Who We Are and How We Got Here: Ancient DNA and the new science of the human past by David Reich

Who We Are and How We Got Here: Ancient DNA and the new science of the human past by David Reich
My rating: 4 of 5 stars

Fascinating and revelatory, its rather technical initially, even for a medico like me. Archaeological findings lead to conjecture and extrapolation about historical facts about human evolution and migration but genomic analysis provides a definitive pre-history of mankind.
Here is the arrival of crops to the Indian sub-continent where the existing humans were hunter-foragers

The Indian subcontinent is one of the breadbaskets of the world – today it feeds a quarter of the world’s population… The Near Eastern winter rainfall crops, wheat and barley, reached the Idus Valley sometime after nine thousand years ago… Around five thousand years ago local farmers succeeded in breeding crops to adapt to monsoon summer rainfall patterns, and the crops spread into peninsular India. The Chinese summer rainfall crops of rice and millet also reached peninsular India around five thousand years ago. Indian may have been the first place where Near Eastern and the Chinese crop systems collided.

An overview of the caste system in India

How the varna and jati relate to each other is a much-debated mystery… Thousands of years ago, Indian peoples in effectively endogamous tribal groups that did not mix, much like the tribal groups in other parts of the world today. Political elites then ensconced themselves at the top of the social system (as priests, kings and merchants), creating a stratified system in which the tribal groups were incorporated into society as Shudras and Dalits. The tribal organization was thus fused with the system of social stratification to form early jati, and eventually the early jati, and eventually the jati structure percolated up to the higher rans of the society, so that today there are many jati of higher as well as of lower castes. These ancient tribal groups have preserved their distinctiveness through the caste system and endogamy rules.

India may now be the most populous nation but

The Han Chinese are truly a large population, They have been mixing freely for thousands of years. In contrast, there are few if any Indian groups that are demographically very large … India is composed of a large number of small populations.

Laying to rest the controversy of Arya Invasion/migration

The Ancient North Indians (ANI) were a mixture of about 50% steppe ancestry related distantly to the Yamnaya, and 50% Iranian farmer-related ancestry from groups the steppe people encountered as they expanded south. The Ancient South Indians (ASI) were also mixed, a fusion of a population descended from earlier farmers expanding out of Iran (around 25% of their ancestry), and previously established local hunter-gatherers of South Asia (around 75% of their ancestry.

Other nationalist narratives

The Nazi ideology of a “pure” Indo-European-spealing Aryan race with deep roots in Germany, traceable through artifacts of the Corded Ware culture, has been shattered by the finding that the people who used these artifacts came from a mass migration from the Russian steppe, a place that German nationalists would have despised as a source. The Hindutva ideology that there was no major contribution to Indian culture from migrants from outside South Asia is undermined by the fat that approximately half of the ancestry of Indians today is derived from multiple waves of mass migration from Iran and Eurasian steppe within the last five thousand years. Similarly, the idea that the Tutsis in Rwanda and Burundi have ancestry from West Eurasian farmers that Hutus do not – an idea that has been incorporated into arguments for genocide – is nonsense. We now know that nearly every group living today is the product of repeated population mixtures that have occurred over thousand and tens or thousands of years. Mixing is in human nature, and one population is – or could be – pure.

But

An outstanding mystery is the ancestry of the peoples of the Indus Valley Civilization, who were spread across the Indus Valley and parts of northern India between forty-five hundred to thirty-eight hundred years ago, and were at the crossroads of all these great ancient movements of people.

The book ends with ethical issues of gene mapping and the future of genomic studies and its fallout – the deeper study of human biology and evolution

A central question in human evolutionary biology is whether human evolution typically proceeds by large mutation frequencies at relatively small numbers of positions in the genome, as in the case of pigmentation, or by small changes in frequencies at a very large number of mutations, as in the case of height

The microbial diseases to which ancient humans succumbed

Ancient pathogen studies have also revealed the history and origin of ancient leprosy, tuberculosis, and, in plants, the Irish potato famine. Ancient DNA studies are now regularly obtaining material from the microbes that inhabit us , including from dental plaque and faeces, providing information about the food our ancestors ate.

A book to be read in small instalments and savoured later.

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