Allele-sharing asymmetry and alternative histories
Research context
research method · established · As of 2026-10-10
The D statistic compares two discordant allele-sharing patterns in an ordered four-sample test.
Key knowledge
The D statistic compares two discordant allele-sharing patterns in an ordered four-sample test. Nonzero asymmetry can support gene flow under the null model, but ancestral subdivision and differential sequencing error can produce competing explanations.
Values and equations
D = (n_ABBA - n_BABA)/(n_ABBA + n_BABA)
- D
- normalized allele-sharing asymmetry in order P1,P2,P3,O 1
- n_ABBA
- informative sites where P2/P3 share the derived allele 1
- n_BABA
- informative sites where P1/P3 share the derived allele 1
Conditions and scope
- Specify topology ((P1,P2),P3), outgroup O, ancestral mating and ascertainment assumptions; linked sites require appropriate uncertainty estimation. The displayed D requires n_ABBA + n_BABA > 0; it is undefined with no informative patterns.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Testing for Ancient Admixture between Closely Related Populations: Equation (1), ancestral-subdivision model and discussion of sequencing errors/identifiability (extracted original full-text sections)
2026-10-10 · Bounded author source inspection of allele-sharing asymmetry and alternative histories, including the stated conditions; independent branch review is recorded separately.
Entry details
Permanent link to this entry ↗- Record identity
- res-bio-admixture-discrimination
- Revision
- research.1
- Structured reference record
- Postgraduate & research reference