistent groundwater hydro-refugia through orbital-scale climate cycles. Groundwater buffers climate variability according to spatially variable groundwater response times determined by geology and topography. Using an agent-based model, grounded on the present day landscape, we show that groundwater availability would have been critical to supporting isolated networks of hydro-refugia during dry periods when potable surface water was scarce. This may have facilitated unexpected variations in isolation and dispersal of hominin populations in the past. Our results therefore provide a new environmental framework in which to understand how patterns of taxonomic diversity in hominins may have developed.

Highlights

Water is a fundamental resource, yet its spatiotemporal availability in East Africa is poorly understood
Establishing the link between environmental change and resource availability in the East African Rift System (EARS) is a matter of intense debate, the resolution of which is fundamental to understanding hominin evolution as well as patterns of dispersal[1]
Present day conditions in much of the EARS are analogous to relatively dry periods [B70% is arid to semi-arid with groundwater recharge of o50 mm y À 1] and provide a way of exploring the likely hydrological conditions experienced by early hominins

Summary

Introduction

Water is a fundamental resource, yet its spatiotemporal availability in East Africa is poorly understood. Using an agent-based model, grounded on the present day landscape, we show that groundwater availability would have been critical to supporting isolated networks of hydro-refugia during dry periods when potable surface water was scarce This may have facilitated unexpected variations in isolation and dispersal of hominin populations in the past. The potential for widespread groundwater hydro-refugia, such as springs and groundwater-fed perennial streams, has long been neglected; yet it may challenge prevailing views regarding the environmental context for hominin evolution and dispersal We use this perspective to stimulate fresh thinking around the climate-forcing hypotheses, by focusing on how hydrological aspects of the landscape interact with climate change to control water availability, a key resource for survival. The hydro-refugia model shows that early hominins, and later Homo, survival and dispersal is likely to have been facilitated under drier conditions than previously thought possible

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