SUPPLEMENT TO GENETIC AND QUANTITATIVE ASPECTS OF GENEALOGY

BY F. M. LANCASTER

SEPTEMBER 2006

The main purpose of the following supplement is to anticipate and answer those questions most frequently asked about the genetic and quantitative aspects of genealogy and relationships. A secondary aim is to enlarge on certain specialised topics, which were only briefly covered in the monograph, but which may be of further interest. The following sections, which are summarised in the introduction below, give more information in both these areas. However, I would like to stress that my specialist subject is genetics and that any complicated enquiries related to marriage laws and intestate wills should be addressed to a qualified legal expert.

Contents

GENETIC AND QUANTITATIVE ASPECTS OF GENEALOGY This monograph is mainly concerned with the classification, graphic representation, measurement and coding of human relationships. It also explains the significance and harmful consequences of inbreeding. Other aspects of genealogy included are: generation intervals, legal constraints on the marriage of relatives and present rules for the inheritance of property.

ABOUT THE AUTHOR

CONTACT THE AUTHOR

Introduction

Acceptable and non-acceptable levels of inbreeding

The effects of inbreeding on the children of cousin marriages

Removed Cousins

Longevity and generation intervals

The ancestor paradox

The direct relationship paradox

Calculation of the coefficient of relationship (R) for sex-linked genes

Calculation of the coefficient of inbreeding (F) for sex-linked genes

Case histories of intestate wills

Extension of coding for relationships

Calculating the coefficient of inbreeding by coancestry

Examples of unusual relationships and genealogical rarities

References

List of Tables

Table 1 Acceptable and non-acceptable levels of inbreeding in human populations

Table 2 Coefficients of relationship between various degrees of cousins

Table 3 Proportion of homozygous recessive individuals in children from cousin marriages compared with those expected in a random-mating population, for different gene frequencies

Table 4 The effect of a first cousin marriage on the probability that the first great-grandson of an albino will inherit the same condition

Table 5 Removed cousins and other intergeneration collateral relationships

Table 6 Coefficients of relationship when all the genes are either sex-linked or autosomal

Table 7 F values of female progeny for sex-linked genes

Table 8 Incidence of sex-linked colour blindness

Table 9 Incidence of haemophilia

Table 10 Coding for non-reciprocal intergeneration doubles (regular)

Table 11 Coding for non-reciprocal intergeneration doubles (irregular)

Table 12 Coding for enhanced half sib doubles(all irregular)

Table 13 Coding for reciprocal cross - gneration double relatives

Table 14 Coding for double relationships caused by inbreeding

List of Figures

Figure 1 Four generation pedigree

Figure 2 Five generation pedigree

Figure 3 Six generation pedigree

Figure 4 Diagram showing loss of ancestors caused by a first cousin marriage

Figure 5 Broken male line

Figure 6 Y chromosome and mitochondrial inheritance

Figure 7 Parent and child relationships for sex-linked genes

Figure 8 Full sib relationships for sex-linked genes

Figure 9 Paternal half sib relationships for sex-linked genes

Figure 10 Maternal half sib relationships for sex-linked genes

Figure 11 Paternal uncle and aunt relationships for sex-linked genes

Figure 12 Maternal uncle and aunt relationships for sex-linked genes

Figure 13 Patrilateral ortho-cousins

Figure 14 Matrilateral ortho-cousins

Figure 15 Patrilateral cross-cousins

Figure 16 Matrilateral cross-cousins

Figure 17 First and second cousins

Figure 18 Basic Formula

Figure 19 Modified diagram for full sibs

Figure 20 Modified diagram for half sibs

Figure 21 First cousin marriages

Figure 22 Uncle-niece marriages

Figure 23 Double first cousin marriage

Figure 24 Close inbreeding (full sibs)