Arabia's Ancient Green Past: New Study Reveals Rivers, Hippo Habitats, and Human Migration Routes

Recent research indicates that the Arabian Peninsula, now largely desert, experienced multiple "green phases" over the past eight million years, facilitating animal and early human migration between Africa and Eurasia. A study published in *Nature* analyzed cave formations (speleothems) from seven cave systems in central Saudi Arabia, revealing at least eight distinct humid periods from the late Miocene (approximately 7.5 million years ago) to the late Pleistocene (less than 200,000 years ago). The Saudi Heritage Commission also unveiled findings this week that confirm the Kingdom was a vital oasis eight million years ago. The research team, including Hubert Vonhof from the Max Planck Institute for Chemistry, used dating methods and analyzed water droplets trapped within calcite crystals to determine the origin of ancient rainfall. The oldest formations resulted from summer monsoon rains from the south, while more recent ones showed influence from winter storms from the Mediterranean. Monika Markowska, the study's lead author, noted a gradual decrease in rainfall during wetter intervals over the last eight million years, leading to increased aridity. Fossil discoveries support these findings. The Baynunah Formation in the United Arab Emirates (6-8 million years old) contains fossils of water-dependent animals like hippos and crocodiles. Similarly, Saudi Arabia's Nefud Desert has yielded Pleistocene fossils of water-dependent species and stone tools, indicating human presence. Dr. Faisal al-Jibrin of the Heritage Commission emphasizes Arabia's central role in mammalian and hominin migrations. The study is part of the Green Arabia Project, which aims to explore the region's natural and environmental history.