Was the Sahara Ever a Forest?

The Sahara has been a desert for the last 2–3 million years due to its subtropical latitude and descending Hadley Cell air. However, orbital cycles (precession) periodically strengthened the African monsoon, creating "Green Sahara" phases with savannas, lakes, and rivers—most recently 11,000–5,000 years ago (African Humid Period). It was never a closed-canopy forest, but a grassy, well-watered landscape supporting hippos, crocodiles, and early pastoralists.