2.1.2 | Admixture-pulse(s) scenarios
For a given source population S, African or European, scenariosS-2P consider two possible pulses of admixture into population H
occurring respectively at time t S,p1 andt S,p2 distributed in [1,20] witht S,p1 ≠ t S,p2, with
associated admixture proportion s S,tS,p1 ands S,tS,p2 in [0,1] satisfying, at all timest ,\(\sum_{S\in\left(Afr,Eur\right)}s_{S,t}\mathrm{\leq 1}\)(Figure 1 , Table 1 ). Note that for one of eithers S,t values close to 0, the two-pulse scenarios
are equivalent to single pulse scenarios after the founding of H.
Furthermore, for both s S,t values close to 0,
scenarios S-2P are nested with scenarios where only the founding
admixture pulse 21 generations ago is the source of genetic admixture.
Alternatively, s S,t parameter values close to 1
consider a virtual complete replacement of population H by population S
at that time, thus obliterating all previous admixture event.