  In 1960s V.Geodakian proposed a theory that explains sexes as a mechanism for
evolutionary adaptation of the species to changing environmental conditions. In
2001 V.Iskrin refined and augmented the concepts of Geodakian and gave a new
and interesting explanation to several phenomena which involve sex, and sex
ratio, including the war-years phenomena. He also introduced a new concept of
the "catastrophic sex ratio." This note is an attempt to digest technical
aspects of the new ideas by Iskrin.
