Talk:Coefficient of relationship

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Moved from main article[edit]

== Sexual organisms ==
 
=== Parent-offspring ===
 
For a sexual organism, the coefficient is 0.5.
 
== Haplodiploidy ==
 
In haplodiploidy, things get screwed around a bit.
 
== Philandering ==
 
being naughty reduces the coefficient.
 
== Sex chromosomes ==
 
Sex chromosomes reduce the relatedness slightly http://www.husdyr.kvl.dk/htm/kc/sexrelat.htm 
 
== Finite populations ==
 
Finite and small population size mean that it can be negative.  hence spite.

It was already commented out, so I put it somewhere more public. Anyone want to fix this? alerante  20:55, 9 September 2005 (UTC)

Wording updates needed[edit]

The article addresses the reader directly, for example by posing questions, which WP:TONE says is inappropriate tone for an article. Can someone take a crack at re-writing these sections to use a better tone? --ΨΦorg (talk) 22:27, 6 October 2008 (UTC)

Not numerology[edit]

Someone acting under the cover of a bare IP number categorized the article as "Numerology". I have reverted this as it isn't numerology, but describes a useful quantity that connects to scientific theories. Felsenst (talk) 12:01, 17 July 2010 (UTC)

Coefficients incorporating incestuous ancestry?[edit]

Has it been calculated what effect previous incestuous relationships in the parents' ancestries have?

E. g., how would 'r' increase for two first cousins where one is already the result of such relationship and the other has a parent who is also such a result? -- 91.14.188.5 (talk) 22:22, 6 October 2011 (UTC)

2 x the coefficient of inbreeding?[edit]

The coefficient of inbreeding of who? One individual? Perhaps you meant the coefficient of kinship of a random copy of the gene in one individual with a random copy of the gene in the other? Felsenst (talk) 12:28, 25 October 2011 (UTC)

The second sentence of the page is

The 'Coefficient of Relatedness' (or: coefficient of kinship) is defined as the probability that the alleles at a particular locus chosen at random from two individuals are identical by descent.

This is totally unclear. The coefficient of kinship between individuals A and B is the probability that a random one of the two copies from A is identical by descent to a random one of the two copies chosen from individual B. That is also the inbreeding coefficient of the offspring that would result from mating individual A and individual B. (Although we can calculate the coefficient of kinship even for two indviduals who cannot be mated, as when they are of the same sex). The coefficient of relationship used in (say) kin selection calculations is different. Felsenst (talk) 15:29, 26 October 2011 (UTC)

Well, the case is much more complicated than this article suggests. These coefficients were defined for use in actual breeding (of animals, I should say, even though they are now also used to examine human genealogies). Their definition is correspondingly complicated. To calculate the coefficient, you would need to know the complete family tree of the two individuals down to all of their common ancestors. This is usually the case in breeding situations, where you start with a given ancestor population and then keep accurate records of each pairing, but it is clearly impossible in most human scenarios. The point is that if the number of generations separating the two individuals from their common ancestors increases, the coefficient approaches zero.

So, the "dumbed down" definition of this coefficient is that you assume that all common ancestors except the ones under explicit consideration are assumed to be arbitrarily far removed. In this case, you get the simple powers-of-two rules of "siblings 2^-1, cousins 2^-3, second cousins 2^-5" etc. But obviously this article should give the full definition, and then treat the simplified "cousins table" as a special case. --dab (𒁳) 15:03, 5 January 2012 (UTC)


ok, I should admit that I am struggling here, as I am reading up on this definition for the first time. Help is appreciated. What is clear is that the article was completely mistaken. The coefficient isn't even defined in terms of genetics, but in terms of genealogy. It can be calculated precisely if the full genealogy is known, never mind genetics. Of course it is intended to still make a statement about genetic relatedness, but that's not part of its strict definition. It is intended to describe breeding processes of mammals, so I am not sure it can even be meaningfully applied to hymenoptera genealogies. I have so far looked up the 1922 definition of r. It involves summing over all paths in the full genealogy. The thing being summed are path coefficients, and these path coefficients are in turn defined in terms of the inbreeding coefficient. As the inbreeding coefficient isn't defined in the 1922 paper, the reader just being referred to the 1921 one, I have not so far been able to supply the full definition. --dab (𒁳) 15:30, 5 January 2012 (UTC)