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The Genetic History and Diversity of Humanity

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The Genetic History and Diversity of Humanity RMA thesis Marieke Drost - Historical and comparative studies of the sciences and humanities - Utrecht University The genetic history and diversity of humanity History, identity and meaning in the Human Genome Diversity Project and the Genographic Project July 2011 2 Contents Thank you.......................................................................................................................................................... 4 Introduction - The genetic history and diversity of humanity ........................................ 5 Chapter one - Researching human history and diversity after World War II ........... 14 The UNESCO Statements ....................................................................................................................... 14 Cavalli-Sforza’s trees ............................................................................................................................... 22 Lewontin’s measurements .................................................................................................................... 31 Methods and technologies .................................................................................................................... 34 African Eve .................................................................................................................................................. 36 Chapter two - Cavalli-Sforza and the Human Genome Diversity Project: vanishing opportunities .................................................................................................................................. 41 The Human Genome Diversity Project ............................................................................................. 41 Cavalli-Sforza ............................................................................................................................................. 47 View of history .......................................................................................................................................... 51 Unity .............................................................................................................................................................. 55 Trees .............................................................................................................................................................. 59 Maps .............................................................................................................................................................. 65 Chapter three - Criticism and controversy ........................................................................... 69 Modelling history ..................................................................................................................................... 69 Essentialism ............................................................................................................................................... 78 The indigenous .......................................................................................................................................... 88 Challenging Lewontin ............................................................................................................................. 94 Commercial ancestry testing ............................................................................................................ 103 Chapter four - Spencer Wells and the Genographic: songlines for humanity ....... 111 The Genographic Project .................................................................................................................... 111 The journey of man .............................................................................................................................. 116 Narrativisation ....................................................................................................................................... 122 Identifying groups ................................................................................................................................. 125 Models and methods ............................................................................................................................ 131 Chapter five - Criticism continued – or not ........................................................................ 138 Conclusion .................................................................................................................................... 151 3 Thank you Thank you Bert, for superb supervising, for always letting me make my own decisions, and for the extensive off-topic chats. Thank you Peter Koolmees for ploughing through one hundred and seventy pages. Thank you Paula for never hesitating to support me. If ever I had a model of perseverance in the face of difficulties it was you. Thank you Hans, for your wise mentoring and for always answering the phone. Thank you Anneke for down-to-earth advice and delicious dinners. Thank you Wim for your stringent warnings not to give up. Thanks to all my parents for their mental and financial support. Thank you Matthea for sharing and sparring. I honestly miss living with you in the library. Thank you Marieke for moral support, rum and chocolate mousse. Thank you Anne for your critical views. Thank you Mathieu for unconditionally tolerating a worn out master student. Thank you opa Herman for supporting, although you did so without knowing. Thank you Nel. Thank you little brother and sister. Thank you Nelley for long- distance encouragement and for saving the soap. Thank you Joes for feedback and coffee breaks. Thank you Neeltje and Mienke and Huug and Merel and Nicolas and Onno. Thank you Han and Simon for the sailing breaks. Thank all of you in Groningen for the hot baths and soup. Thank you Annemarieke for administrative calamity management. And thank you teachers and classmates, in London and in Utrecht, for inspiration. 4 Introduction - The genetic history and diversity of humanity As far back as the written historical record can be traced, and probably well before that, people have invented stories about the origins and ancient history of humans. In modern times, with the emergence of such natural-historical sciences as palaeontology, evolutionary biology, archaeology and anthropology, stories about man’s origins and spread across the earth left the realm of the mythic and metaphysical world views, and often contributed to their decline. The new origin stories were the products of the scientific study of bones, fossils, and animal and human morphology. Biblical history made way for evolutionary narratives that stretched the timeline to unprecedented lengths. They were often framed in contrast with their religious precursors, so that in a sense, the dichotomy between the two world views was itself a product of the new evolutionary paradigm. In the twentieth century, genetics joined the scientific effort to uncover the “deep history” of humanity. Population geneticists started to study patterns in global genetic variation - irregularly distributed genetic differences and similarities, called ‘polymorphisms.’ By mapping these, geneticists tried to establish the relations between currently living populations. The differences and similarities they found were interpreted in terms of group descent, and used to reconstruct diasporic histories of humanity. In this way, geneticists built humanity’s family tree, or rather, lots of tentative versions of it. They interpreted the genetic variation in the present human gene pool as an echo of ancient population movements, splits, bottlenecks and expansions. They produced images, models and narratives. The former include geographic maps depicting the migration of human groups, identified by genetic markers, across the world, and phylogenetic trees. Phylogenetic analysis reconstructs the history of groups or organisms. Trees depict these groups as branches on a tree. The variation in frequencies of genes found in present populations informs both trees and maps. A high frequency of a specific marker in a specific region of the world ties it to that location. With the help of dating methods, based on average mutation rates, geneticists calculate when the marker first emerged as a mutation in an individual’s genome. By mapping the occurrence of markers around the world, associating them with specific regions and with different times of origin, the tree 5 of humanity is constructed. Markers that occur in high frequencies in specific populations are visualised as separate branches on the tree, while similarities between the genetic make ups of groups indicate shared origins. With such research, genetics contributed to the changing of explanations of variation itself. From the nineteenth century onwards, traditional philosophical and religious explanations of human physical variation were supplanted by biological ones; the sons of Noah were replaced by the great apes. Initially, the focus lay on morphological variation. When Darwinian evolutionary theory was merged with Mendelian genetics in the twentieth century, the level of analysis slowly shifted from physical to genetic variation. Evolutionary theory explained variation in terms of population and migration history, as the result of dynamic and ongoing processes of intermixing and separation. Therefore, any patterning of the human gene pool was seen as a temporary phase in the dynamic, tens of thousands of years long population history of humanity. Nevertheless, on
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