Animal societies vary markedly in reproductive skew, the extent to which br
eeding is monopolised by dominant individuals. In the last few years, a lar
ge number of different models have been developed to explain this variation
. Here, I review existing models of reproductive skew, distinguishing betwe
en two basic types. Transactional models focus on group stability and the c
onstraints this places on the division of reproduction. Compromise models,
by contrast, ignore issues of group stability and view the division of repr
oduction as the outcome of a conflict in which each group member has a limi
ted or partial ability to enforce its own optimum. I go on to show, however
, that the division between transactional and compromise models is somewhat
artificial, and that both approaches may be combined in a single, syntheti
c treatment. Different models of reproductive skew are thus better seen as
special cases of a general underlying theory, rather than alternative parad
igms. I conclude with a brief discussion of the possibilities and problems
of empirically testing this unified theory of skew, and the prospects for f
uture theoretical advances.