Loss of ancestry

Charles II of Spain (1661–1700): Due to the loss of ancestors, his 5th generation of ancestors counted only 10 different people instead of the possible 32. Of his 8 great-grandparents, 6 were descended directly from Johanna der Wahnsinnigen (1479–1555).

Ancestral loss (also ancestral loss or implex ) describes in genealogy the difference between the possible total number of ancestors (ancestors) of a person and the actual number. Ancestors are lost when relatives have children with one another, for example through cousin marriage , and one and the same person therefore has two positions in the ancestral list . Examples of severe ancestral loss can be found in populations that have been isolated for a long time , such as island dwellers, religious minorities or high nobility .

Explanation

Pedigree of Charles II

Like all living things with bisexual reproduction , humans have two biological parents. Each parent also had two parents, and so on. The maximum possible number of ancestors of a person in the nth previous generation is , for example, for the great-grandparents (third previous generation): = 2 × 2 × 2 = 8 different great-grandparents' parts (see also the Kekule numbers of the generation names ). In addition, there are ( - 2) ancestors in the generations in between (here: 2 parents + 4 grandparents' parts, together - 2 = 6 ancestors). Ancestors are lost when relatives have children together. The descendants then have fewer ancestors than the maximum possible number (see also cousin marriage , relatives marriage ). If the parents of a person were first cousins, their own children have an ancestral loss of around 25%, as they already have six ancestors in their ancestral generation of the grandparents instead of eight different ancestors: two grandparents are always identical because they are the parents are from a pair of siblings . This decrease (loss) continues in all previous generations. ${\ displaystyle 2 ^ {n}}$ ${\ displaystyle 2 ^ {3}}$ ${\ displaystyle 2 ^ {n}}$ ${\ displaystyle 2 ^ {3}}$

In the case of sibling marriage, ancestors are already lost in the second generation , since the test person has not four, but only two grandparents. Since most human societies have a taboo on incest , ancestral loss usually occurs in the third generation at the earliest, but usually only in later generations. In these cases, siblings appear as ancestors, so that in the next generation their parents appear several times as ancestors. It can also happen that a person appears as an ancestor in different generations. This reduces the number of actually different ancestors compared to the number of theoretically possible ancestors, from which the inbreeding coefficient of the ancestral list can be estimated.

Example: Up to the third generation a person has 14 ancestors (2 parents , 4 grandparents and 8 great-grandparents ) - if there had been a cousin marriage between them with offspring, one of them would occupy two positions in the ancestor list , so that only 13 distinguishable ancestors remained.

If one looks at long generations of succession and also thinks of the ancestral community of mankind , ancestral loss is a natural and unavoidable process. If you put a generation at 25 years of age, then the year 1000 AD is about 40 generations ago. A modern person would theoretically have 2 ⁴⁰ ancestors in the 40th previous generation , that is over a trillion people (the 1st to 39th previous generations put together about another trillion ancestors). So many people didn't even live back then.

Ancestral loss can also play a role in animal breeding , for example the so-called ancestral loss coefficient of an individual is calculated in dog breeding .

Loss of ancestors with different degrees of relationship

The greatest possible reduction in ancestry has a person whose parents are descended from one another , one of whom is the child or grandson of the other (see also prohibition of incest ). For example, if a father conceives a child with his ( biological ) daughter , the paternal and maternal relationships completely overlap for this child : the paternal grandfather (father of the father) is also the maternal great-grandfather (mother's grandfather) who is the paternal grandmother at the same time the maternal great-grandmother; four ancestral positions are occupied by only two ancestors, and so on. In addition, his father is also his grandfather (since his mother's father), his grandfather is also his great-grandfather , and so on in ascending order.

A person whose parents are full brother and sister has a 50 percent ancestral loss (see also sibling marriage): The father and mother relatives are congruent because their parents have the same mother and father. Since all ancestors of the person occupy two positions in their list of ancestors at the same time, the total number of their actual ancestors is halved - the complete kinship tree of a parent who is not related to the other is missing. The ancestral loss here coincides with the relationship coefficient of full siblings: 0.5 = 50%.

The third largest loss of ancestors is caused by the descendants of the uncle - niece or nephew-aunt connection (example: uncle-niece marriages in the Bible ); it is roughly equivalent to the ancestral loss of descendants from a union of half-siblings or a grandparent with his grandchild .

Examples

High nobility

Since the ancestors of nobles are particularly well documented and published and marriages between close relatives were particularly frequent for reasons of equality and inheritance law, most examples in the literature refer to members of European ruling families .

A prime example of ancestral loss is Alfonso XII. of Spain, whose grandfathers were brothers and whose grandmothers were sisters. As a result, he only has 4 great-grandparents (instead of 8), as both pairs of great-grandparents appear on both the paternal and the maternal side. Thus, his parents Francisco de Asís de Borbón and Isabella II only have 4 grandparents together and thus have a gene pool that is normally only found in siblings. The loss of ancestors is compounded by the fact that the two grandmothers Luisa Carlota of Naples-Sicily and Maria Christina of Naples-Sicily are also the nieces of their husbands Francisco de Paula de Borbón and Ferdinand VII of Spain (i.e. the two grandfathers of Alfonso XII). ) were, with the result that Charles IV of Spain and his wife Maria Luise von Bourbon-Parma were both great-grandparents and great-great-grandparents of Alfonso XII. were on both the paternal and maternal side.

Another particularly clear example of ancestral loss in the high nobility is Charles II of Spain, all of whose great-grandparents (sometimes several times ) descended from Johanna von Kastilien (Johanna der Wahnsinnigen), although he only had 6 great-grandparents, as the "missing" 2 great-grandparents were already Grandparents appear in his pedigree. In the 5th generation (great, great, great-grandparents) there are only 10 new people, the remaining 22 (of a total of 32 possible) are already in the 4th generation or appear several times in the 5th generation.

For Frederick the Great , Maria Theresa and August the Strong , the loss of ancestors can be determined in absolute terms and in percent over 12 generations (based on the publications of Erich Brandenburg 1934–1937). And even with today's members of the high nobility such as the Spanish King Felipe or King Harald V of Norway , the ancestral decline can be clearly seen:

Ancestors - generation	1.	2.	3.	4th	5.	6th	7th	8th.	9.	10.	11.	12.
Theoretical ancestry	2	4th	8th	16	32	64	128	256	512	1024	2048	4096
Actual number of ancestors
Frederick the Great	2	4th	6th	10	18th	35	63	118	201	357	627	1108
Loss of ancestry	00%	00%	25%	38%	44%	45%	51%	54%	61%	65%	69%	73%
Maria Theresa	2	4th	8th	16	26th	50	74	113	158	238	351	569
Loss of ancestry	00%	00%	00%	00%	19%	22%	42%	56%	69%	77%	83%	87%
August the Strong	2	4th	8th	14th	23	39	52	74	122	196	302	499
Loss of ancestry	00%	00%	00%	13%	28%	39%	59%	71%	76%	81%	85%	88%
Charles II of Spain	2	4th	6th	10	10	18th	32	55	88
Loss of ancestry ( graphic above )	00%	00%	25%	38%	69%	72%	75%	79%	83%
Alfonso XII from Spain	2	4th	4th	6th	8th	16	28	48	70
Loss of ancestry	00%	00%	50%	63%	75%	75%	78%	81%	86%
Felipe VI. from Spain	2	4th	8th	16	26th	42	55	79	132
Loss of ancestry	00%	00%	00%	00%	19%	34%	57%	69%	74%
Harald V of Norway	2	4th	6th	10	18th	34	57	92
Loss of ancestry	00%	00%	25%	38%	44%	47%	56%	64%
Jean of Nassau	2	4th	6th	12	24	44	64	112	188
Loss of ancestry	00%	00%	25%	25%	25%	31%	50%	56%	63%
Henri of Nassau	2	4th	8th	14th	25th	46	81	123	204
Loss of ancestry	00%	00%	00%	12%	22%	28%	37%	52%	60%
Theoretical ancestry	2	4th	8th	16	32	64	128	256	512	1024	2048	4096
Ancestors - generation	1.	2.	3.	4th	5.	6th	7th	8th.	9.	10.	11.	12.

Charlemagne as the ancestor of all living Europeans

To illustrate the loss of ancestors, one often finds (especially in Internet forums) the assertion that this would also mean that “statistically speaking, all Europeans living today must descend from Emperor Charlemagne and thus every European would have noble ancestors (whether over the legitimate or illegitimate line) ”or - in the English-speaking world -“ that all British descend from King Edward I (or optionally Alfred the Great ) ”.

It is easy to calculate that each person has a maximum of 2 ⁿ ancestors (i.e. without losing ancestors) n generations ago. 30 generations ago this would be 2 ³⁰ , i.e. over a billion ancestors. This is significantly more than the entire world population around 750 years ago, so that mathematical proof is provided that every person must be affected by an implex within this period of time. Claims that every person must descend from a certain person before this time are not based on statistics , but on the erroneous assumption that the forefathers were evenly distributed among the people living at the time. However, this would mean that the test person would just as often be descended from Charlemagne as from a childless contemporary of Charlemagne, which is obviously not the case.

Simplified calculation models lead to quantitative statements , which force a certain statistical distribution (here a Poisson distribution ) through a series of assumptions, for example:

a homogeneous mix of populations (the fishmonger from Hamburg marries the Bavarian dairymaid; the Franconian noblewoman marries a blacksmith from Württemberg; in Breslau a Catholic citizen marries a Jewish citizen)
a homogeneously growing population (no immigration, equal chances of survival for all)

However, these models do not represent reality well. Further explanations on this aspect of the loss of ancestry can be found in the specialist literature.

Mitochondrial Eve

A new approach to the subject of ancestral loss is provided by genetic studies that have been developed since around 1990 under the topic of mitochondrial Eve . These data suggest that all people living today are descended from a single woman and are therefore all blood related to one another (see also Adam on the Y chromosome ).

Ancestry loss versus inbreeding

In dog breeding in particular , the so-called ancestral loss coefficient (AVK) is occasionally used as a measure of the inbreeding of an individual . To do this, one calculates the quotient of existing ( ) and maximum possible ancestors ( ) over a defined number of generations . The difference between the result and 1 (or 100%) corresponds to the value sought. ${\ displaystyle A_ {v}}$ ${\ displaystyle A_ {m}}$

${\ displaystyle AVK = 1 - {\ frac {A_ {v}} {A_ {m}}}}$

In contrast to the inbreeding coefficient , the ancestor loss coefficient does not take into account how closely sire and dam are related to each other (see kinship coefficient ). In the case of inbred, but not closely related parent animals, this can lead to the offspring having a high ancestor loss but at the same time a low inbreeding coefficient.

Since the degree of inbreeding depression himself behind the homozygosity directed -degree, which in turn is measured by the inbreeding coefficient, in such cases, the inbreeding coefficient is to be attached more importance than the ancestor loss. The ancestral loss coefficient provides at best an estimate, at worst, however, completely meaningless information on true inbreeding. It is therefore not used in scientific genetics .

literature

Eckart Henning , Wolfgang Ribbe (Hrsg.): Handbuch der Genealogie. Degener, Neustadt / Aisch 1972.
Hermann Athens: Theoretical Genealogy. In: Sven Tito Achen (Ed.): Genealogica & Heraldica: Report of the 14th International Congress of Genealogical and Heraldic Sciences in Copenhagen 25. – 29. Aug. 1980. Copenhagen 1982, pp. 421-432 (English).
Ahasver von Brandt : The people: Genealogy. In: The same: Tool of the historian: An introduction to the historical auxiliary sciences. 17th edition. Kohlhammer, Stuttgart 2007, ISBN 978-3-17-019413-7 , chapter 2.3., Pp. 39–47, here p. 42 (11th supplemented edition 1986, first edition 1958; page preview in the Google book search).

Web links

Arndt Richter: Selection of literature on the subject of "Loss of ancestors" (Implex). In: GeneTalogie. Own website, April 26, 2015.

Individual evidence

↑ It should also be mentioned that the paternity of Francisco de Asís de Borbón is controversial, see Ancestors of Alfonso XII .
↑ Compare Peter Chr. Clemens: Family Research and Mecklenburg - Diverse Aspects. (No longer available online.) In: uni-rostock.de. Association for Mecklenburg Family and Personal History e. V., January 24, 2004, archived from the original on August 27, 2009 ; accessed on March 12, 2020 .
↑ Compare Richard Dawkins : Stories from the Origin of Life. A journey through time in Darwin's footsteps , Ullstein, Berlin 2008, ISBN 978-3-550-08748-6 (original 2004: The Ancestor's Tale. A Pilgrimage to the Dawn of Evolution ).

[Alfons_XII-1] It should also be mentioned that the paternity of Francisco de Asís de Borbón is controversial, see Ancestors of Alfonso XII .

[Clemens_2004-2] Compare Peter Chr. Clemens: Family Research and Mecklenburg - Diverse Aspects. (No longer available online.) In: uni-rostock.de. Association for Mecklenburg Family and Personal History e. V., January 24, 2004, archived from the original on August 27, 2009 ; accessed on March 12, 2020 .

[Dawkins_2004-3] Compare Richard Dawkins : Stories from the Origin of Life. A journey through time in Darwin's footsteps , Ullstein, Berlin 2008, ISBN 978-3-550-08748-6 (original 2004: The Ancestor's Tale. A Pilgrimage to the Dawn of Evolution ).