Surname studies with genetics--论文代写范文精选

它是一个次要的问题,一些统计是新兴的数据,有局部的争议是否大的家谱能解释一夫多妻的孩子,这是一种特定争论争论。我将面临这一个问题，关于考虑书面证据,或DNA姓氏的起源。下面的paper代写范文继续讲述。

Introduction 
The study of surnames has long involved linguistics, history and genealogy; now, genetics also can feature. Geneticists have been interested in surnames for over a century.1 Recent advances have honed a fresh tool for investigating surnames, though some of its revelations remain subject to debate. Rather like surnames, Y-chromosomes descend only down male lines. Looking to the benefits, George Redmonds commented, ‘The potential the Y chromosome has to identify relationships [between men], confirming or disproving linguistic theories [for surnames], should not be underestimated’.2 As yet, Y-chromosomal DNA (Y-DNA) studies of a surname’s Old World3 development are relatively few; and, some in the Guild of One Name Studies reserve judgement.4 Even so, the number of Guild members with formative Y-DNA projects is rising; such projects grew from one in 1997 to one hundred and forty-five by July 2008.5 Most combine Y-DNA testing with detailed documentary evidence. 

Also, a recent scientific study has assessed Y-DNA data alone6 seeking onomastic patterns for forty English surnames, which were compared with twenty-eight Irish surnames. Along with outlining this developing field, I shall describe two Y-DNA case studies, for the surnames Meates and Plant. The Meates project has made direct use of the primary power of Y-DNA to identify matching individuals. It is a secondary matter that some statistical evidence is emerging, from other Y-DNA studies, indicating that some male-line families are unusually large. There is a topical controversy about whether such families might best be explained by large numbers of polygynous children; and, I shall illustrate that debate with a particular controversy about the Plant surname. I shall prefix this with an account of the problems faced when considering either the documentary evidence, or DNA evidence, for the origins of surnames.

Developing genetic techniques 
The unveiling of the molecular structure of DNA in the 1950s7 led on to the identification of distinctive Y-signatures for men. A Y-signature is a set of values for certain markers in the DNA of a man’s Y-chromosome. Mainly two types of marker are used; these are denoted SNP and STR. SNP denotes a single nucleotide polymorphism, which is the mutation of one base pair in the double-helical structure of DNA. The base pairs are sub-molecular units that join together the two molecular backbones of the double helix; each base is of one of four types (denoted C, G, A and T). A set of Y-chromosomal SNP markers (YSNPs)8 represents mutations that can occur to the sequence of the bases. 

However, these markers vary too rarely9 to be very useful for surname studies. Y-SNPs are used more for deep ancestry studies of human populations, dating back many millennia. STR markers in the Y-chromosome10 (Y-STRs) are more useful for surname studies. They mutate much more often than Y-SNPs and provide far more distinctive Ysignatures.11 STR denotes a short tandem repeat, which is the repetition of a sequence of bases in the DNA structure; the number of these repeats changes slightly occasionally in the male line descent of the Y-chromosome. If sufficiently many YSTR markers are measured, slightly different Y-signatures can be obtained for men descended down different, genetically intact branches of a one name, genealogical tree. Errors or hidden infidelities in the tree can be revealed by identifying those men whose Y-signatures do not match closely together. 

The first SNP markers located on the Y-chromosome were discovered in the mid- 1980s; and, by the 1990s, they were in regular use. By the turn of the millennium, comparisons were being made of the Y-STR markers of men with the same surname. Though barely a decade old, a study of random bearers of the Sykes surname12 now seems dated, not least because the lengths of only four Y-STR markers were measured for each man. Now, twelve, seventeen, twenty-five, thirty-seven, or sixtyseven Y-STR markers are typically measured to identify a Y-signature more distinctly. When more markers are measured, the study is said to be ‘higher resolution’ though this may not be necessary for a Y-signature that is already rare in the general population at a lower resolution.

A pioneering Y-STR study: Sykes 
Though seminal, the Sykes study has been superseded. Nonetheless, it provides an historic backdrop and serves to introduce some relevant concepts. On the basis of a low resolution study by Sykes and Irven, the English surname Sykes can be described to be a single ancestor featured name. That is to say that its Y-STR results were found to display a single, significant cluster of matching Y-signatures (i.e. a significant ‘Y-cluster’). This Y-cluster, found for the tested Sykes men, did not occur in the general population, as was checked with a small control sample of random men. An interpretation of the Y-clustered results can proceed as follows. 

One can consider that there have been egressions of a characteristic Sykes Y-signature (or slight mutations of it) to other surnames, because of male philandering for example.13 As a corollary, there will have been male introgressions of markedly different Y-signatures from other surnames into the population of a main Sykes family. Early male introgressions could split an initial Y-cluster into a few. In the case of the experimentally observed, single Y-cluster for Sykes, the results indicate more surely than would several Y-clusters that many of the living Sykes men have descended down male lines from a single, eponymous, male ancestor. One can theoretically expect that around half of the randomly selected, modern bearers of a populous, single family surname will remain free of ancestral introgressions, after allowing twenty-five generations for the introgressions to accumulate (Appendix A). 

This agrees broadly with the published experimental finding for Sykes that 43.8% of the tested men matched into its observed Y-cluster, albeit that this carries a statistical uncertainty14 of 7%. The Sykes Y-mismatches were found to occur singly – that is, they did not match with any other Sykes Y-mismatch, or with the Y-cluster, in the small sample of living Sykes males. The Y-mismatches were attributed solely to the accumulated effects of male introgressions. In their account of their study, Sykes and Irven commented, ‘This points to a single surname founder for extant Sykes males’. It is important to note however that this finding for living males does not prove that there was a ‘single origin’ for all of the initial bearers of this populous surname since, for example, there could initially have been other Sykes families, which died out.

The uncertain origins of surnames 
Various hypotheses have been considered for the origins of a surname15 – ‘multiple origins’; ‘plural origins’; ‘single origin’ – with the term ‘plural origins’16 covering the possibility of a few origins, rather than one or many. There is an alternative terminology. With a hedge that ‘in surname research there are very few certainties’, Hanks used genetic in terms such as ‘monogenetic’ which he related to a surname’s early locations.17 He explains18 that the polygenetic hypothesis is that a surname was ‘coined independently in many different places’; whereas, monogenetic is for one ‘derived from just one original bearer at one particular place and time’. 

Here I use instead the terms such as ‘single origin’ and reserve genetic for more scientific flavours to this word though not particularly just biological ones.19 Another academic discipline should not be ignored. Linguistic interpretations can often provide clues as to how a surname was coined. A common occupation such as ‘smith’ could have given rise to many origins to a surname in contrast to more likely a single origin as can be expected for a surname derived from a uniquely named, small village for example. 

Other times however, the linguistic evidence is ambiguous. Y-STR evidence holds best for modern times. Exhuming old remains for a surname is widely regarded as sacrilegious. In any event, Y-STR measurements are problematic when using degraded DNA. Studying old remains is yet generally restricted to identifying a few, very low resolution, Y-SNP markers. However, genealogies can be attached to the Y-STR results of living descendants, such that an earlier forefather can be allocated a Y-signature. The Y-STR evidence can sometimes help with extrapolating back further towards a surname’s origins, by identifying ancestral Ymatches between widely spread instances of a surname. 

The geographical modelling can also take account of documentary evidence for a surname’s early distribution. However, the data for early times typically has substantial limitations. Finding a single cluster with geographical outliers in the documentary evidence for a surname20 would be consistent with a single origin hypothesis. A single origin, followed by population growth and ‘normal migration’ for a populous single family, can be expected to lead, most often, to a cluster around the family’s early location. Such a geographical cluster can be accompanied by other instances of this family’s name that are more widely spread. 

That can be because either, a particular male has migrated far; or, several progressive migrations have taken some fathers far after several generations. However, finding a single cluster does not prove that the surname had just one origin. Such a deduction would involve assuming that there is no missing, early data for other origins elsewhere; and, that everyone in the geographic cluster belongs to just one family. Instead of a single origin, the surname could have had plural origins, which then rarefied or coalesced into the semblance of a single cluster. Such can be the limitations of the available documentary evidence, which is usually patchy for a surname’s early times in some geographical regions more than others. As a slightly more complex case, one might consider two, statistically significant clusters being found for the early distribution of a surname. That might represent two distinct origins. However, there remains some uncertainty in that the second cluster might have arisen from an individual who migrated far, at an early stage when the family’s population was few.21（essay代写)

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