The Balkan region is in a state of instability in the aftermath of Kosovo's independence, vulnerable to both inter- and intra-ethnic conflicts. Native Muslim populations in the Balkans continue to grow much more rapidly than non-Muslims. This paper attempts to assess maternal descendant-leaving success in 120 Muslim and Christian Orthodox women born between 1880 and 1924 in the Serbian multiethnic region of Sandzak. Differential fertility among ethnic groups is linked to the differences in religious affiliation. The paper will try to answer questions about the impacts of particular political and economic conditions on reproductive and lineage success for the two populations.Key Words: Balkans; Differential reproduction; Muslims; Christians; Sandzak; Serbia.Worldwide, religiosity-fertility links are a near-universal characteristic of today's cultures (Kaufmann 2008). In particular, individuals inclining to dogmatic and traditional religious beliefs out-reproduce those with more secular worldviews. Differential fertility among ethnic groups is linked to the differences in religious affiliation (Cvorovic 2012). Demography appears to be important for the historical rise and decline of religions because more than most other cultural traits, religion is transmitted within families (Steadman and Palmer 2008). The ability of traditional religious beliefs, values and behaviors to be repeatedly transmitted from ancestors to descendants enables them to influence the descendant-leaving success of individuals over many generations (Steadman and Palmer 1997). For instance, recent demographic reports indicate that native Muslim populations in the Balkans continue to grow much more rapidly than non-Muslims (Kettani 2010).An application of evolutionary theory to demographic data and human life history offers insights not only into the past, but also into modern problems, both large scale and urgent (Clarke and Low 2001, Wilson 1999). This paper attempts to assess maternal descendant leaving success of 120 women (52 Muslims and 68 Christian Orthodox) born between 1880 and 1924 in the Serbian southern region of Sandzak. Sandzak is a multi-ethnic region, a largely mountainous border area between Serbia and Montenegro, bordering Kosovo to the south-east and Bosnia and Herzegovina to the west, containing the largest concentration of Serbian Muslims, recognized as Bosniacs. At present, as in the past, Sandzak remains vulnerable to both inter- and intra-ethnic conflicts. Re-affirmations of national identity and presence by Christian Orthodox Serb and Muslim-Bosniac ethnic groups, mainly with respect to religion and language, threaten to prompt future resentment. In fact, the Balkan region is in a state of instability in the aftermath of Kosovo's independence, and thus areas of potential flux such as the Sandzak should be monitored closely (Morrison 2008:1).Vanhanen (1999) argued that ethnic conflict may appear by the mere existence of ethnic diversity, regardless of governmental style or policies. For instance, in the former Yugoslavia, ethnic competition and subsequent violence marked the past. In a multi-ethnic society, competition may include warfare between different ethnic groups over territory. Control of territory traditionally facilitated reproduction and development of cultural and economic traditions, hence the benefit of ethnic control is obvious - it aids a particular group to carry on its genes and traditions into subsequent generations (Cvorovic 2004). The problem of changing composition of the population along ethnic and regional lines was crucial in the Balkan crisis (Apostolov 2010).In the Yugoslav federation, built after the Second World War, ethnic conflicts were suppressed by the communist dictatorship. However, the federal state establishment also created the conditions for separation of the neighboring ethnic groups and creation of new ethnic identities which, along with changing population growth rates, inevitably led to conflict. …