Chapter 2 examines an ‘agricultural revolution’ in the rural areas around Lake Tanganyika’s emporia, characterised by changes in labour regime, crop choice, and land-use. It uses climatological sources and the wider context of the Indian Ocean monsoon system to examine how the introduction of new crops (cassava, maize, and rice) affected agricultural productivity and vulnerability to the effects erratic climatic conditions, including droughts and floods. It argues that benign environmental conditions in the Indian Ocean World during mid-century contributed to the viability of large port-towns. However, erratic rainfall from 1876 onwards, the replacement of East African staples with less drought-resistant crops, and the increased demands on the region’s agricultural supplies from emporia and the caravan trade exacerbated trends towards violence and instability during the late 1870s and 1880s.

Some 10,000 years ago, agriculture arose independently in several areas across the world. The causes of the agricultural transition are still debated, but it is likely that the unprecedented warmth and stability of the Holocene climate made agriculture possible and that the climate instability of the Pleistocene made it impossible. As the weather became more predictable, people began to more intensively manage wild plants and began to store the grain they collected. Because of the unpredictability of harvests, people cultivated more crops than they thought they would need, and in most years, there was a surplus of food, leading to larger and more concentrated populations. By 5,000 years ago, small-scale agriculture had led to large-scale state-managed economies and total dependence on agriculture. Competition between city-states gave us full-blown ultrasocial economies and hierarchical, repressive states. Other consequences of agriculture for individuals include a marked decline in physical health, a reduction in brain size, and a loss of individual autonomy.

First, we show that simple geographic forces play a role in understanding differences in current prosperity and income. This can be partially traced back to deep roots, such as the Agricultural Revolution, which allowed for a transition from a hunter-gatherer society to a farmer society and enabled the building of institutions (this gave the Eurasian continent a head start). Second, we analyse the importance of geo-human interaction for explaining current prosperity levels. There is special attention for the role of embodied institional knowledge incorporated in international migration flows for helping us understand the ancestry-adjusted impact of bio-geographic and institutional factors (which helps explain the reversal of fortune hypothesis). Eventually, bio-geographic factors are thus important for economic development levels, either directly or indirectly through geo-human interaction.

First, we show that simple geographic forces play a role in understanding differences in current prosperity and income. This can be partially traced back to deep roots, such as the Agricultural Revolution, which allowed for a transition from a hunter-gatherer society to a farmer society and enabled the building of institutions (this gave the Eurasian continent a head start). Second, we analyse the importance of geo-human interaction for explaining current prosperity levels. There is special attention for the role of embodied institional knowledge incorporated in international migration flows for helping us understand the ancestry-adjusted impact of bio-geographic and institutional factors (which helps explain the reversal of fortune hypothesis). Eventually, bio-geographic factors are thus important for economic development levels, either directly or indirectly through geo-human interaction.