Past North African humid periods caused expanded vegetation over the Sahara, due to northward tropical African rainbelt displacement, opening migration pathways for hominins. Commonly, these precession-timed humid periods ended within 15,000 years due to rainbelt retreat. During North African humid periods, eastern Mediterranean organic-rich layers called sapropels were deposited at least since 8 Myr. Here we combine climate modelling with palaeoclimate proxy data to show that weakened sapropel preservation during the 5.3–3.3 Myr period resulted from nutrient runoff limitation associated with enhanced North African vegetation cover due to a persistently more northward-located African monsoon front, relative to the mid-Pliocene (3.3–3.0 Myr, when glacial intensity increased). Moreover, sapropel absence within the 3.8–3.3 Myr period coincided with maximum monsoon runoff and extensively humid, vegetated conditions throughout North Africa. Our model results indicate that this 0.5-Myr-long pan-North African humid period ended at ~3.3 Myr because of southward monsoon front displacement with Northern Hemisphere glacial intensification. The 3.8–3.3 Myr humid period coincided with the earliest known evidence for hominin coexistence over eastern and central North Africa. We posit that persistent green corridors during this humid phase facilitated early hominin connectivity and migration, expanding their habitat range over the wider North African territory.

过去的北非潮湿时期，由于热带非洲雨带向北移动，导致撒哈拉沙漠上空植被扩张，为古人类的迁徙开辟了道路。通常，由于雨带退缩，这些岁差湿润期会在 15,000 年内结束。在北非潮湿时期，东地中海富含有机物的层（称为腐泥）至少从 8 密尔开始沉积。在这里，我们将气候模型与古气候代理数据相结合，表明 5.3-3.3 Myr 时期腐泥保存的减弱是由于营养物径流限制造成的，而养分径流限制与北非植被覆盖的增加有关，这是由于非洲季风锋相对于中期而言持续偏北。 -上新世（3.3–3.0 Myr，当冰川强度增加时）。此外，3.8-3.3 密尔期间腐泥的消失恰逢季风径流最大和整个北非的广泛潮湿、植被条件。我们的模型结果表明，由于季风锋向南移动以及北半球冰川强化，这段长达 0.5 密尔的泛北非湿润期在约 3.3 密尔结束。 3.8–3.3 Myr湿润时期与已知最早的人类在北非东部和中部共存的证据相一致。我们认为，在这个潮湿的阶段，持续的绿色走廊促进了早期人类的连通和迁徙，将他们的栖息地范围扩大到了更广阔的北非领土。