GENETIC AND QUANTITATIVE ASPECTS OF GENEALOGY

BY F. M. LANCASTER

OCTOBER 2005 (Updated November 2007)

The following 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.

Contents

SUPPLEMENT TO GENETIC AND QUANTITATIVE ASPECTS OF GENEALOGY

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.

ABOUT THE AUTHOR

CONTACT THE AUTHOR

INTRODUCTION

SCOPE AND LIMITS FOR THE COLLECTION OF DATA

GRAPHIC REPRESENTATION OF RELATIONSHIPS AND FAMILY TREES

CALCULATION OF THE COEFFICIENT OF RELATIONSHIP

CLASSIFICATION OF RELATIONSHIPS

PATTERNS OF DIRECT RELATIONSHIP

TYPES OF COLLATERAL RELATIONSHIPS

IDENTIFICATION OF COLLATERAL RELATIONSHIPS ACROSS GENERATIONS

CHANGING PATTERNS OF RELATIONSHIP

CODING OF RELATIONSHIPS

GENERATION INTERVALS AND THEIR SIGNIFICANCE

INBREEDING AND ITS CONSEQUENCES

THE COEFFICIENT OF INBREEDING (F) AND ITS APPLICATIONS

FORBIDDEN MARRIAGE LAWS OF THE UNITED KINGDOM

INHERITANCE LAWS OF THE UNITED KINGDOM

List of Appendices

Appendix A- EXTENDED FORMULAE FOR THE COEFFICIENT OF RELATIONSHIP

Appendix B - ACCURACY AND RELIABILITY OF THE COEFFICIENT OF RELATIONSHIP

Appendix C - CROSS-COUSINS AND ORTHO-COUSINS

Appendix D - TWIN AND MULTIPLE BIRTH FREQUENCIES

Appendix E - INHERITANCE OF SEX-LINKED COLOUR BLINDNESS

Appendix F - CONVENTIONS AND ABBREVIATIONS

REFERENCES

ACKNOWLEDGEMENT

ADDENDUM - The Geometric Mean

GLOSSARY

List Of Figures

Figure 1 Family Tree Diagrams

Figure 2 Path Diagram

Figure 3 Genetic History Diagram

Figure 4 Sex-linked Colour Blindness (Stern, 1960)

Figure 5 Great Dane Pedigree

Figure 6 Path Diagram of the Pedigree in Figure 5

Figure 7 Common Ancestors

Figure 8 Direct Relationship Calculation

Figure 9 Marriage between Second Cousins (K and L)

Figure 10 The Relationship between Single First Cousins

Figure 11 Two Brothers (I and J) whose Parents are First Cousins

Figure 12 Combined Relationships

Figure 13 Relationship between Identical Twins

Figure 14 Identical Twin Common Ancestors

Figure 15 Direct Relationships

Figure 16 Collateral Relationships

Figure 17 First Cousin Marriage

Figure 18 Unililineal Relationships

Figure 19 Bilineal Relationships

Figure 20 Single versus Double Relationships

Figure 21 A Regular Double Relationship (Double Half First Cousins)

Figure 22 An Irregular Double Relationship

Figure 23 Sib Relationships

Figure 24 Identical Twin Mothers

Figure 25 Half Sib Mothers

Figure 26 First Cousins

Figure 27 Second Cousins

Figure 28 Third Cousins

Figure 29 Once Removed

Figure 30 Twice Removed

Figure 31 Uncle/Aunt - Nephew/Niece Relationships

Figure 32 Regular Double First Cousins

Figure 33 Regular Double Second Cousins

Figure 34 Irregular Double Cousins

Figure 35 Father and Son - Daughter and Mother Reciprocal Marriages

Figure 36 Uncle and Nephew - Niece and Aunt Reciprocal Marriages

Figure 37 Father and Son - Niece and Aunt Reciprocal Marriages

Figure 38 Father and Son - Half Niece and Half Aunt Reciprocal Marriages

Figure 39 Double (Half Uncle/Half Aunt - Half Nephew/Half Niece)

Figure 40 Double (First Cousins Once Removed)

Figure 41 Double (Half First Cousins Once Removed)

Figure 42 Half Uncle - Half Nephew (R=1/8) and First Cousins (R=1/8)

Figure 43 Half Uncle - Half Nephew (R = 1/8) and First Cousins Once Removed (R = 1/16)

Figure 44 Half Uncle - Half Nephew (R = 1/8) and Half First Cousins (R = 1/16)

Figure 45 Half First Cousins Once Removed (R = 1/32) and First Cousins (R = 1/8)

Figure 46 Half First Cousins (R = 1/16) and First Cousins Once Removed (R = 1/16)

Figure 47 Half First Cousins Once Removed (R = 1/32) and First Cousins Once Removed (R = 1/16)

Figure 48 Half Aunt - Half Niece (R = 0.125) and Half Sibs (R = 0.25)

Figure 49 First Cousins Once Removed (R = 0.0625) and Half Sibs (R = 0.25)

Figure 50 Half First Cousins Once Removed (R = 0.03125) and Half Sibs (R = 0.25)

Figure 51 Conventional Double (First Cousins) Once Removed

Figure 52 Conventional Double (First Cousins) Twice Removed

Figure 53 Conventional Double (Second Cousins) Once Removed - Second Type

Figure 54 Irregular Double (First Cousins/Half First Cousins) Once Removed

Figure 55 Full Sibs who are also Double Second Cousins

Figure 56 Quadruple Second Cousins (QSC) and Octuple Third Cousins (OTC)

Figure 57 Triple Half First Cousins

Figure 58 Quadruple Half First Cousins

Figure 59 Octuple Half Second Cousins

Figure 60 Uncles/Aunts and Nephews/Nieces versus Removed Cousins

Figure 61 Coding for Removed Cousinships

Figure 62 Assignment of Generation Numbers

Figure 63 Indeterminate Generation Numbers

Figure 64 Example with Inbred Common Ancestor

Figure 65 Example without Inbred Common Ancestors

Figure 66 Close Inbreeding as used for Animals (3 generations of full sib mating)

Figure 67 Marriages between Sibs and Half-sibs in the 18th Dynasty of Egypt, c. 1580 - 1350 B.C.

Figure 68 Father-daughter Mating

Figure 69 Directly Related Parents Only

Figure 70 Directly and Collaterally Related Parents

Figure 71 Showing Degrees of Consanguinity of Various Relatives

Figure 72 Showing Degrees of Consanguinity Using Coded Relationships

Figure 73 Consanguinity Chart in Pedigree Form (males only)

Figure 74 The Order of Distribution for Intestate Estates in England and Wales

Figure 75 Showing Coefficients of Relationship Between the Deceased and Various Relatives

Figure 76 Pedigree Involving Three First Cousin Marriages

Figure 77 Pedigree Involving a Forbidden Uncle-niece Relationship

Figure 78 Father-daughter and Brother-sister

Figure 76 Sib Relationship Following Three Generations of Full Sib Mating

List Of Tables

Table 1 Values of (½)n

Table 2 Standard Relationship Values

Table 3 Enhancement through Identical Twins

Table 4 Enhanced Half Sib Relationships

Table 5 Common Types of Irregular Double Cousins

Table 6 Different Types of Reciprocal Cross - generation Double Relatives

Table 7 Non-reciprocal Intergeneration Doubles

Table 8 Single, Double and Multiple Half First Cousins

Table 9 Chart for Determining Collateral Relationships

Table 10 Relationships Across Generations

Table 11 DIRECT RELATIONSHIPS

Table 12 COLLATERAL RELATIONSHIPS

Table 13 UNUSUAL COLLATERAL RELATIONSHIPS a) Twins

Table 14 UNUSUAL COLLATERAL RELATIONSHIPS b) Regular Double Cousinships

Table 15 UNUSUAL COLLATERAL RELATIONSHIPS c) Irregular Double Cousinships

Table 16 Removed Relationships for Conventional Double Cousins a) Regular Double First Cousins (First Degree)

Table 17 Removed Relationships for Conventional Double Cousins b) Regular Double Second Cousins

Table 18 Removed Relationships for Conventional Double Cousins c) Irregular Double Cousins (1st Cousins / 2nd Cousins)

Table 19 Values of F for Consanguinous Matings (One generation, no previous inbreeding).

Table 20 Inbreeding Depression for Every 10% Increase in F

Table 21 Effects of Inbreeding on the Frequency of Inherited Defects

Table 22 List of Forbidden Marriages (1560 list)

Table 23 Simplified List of Forbidden Marriages (1560 list)

Table 24 List of Forbidden Marriages (1949 version)

Table 25 Simplified List of Forbidden Marriages (1949 version)

Table 26 In-laws Whom the Nominated Person Can Marry With the Above Restrictions (1949 Act)

Table 27 Simplified Version of Table 26

Table 28 Blood Relatives Forbidden to Marry

Table 29 Further In-laws Who Can Marry Without Restrictions

Table 30 Step-relatives Who Can Marry With the Above Restrictions

Table 31 In-laws Who Can Marry With the Above Restrictions

Table 32 Relatives by Adoption Who Are Forbidden to Marry

Table 33 Further Forbidden Marriages (Scotland)

Table 34 Expected Proportions of Genotypes with Colour Blindness

Table 35 Details of Six Mating Types