What was the historical state of the ecosystem?

• Only a few thousand years ago the Sahara was significantly wetter, and a significant large mammal fauna resided in this area.
• The extreme aridity of this area is a relatively recent feature. Much larger areas of the Sahara had adequate water only 5000 to 6000 years ago. It is not clear how much of this ecoregion was covered with vegetation, but in other parts of the Sahara the vegetation was closer to the savanna woodlands of eastern and southern Africa.
• During the Mesozoic much of North Africa was under water and marine deposits were deposited. The area was uplifted in the Middle Tertiary and has been eroding ever since.
• During the last glaciation, it was bigger than it is today because precipitation in the area was low. But from 8000 BCE to 6000 BCE, precipitation in the desert increased because of the development of low pressure over ice sheets to its north. Once these ice sheets melted however, the low pressure shifted and the northern Sahara dried out but the south continued to receive moisture due to the presence of a monsoon.
• Around 3400 BCE, the monsoon moved south to where it is today and the desert again dried out to the state it is in today.
• At the end of the last Ice Age, the Sahara Desert was just as dry and uninviting as it is today. But sandwiched between two periods of extreme dryness were a few millennia of plentiful rainfall and lush vegetation.
• BUT around 10,500 years ago, a sudden burst of monsoon rains over the vast desert transformed the region into habitable land.
• This opened the door for humans to move into the area, as evidenced by the researcher's 500 new radiocarbon dates of human and animal remains from more than 150 excavation sites.
• During these few thousand years, prehistoric humans left the congested Nile Valley and established settlements around rain pools, green valleys, and rivers.
• In the Egyptian Sahara, semi-arid conditions allowed for grasses and shrubs to grow, with some trees sprouting in valleys and near groundwater sources. The vegetation and small, episodic rain pools enticed animals well adapted to dry conditions, such as giraffes, to enter the area as well.
• In the more southern Sudanese Sahara, lush vegetation, hearty trees, and permanent freshwater lakes persisted over millennia. There were even large rivers, such as the Wadi Howar, once the largest tributary to the Nile from the Sahara.