“…A new population has been formed from two previously separated ones, and this population will have its own fitness value. Thus we can estimate the relative fitnesses of two populations and find, for example, that the relative fitness of population A is higher than that of population B, but this does not allow the prediction of the relative fitness of the new population formed from (A+ B) (see also Vetukhiv, 1953Vetukhiv, , 1954Wallace, King, Madden, Kaufmann, and McGunnigle, 1953;Brncic, 1954;Cordeiro and Dobzhansky, 1954;Spassky et al, 1958;Dobzhansky et al, 1959;and Spiess, 1959).…”