Genealogy in the era of genomics: Models of cultural and family traits reveal human homogeneity

kinetic theory. He is interested in applying the methods of sta tistical physics to revealing pat terns of complexity in social and biological systems. Address for Manrubia: Centro de Astrobiologia, INTA-CSIC, Ctra. de Ajalvir Km. 4,28850 Torrej?n de Ardoz, Madrid, Spain. Internet: cuevasms@inta.es What plain proceeding is more plain than this?" asks the Earl of Warwick in the Shakespearean play Henry VI, Part II. "Henry doth claim the crown from John of Gaunt, the fourth son; York claims it from the third. Till Li onel's issue fails, his [John of Gaunt's] should not reign." In truth, nothing was plain for another two generations, as the ruling family, the Planta genets, nearly butchered themselves into extinc tion during England's 15th-century Wars of the Roses, precipitated by the competing claims of the House of Clarence (descendants of Lionel, third son of Edward III), Lancaster (founded by John of Gaunt, the fourth son) and York (the house of the fifth son, Edmund). The smoke cleared only after Gaunt's descendant Henry VII of Tudor defeated the last Plantagenet king, Richard III, in battle. He consolidated his power with an intra-family marriage to Elizabeth of York. Their son, Henry VIII, was descended from King Edward III (1312-1377) in four different ways?each one marking a key alliance and a turning point in English history. The story of the royal houses of England il lustrates not only how the fate of nations can turn on questions of genealogy but also how the phenomenon of coalescence?the merging of the branches in a family tree?is staggering ly common in any closed population. In fact the Plantagenets are in some ways utterly typ ical. In a population of 1,000 people who choose their mates at random, 10 generations are normally enough to guarantee that any two people have some ancestor in common. Per haps even more startlingly, 18 generations nor mally guarantee that any two people in such a population have all their ancestors in common. So it is not the least bit surprising, for example, that every hereditary monarch in Europe at the beginning of the 20th century was a descen dant of Edward III. In recent years, the field of genomics has revolutionized our perception of how closely all human beings are related to each other. The study of mitochondrial DNA, or mtDNA (passed on without change, except for muta tions, from mother to daughter), and certain genes on the Y chromosome (passed on from father to son) has enabled geneticists to place the time of the "mitochondrial Eve" or the "Y