The Aboriginal tribes in southern Australia, who could be the direct descendants of migrants who left Africa up to 75,000 years ago, and who carry some of the genes associated with the Denisovan (a species of human related to but distinct from Neanderthals) peoples of Asia; and having them migrated from Siberia to tropical parts of Asia and that they interbred with modern humans in South-East Asia 44,000 years ago, before Australia separated from Papua New Guinea.
Discharge fluctuation of major rivers
Fluvial geomorphology provides useful evidence for changes of the hydrological balance in semiarid or and regions. Specifically, well-dated, fine-grained alluvial fills in semiarid Arizona and New Mexico suggest that runoff was inhibited by an effective vegetation mat except for brief periods of relative aridity c. 8500-8000 BCE, c. 6500-3800 BCE, and again c. CE 500-1000. In addition, falling water tables are indicated c. 8500-5000 BCE, rising water tables c. 2500-1500 BCE. Comparable deposits may exist in central India and South Africa. In the axis of the Sahara, increased stream activity is indicated c. 7500-6500 BCE and c. 3500-2500 BCE, coincident with periods of significantly higher Nile floods. Alluvial deposits of comparable age elsewhere are either, unstudied, undated, poorly developed, or uninformative. Still enigmatic are alluvial deposits of post-Roman to late medieval age found throughout the Mediterranean Basin, temperate Europe, and western Asia: in part they relate to man-influenced soil erosion, in part they may also reflect climatic variations of uncertain character.
Fragmentary records of Nile flood levels, providing an index of total flood volume and of rainfall in eastern Africa, exist back to 3100 BCE, but few systematic data are preserved before 622 CE. Of particular interest is the downward trend of flood levels after 3000 BCE, culminating in abnormally low floods between 2180-1950 BCE that led to severe famines and allowed sand dunes to invade parts of the former floodplain. A number of surviving records indicate exceptionally high floods c. 1840-1780 BCE and again in the 8th and 7th centuries BCE. On the basis of the gauge readings, Nile floods were abnormally low CE 756-1089, 1192-1382, and 1452-1506; they were unusually high c. 1610, 1727-1776, and 1846-1892; total discharge has been measured regularly since 1870 and shows a sharp decrease since 1899.
Next: The flood, floods and mythic flood stories 10 Animated water