Here is a quotation from this wikipedia page

The relatedness parameter (r) in Hamilton's rule was introduced in 1922 by Sewall Wright as a coefficient of relationship that gives the probability that at a random locus, the alleles there will be identical by descent.[14] Subsequent authors, including Hamilton, sometimes reformulate this with a regression, which, unlike probabilities, can be negative.

Here is my question:

  • What are all the different definitions of relatedness in biology?
    • how do we calculate them?
    • what do they mean?
  • $\begingroup$ You should break this up into several questions - too many questions rolled into one at the moment, and single answers will probably not cover all of them. $\endgroup$ Oct 25, 2013 at 16:35
  • $\begingroup$ @fileunderwater I updated the post. Thanks for your comment. $\endgroup$
    – Remi.b
    Oct 25, 2013 at 16:42

1 Answer 1


Is that really trying to imply that there are significantly different definitions? It seems to me the intent was just to put it in terms of an equation with more useful numbers. This terrifying paper from 1964 gives some of the follow-up works, in particular works from Cockerham in 1954 and a number of papers by Kempthorne, in particular this from 1955 and this from 1963. There is also Malecot's method of coancestry from 1948. (WorldCat.org link) The idea was mainly to look relatedness outside of the specific limitations present in Wright's work. Some of the math in those are more accessible than others...


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