Around 5,000 to 6,000 years ago the entire North African region, including the vast majority of the Sahara desert was covered in flourishing lakes and greenery, with a complex ecosystem that featured diverse fauna, including several herbivores, predators and even primates. What happened next may be the single most significant environmental catastrophe in the history of the earth, the cause of which continues to be debated hotly among earth scientists.

As the earth slowly moved into the Holocene era of its existence a number of factors converged to cause a prolonged and catastrophic dry spell in North Africa.

- The slow shift in the earth's axis and rotation resulted in the North African region coming out of the wet zone around the equator, which resulted in a reduction in the monsoons that brought so much rain to North Africa in the preceeding thousands of years.

- The earth had just come through an Ice Age, which involved the earth's axis being at an extreme tilt, making for more pronounced seasons. Over time the tilt gradually corrected itself, leading to less pronounced wet and dry seasons.

- The earth also moved into a period known as the Mid-Holocene Drought between 5,000 and 8,000 years ago. This coincided with the Sahara region coming out of the wet equatorial zone, exacerbating the conditions for prolonged drought.

- Human habitation of the region contributed to vegetation cover loss, with large areas cleared for farming and agriculture, further decreasing the region's ability to capture and retain water.

All these factors combined to eventually turn a once fertile and green expanse of land into the world's largest hot desert.