Mediterranean from the Atlantic. The seawater in the Mediterranean 

 basin then dried out completely, depositing over one million cubic 

 kilometres of sea salt, which, as Ryan (1973) pointed out, constitutes 

 about 6% of the dissolved salts in the world's oceans; its removal 

 from circulation must have resulted in a significant freshening of 

 sea water that would have facilitated the formation of sea-ice near 

 Antarctica. The Messinian salinity crisis had striking physical and 

 biological consequences, as were first described by Hsu et al. (1977). 

 For instance, a dry-land connection was opened between Africa and 

 Europe, facilitating the free exchange of fauna and flora, while the 

 cool, arid climate around the desiccated Mediterranean might well 

 have promoted an early expansion of African savannas (Brain, 

 1984). The evidence further suggested that the connection between 

 the Atlantic and the Mediterranean Oceans was re-established 

 abruptly at about 5 million years ago, which brought the salinity 

 crisis to an end. 



It had long been surmised that the Terminal Miocene Event was 

 precipitated by the sudden establishment of the west Antarctic ice 

 cap and its linkup with the long-standing east Antarctic equivalent. 

 While this concept still seems to be current, the situation has been 

 complicated by evidence of tectonic activity, active rifting, and the 

 rise of the Transantarctic Mountains (Denton, 1995, Cande et al., 

 2000). 



The next important event in the cooling trend was the onset of 

 the first Northern Hemisphere glaciation, which is currently placed 

 at about 2.54 million years ago (Clark et al., 1999). This trend was 

 accompanied by the regular glacial-interglacial cycles that have been 

 such a prominent feature of more recent times, first with a period- 

 icity of 41 thousand years until about 1 million years ago, followed 

 by the establishment of the 100-thousand-year cycles, into which we 

 are still currently locked. In Africa, the effects of cooling on habitats 

 was greatly enhanced by volcanic activity and tectonic movement; 

 in East Africa, combined effects of the rift valley development, as- 

 sociated volcanoes and regional uplift were striking, while, in south- 

 ern Africa, uplift of between 600 and 900 meters along the eastern 

 regions may have had as much effect itself as the superimposed 

 global cooling trend (Partridge et al., 1995). 



