Tracking groundwater offers clues to our ancestors’ migrations and our own gene pool

A new study published in the journal ‘Nature Communications’, suggests that groundwater springs provided a lifeline for the early human migrations out of East Africa, thought to have occurred between 2 million and 1.8 million years ago. At this time African monsoons worked on 23 000-year cycles, varying in their amount of rainfall, with periods of light rain resulting in a shortage of drinking water. The research team tracked the flow of African springs at various time periods, which enabled them to map the route that these populations would likely have taken and may help explain puzzling anomalies in dispersal patterns.

In addition to the impact of climate fluctuations, this work highlights the contributory role that geology also plays in making drinking water available. As the lead author of the study Dr Mark Cuthbert explains in the paper, ‘We found that the geology is really important in controlling how much rainfall gets stored in the ground during wet periods. Modelling the springs showed that many could still flow during long dry periods because this groundwater store acts like a buffer against climate change.’

Intriguingly, the team also conjecture that the springs are likely to have functioned as forms of community hubs for traveling populations. By offering an opportunity for people to gather, these springs ultimately increased genetic diversity and so provided a spur to human evolution.

The role of groundwater-surface water interactions

This latest research, illuminating the lives of our ancestors, draws on the techniques and findings of the EU-funded EPHEMERAL project, completed in 2015. This research looked at how groundwater-surface water interactions (GSI) regulate indirect recharge in ephemeral stream catchments, only flowing for short periods of time (usually somewhere between hours to days).

The EPHEMERAL team was also led by Dr Cuthbert and used innovative computational modelling techniques to process information derived from detailed field monitoring and analysis of a catchment in New South Wales (NSW), Australia. The work investigated the natural processes whereby surface water percolates downward to recharge groundwater. An improved understanding of the process, alongside the modelling, allowed the exploration of future scenarios responding to variables such as land-use and climatic changes. Crucially, the work was designed to be transferable to other catchments.

The groundwater in aquifers is replenished by surface water from rivers and streams, as well as from precipitation. It functions as an underground reservoir for the storage of water that can mitigate surface water shortages for example during droughts. About 20% of the world''s fresh water supply comes from groundwater, which is believed to supply drinking water to around a third of the global population. Additionally, according to a recent report in Nature, groundwater also supplies just over 40% of the water used to irrigate the world’s food supply.

However, concerns are growing that with water scarcity increasing in parts of the world, due to factors such as climate change, urbanisation and population growth, reliance on groundwater (as well as alternative sources such as wastewater) will inevitably grow. By highlighting the role that geology has played in meeting human demand for water in the past and modelling possible scenarios for groundwater-surface water interactions, EPHEMERAL has contributed to a better understanding of the requirements for more sustainable water resource management.

For more information, please see:
CORDIS project webpage