LONDON: Researchers from Northumbria University are making waves with their latest discovery—a collection of ancient stalagmites from caves northeast of Riyadh, Saudi Arabia, is shedding light on a much greener past for the region.

Initially, the scientists aimed to identify humid phases in central Arabia over the past million years that could have transformed this arid landscape into a lush haven, allowing prehistoric mammals and early humans to migrate out of Africa. But their journey took an unexpected twist.

Using radiometric dating methods—specifically uranium-thorium and uranium-lead—researchers faced a shocking first challenge: the stalagmites didn't register the expected ages. Senior research fellow Monika Markowska remarked, "We initially thought the stalagmites might be much younger, and like most scientists, we were baffled when our first method didn't yield any results. But switching to uranium-lead was a game changer." This second technique revealed that these stalagmites are, in fact, a staggering 8 million years old!

This groundbreaking finding has pushed back the timeline of life in central Arabia by over 7 million years. Stalagmites, alongside stalactites and flowstones, form from mineral deposits as rainwater drips through the caves, indicating much wetter conditions in the region's history.

Previously, evidence of climatic conditions in Arabia was limited to only 450,000 years, but recent studies extended this record by another 1.1 million years, indicating 21 distinct periods of increased rainfall.

Markowska highlights that, while southern Arabia had been studied extensively, little was known about conditions further north until now. The latest research opens a window into recurrent humid phases in central Arabia, characterized by an abundance of water and vegetation.

The caves in Al-Sulb Plateau, chosen for this study, feature signs of stalagmite growth, hinting at a much wetter climate than what exists today. "It’s fascinating how these formations tell a story of a landscape that was once flourishing, contrasting with today's hyper-arid conditions," Markowska stated.

The 22 stalagmites analyzed from seven cave systems unveiled a sequence of humid episodes spanning 6.25 to 7.44 million years ago. This timeframe coincides with the Late Miocene, a period when rich fossil evidence exists in the UAE, showcasing a thriving ecosystem complete with elephants and saber-toothed cats.

Researchers speculate that the rain feeding these ancient river systems likely originated from central Arabia. With a lack of fossil evidence from deserts, it’s now clear that the region may have served as a vital corridor for species migrating between Africa and Eurasia.

The monumental nature of this discovery is underscored by contributions from a global team, including researchers from leading universities and organizations in the UK, Germany, Switzerland, Australia, and the US. Their collaborative effort has provided invaluable support for expanding our understanding of Arabia’s ancient climate.

While fossil records remain sparse, with significant finds limited to the Baynunah Formation in the UAE and the Nefud Desert in Saudi Arabia, the researchers remain optimistic. Markowska emphasizes, "Just because we haven't found more fossils yet doesn't mean they weren't there. Our new findings suggest Arabia could have been an unrecognized hotspot for biogeographical exchange over the last 8 million years."

As the researchers plot their next steps, the focus will shift to understanding the types of vegetation that thrived during these humid periods. By extracting ancient pollen trapped in the stalagmites, they aim to reconstruct the ecological landscape of what was once a verdant Arabia.

"This vegetation research is our next big adventure. It could reveal the rich biodiversity that once flourished here and the herbivores—along with their predators—that roamed the land," Markowska added with enthusiasm.