The conquests of the first century of Islam gave the Arabian tribes access to tens of thousands of captured individuals. Those individuals who were enslaved could find themselves at the heart of the conquest society – none more so than the concubine, or umm walad. Thanks in part to the Islamic practice of children inheriting the legal status of the father, the offspring of these unions soon appeared in every political and religious context; as imams, qadis, governors and caliphs. While these male progeny are often preserved within the historical tradition, their mothers nearly always remain anonymous – in the vast majority of cases we know neither her name nor her place of origin. The approach taken in this paper will provide some context to these women. It will be shown that the richness of the Arab genealogical literary tradition of the 9th century (predominantly the Nasab Quraysh of al-Zubayri and the Jamharat al-Nasab of Ibn al-Kalbi) provides us with the resources to create a database of nearly 3,000 Qurashi individuals for whom we know the status of the mother. By applying statistical and prosopographical methods to this database we can uncover trends indicating changes in the number of umm walads over time, and variations in the ratios of children born to umm walads according to tribal grouping. These trends can then be linked to information preserved in other historical sources to show that a statistically-indicated prejudice against having children by concubines has parallels in outside references. This trend data on concubine unions is an invaluable tool in other types of analysis; accounting for the umm walads (who are completely outside the Arab tribal system) means that we can turn to marriage activity within the tribes to investigate links between endogamous or exogamous behaviour and political or religious affiliations. Finally, it will also be shown that the statistical analysis of the database can provide historiographical insights into the Arab genealogical literary tradition – a tradition which is in many ways unique to Islam.