ABSTRACT
In this section, we will start with a study of Nepal and Pakistan (which involved me directly) to show how geologists work in the field and to explain a little about why, about 8 million years ago, our far-distant ancestors began leaving their forest homes to adopt a nomadic hunter-gatherer lifestyle. Then we will move on to southern Yemen, to examine oil-industry data which shows quite clearly that what is now a desert was once a complex of rivers, tidal creeks and mud-flats, being flooded by the sea at the time of the dinosaurs, 120 million years ago. The geological history of the area can be worked out in great detail from climatic rhythms encoded in the rocks. The episodic flooding of the flat-lying coast by the rising sea was mainly a response to regular changes in climate driven by 100,000-year and 40,000year Milankovitch cycles.
