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Hereditary surnames contain information about relatedness within populations. They have been used as crude indicators of population structure and migration events, and to subdivide samples for epidemiological purposes. In societies that use patrilineal surnames, a surname should correlate with a type of Y chromosome, provided certain assumptions are met. Recent studies involving Y-chromosomal haplotyping and surname analysis are promising and indicate that genealogists of the future could be turning to records written in DNA, as well as in paper archives, to solve their problems.

Recent discoveries of many new genes have made it clear that there is more to the human Y chromosome than a heap of evolutionary debris, hooked up to a sequence that happens to endow its bearer with testes. Coupled with the recent development of new polymorphic markers on the Y, making it the best-characterized haplotypic system in the genome, this gives us new opportunities to assess its role in disease and selection, through association studies with phenotypes such as infertility and cancers. However, the peculiar genetics of this bizarre chromosome means that we should interpret such studies particularly cautiously.

Shared or different pigmentation is often, sadly, grounds for prejudice among humans. As Steve Jones has pointed out, if blood group of the ABO system were expressed in some discernible form on our skins, we might see some very different divisions between peoples. However, the genetics of human pigmentation has turned out to be a lot more complex than that of blood group. In the world of pigmentation genetics, the mouse is king, with around 100 genes identified as affecting coat colour. By contrast, only one human gene, MC1R, encoding the melanocortin 1 receptor, has clearly been shown to be involved in normal pigmentation. The MC1R gene product acts as receptor for a number of peptides that trigger a complex series of events within cells called melanocytes, leading to the production of the dark pigment eumelanin. Inactivating mutations give rise to the yellow/red pheomelanin. Since 1995, we have known that particular MC1R variants are more likely to be found among people who have red hair, fair skin and who should stay out of the sun. Variants are also associated with melanoma and non-melanoma skin cancer, possibly independently of their role in determining fair skin.It's a matter of common observation that people with fair skin and red hair often have freckles (or ephelides, to give them their correct medical name). Recent work 1xThe melanocortin-1-receptor gene is the major freckle gene. Bastiaens, M. et al. Hum. Mol. Genet. 2001; 10: 1701–1708Crossref | PubMedSee all References1 shows that the MC1R gene is also the major freckle gene −60% of cases of freckles, in people with all hair colours and skin types, are caused by variants in MC1R, emphasizing the pleiotropic nature of mutations in this gene.Another gene, succinctly known as P, lies downstream of MC1R in the pigmentation pathway, and its product might have a role in stabilizing the complex responsible for eumelanin synthesis. Although many mutations in P are known that give rise to abnormal pigmentation in the rare disorder type II oculocutaneous albinism, its role in normal pigmentation has remained unclear. In a study of 184 Tibetans 2xInteraction between the melanocortin-1 receptor and P genes contributes to inter-individual variation in skin pigmentation in a Tibetan population. Akey, J.M. et al. Hum. Genet. 2001; 108: 516–520Crossref | PubMed | Scopus (47)See all References2, skin colour of the upper inner arm was measured as a quantitative trait, and any association with variants in MC1R and P was examined. Neither gene alone showed any association, but a model involving interaction between the genes suggested that particular alleles in combination were influencing skin colour. It seems probable that there are many genes and much pleiotropy in human pigmentation genetics – colour might only be skin-deep, but it could still turn out to be hard to fathom.

Our transition from foragers to farmers, beginning some 10 000 years ago, is arguably the most important revolution in the history of humanity. More food meant expanding populations, and sedentary groups became urban civilizations. The genetic impact of the agricultural revolution in Europe has been intensively studied within modern human populations, but the genes of domesticated animals have their own stories to tell.The animal that our intrepid neolithic ancestors captured and tamed was the formidable aurochs, or wild ox. Previous studies of variation in mitochondrial DNA (mtDNA) sequences showed that the two modern cattle subspecies – the humped Bos indicus, typical of India, and the humpless Bos taurus (Europe and Africa) – are highly diverged from each other and reflect two independent domestications from different aurochs subspecies. Troy et al.1xGenetic evidence for Near-Eastern origins of European cattle. Troy, C.S. et al. Nature. 2001; 410: 1088–1091Crossref | PubMed | Scopus (332)See all References1 have studied mtDNA diversity in modern cattle from Europe, the Near-East and Africa, as well as extinct aurochs, to ask where and when European domestication took place.Four sequences from ∼4000–7000-year-old British aurochs specimens cluster together in a phylogenetic tree and, although most closely related to the Bos taurus group, they are clearly distinct from modern cattle. This suggests that local capture in Britain made little impact on European domestication. Phylogenies of modern cattle sequences from different regions each show ‘star-like’ clusters, indicating population expansions, with time-depths consistent with agriculture's origins. The African cluster is distinctive, suggesting a separate domestication in Africa. In Europe, however, one cluster predominates, whose diversity is greatest in the Middle East and Anatolia, and is reduced towards the north and west, pointing to a Near-Eastern origin for all European cattle.

El Dorado was the mythical kingdom where unimaginable treasures of gold were to be found. Many had heard about it, many died in quest of it, but no-one had actually seen it. The no less exciting, but rather less hazardous, field of human evolutionary genetics has its own El Dorado – a wealth of binary polymorphisms on the nonrecombining region of the Y chromosome, mostly single nucleotide polymorphisms, which we knew had been discovered but could not deploy. Previous studies have used few polymorphisms, and the resolution of the haplotypes they define has been poor. Nonetheless, the potential of the Y chromosome has become clear, with new insights being gained into the origins of modern humans, the peopling of the Americas and Polynesia, the Jewish diaspora and sex-biased gene flow in the European colonizations after 1492, to give but a few examples.Now, the riches are at last before us: Underhill et al. 1xY chromosome sequence variation and the history of human populations. Underhill, P.A. et al. Nat. Genet. 2000; 26: 358–361Crossref | PubMed | Scopus (631)See all References1 present 87 new binary markers and describe the global distribution of 116 haplotypes defined by a total of 167 markers. This approximately quadruples the number of usable, PCR-based polymorphisms and will increase the resolution of Y-chromosomal studies greatly. The population distribution of haplotypes emphasizes the geographical structuring of Y-chromosome diversity: the most ancestral haplotypes are specific to sub-Saharan Africa, consistent with an African origin for modern humans, and many other haplotypes are strongly population specific. Although this property is useful in detecting admixture and mapping population movements, it presents problems of bias when the markers are ascertained – the choice of which population samples are screened for variation can have a major influence on the perceived distribution of diversity in subsequent studies.Semino et al. 2xThe genetic legacy of Paleolithic Homo sapiens sapiens in extant Europeans: a Y chromosome perspective. Semino, O. et al. Science. 2000; 290: 1155–1159Crossref | PubMed | Scopus (535)See all References2 report the application of a subset of these new markers to quantify the relative contribution of Palaeolithic and Neolithic males to modern Europe. Twenty-two markers divide 95% of European Y chromosomes into ten lineages, whose distributions are highly non-random. On the basis of these distributions, ages calculated from microsatellite diversity and relative internal diversities, several of the lineages are assigned either to Neolithic farmers from the Middle East or to peoples who entered during the Palaeolithic and spread after the end of the last Ice Age. Because 22% of European Y chromosomes belong to the ‘Neolithic’ lineages, this is taken to support the view, consistent with mitochondrial DNA data, that the modern population of Europe is about 80% ’. This satisfyingly simple interpretation raises a few questions, however. Estimates of the ages of lineages are notoriously unreliable, and this study is coy with its confidence intervals; also, the idea that Neolithic and Palaeolithic populations shared no lineages and thus that individual markers can be assigned to specific population movements, seems a little too good to be true.Peter Underhill and colleagues have done some great treasure hunting; perhaps now the next El Dorado will be new methods for interpreting the patterns the markers reveal. All that glitters….

Like Noah’s animals themselves, the chromosomes of animals come in matching pairs. The glaring exception to this harmonious scheme is the sex chromosomes: in most mammals the X and Y are very different from each other, but even this odd couple once existed as homologous autosomes. One relic of this past life is the pseudoautosomal region, in which homology is preserved and by which the sex chromosomes continue to pair and recombine.Lahn and Page1xFour evolutionary strata on the human X chromosome. Lahn, B.T. and Page, D.C. Science. 1999; 286: 964–967Crossref | PubMed | Scopus (459)See all References1 have charted this sex-driven process of estrangement by comparing the sequences of 19 XY-homologous non-pseudoautosomal gene pairs that represent molecular fossils of the autosomal past. They examined the divergence between X and Y coding sequences at synonymous sites, which do not alter amino acids, and which should therefore be neutral. The gene pairs fell neatly into four independent classes, and, when chromosomal location was examined, the X-linked members of each class corresponded with a cluster, or ‘stratum’. Synonymous nucleotide divergence provides a measure of time, and thus the X-linked genes are stratified along the chromosome by age: the youngest stratum is on the distal short arm, adjacent to the pseudoautosomal region, and the strata become progressively older towards the tip of the long arm. This organization suggests that, during sex-chromosome evolution, recombination was suppressed regionally and in discrete steps. Inversions on the Y chromosome where, by contrast, gene order is scrambled, provide an attractive mechanism for this. Recombination suppression was first required around SRY, the novel sex-determining gene on the Y: thus, we expect that its homologue, SOX3, should lie in the most ancient stratum on the X – and it does.