One of Dr Weiss's former students, Sarah Parcak, of Cambridge University, presented data to the meeting on how a third period of cooling and drying, 4, 200 years ago, destroyed the Old Kingdom of Egypt.
In the Middle East people started to build settlements as early as 15, 000 years ago, a period called the Early Natufian, but a drying of the climate made them nomadic again between 12, 800 and 11, 500 years ago.