Excavation at Tell Leilan suggests that this site was abandoned soon after the city's massive walls were constructed, its temple rebuilt and its grain production reorganized. The debris, dust, and sand that followed show no trace of human activity. Soil samples show fine wind-blown sand, no trace of earthworm activity, reduced rainfall and indications of a drier and windier climate. Evidence shows that skeleton-thin sheep and cattle died of drought, and up to 28,000 people abandoned the site, presumably seeking wetter areas elsewhere. Tell Brak shrank in size by 75%. Trade collapsed. Nomadic herders such as the Amorites moved herds closer to reliable water suppliers, bringing them into conflict with Akkadian populations. This climate-induced collapse seems to have affected the whole of the Middle East, and to have coincided with the collapse of the Egyptian Old Kingdom.