How did humans become human? Understanding when, where and in what environmental conditions our early ancestors lived is central to solving the puzzle of human evolution.

Unfortunately, pinning down a timeline of early human evolution has long been difficult – but ancient volcanic eruptions in East Africa may hold the key.

Our new study, published in Proceedings of National Academy of Sciences, refines what we know about volcanic ash layers in Turkana Basin, Kenya. This place has yielded many early human fossils.

We have provided high-precision age estimates, taking a small step closer to establishing a more refined timeframe of human evolution.

The Great Rift Valley in East Africa is home to several world-renowned fossil sites. Of these, the Turkana Basin is arguably the most important region for early human origins research.

This region is also within an active tectonic plate boundary – a continental rift – that has triggered volcanic eruptions over millions of years.

As early humans and their hominin ancestors walked these Rift Valley landscapes, volcanic eruptions frequently blanketed the land in ash particles, burying their remains.

Over time, many fossil layers have become sandwiched between volcanic ash layers. For archaeologists today,........

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