 My research is concerned with populations, local populations affected by mass violence in the context of genocide. The specific case that I am considering for my research are mass killings committed against the Maya Achi people in Guatemala. These events happened in the 1980s within a couple of months. One third of the population that I am studying, which is the population of Rio Negro, was massacred by militias supported by the military government of the time. In the context of the Guatemalan civil war, which took place between 1960 and 1996, specifically as a demographer, I am interested in the mortality and the fertility of populations, which are two of the main components of population change. My research asks how these violent events, how the mass killings against the Maya Achi people, affected the fertility and mortality outcomes in the short and in the long term for those that survived the killings. Studying the consequences of armed conflict on individuals is very difficult. In demography and in social science in general, because of the simple fact that armed conflicts generally result in a total breakdown of the data collection systems, on which we rely as researchers. So it can be that during an armed conflict, the statistical offices stop reporting births, stop reporting deaths. Surveys are no longer conducted because it's very difficult to access certain areas. In my particular case, where I was interested in understanding what the long term consequences of exposure to mass violence to massacres were. This is a particular challenge because we need data on the same population before the violence, during the violence and after the violence, and this type of information practically doesn't exist. For this reason, I developed a method called the extended genealogy method. The basic intuition of this method is that we can rely on the social networks around individuals to reconstruct historical information about them and their relatives. As humans, we are all embedded in networks that we call families or kinship. So we have all these kinship ties going to our parents or siblings, which means that even if one person dies, there are other people who are connected to this person who can give information about them. Our method basically reconstructs genealogies or family histories from survivors of the violence and collects data on them and on their relatives, even if they had already been killed. We conducted interviews for one year in the field in Guatemala, in the region of Rabinal, and we were able to reconstruct the entire population of Rio Negro in the last 60 years. With this information, since it includes the dates of birth, dates of death, dates of marriage and we know who is related to whom, it is possible to conduct high quality demographic analysis using statistical techniques from the social sciences to comprehend what the consequences of the mass killings were for those who were living in the area when the killings were committed. My key findings are related to the consequences of the mass killings in the short and the long term and also I discuss the mechanisms that drove these results. In the short term, the consequences of the killings are related to the mortality. So people were killed and I was interested in knowing who was killed and if particular sectors of society were more likely to be killed than others. What I found was that the distribution of mortality across age and sex was quite even, which means that children were almost as likely to die as adults and women were also almost as likely to die as men. This is surprising because we know that in armed conflicts, mortality is generally concentrated in young men who are of fighting age. So the fact that the mortality was even distributed across age and sex implies some degree of intentionality with regards to targeting the population as a whole and not a particular group such as young men. In the long term I was interested in the consequences of the killings on mortality and fertility for survivors. And the way I approached this was by comparing the groups of individuals depending on their exposure to the conflict. Basically, I was counting the number of relatives that were killed during the war and comparing those who lost more relatives to those who lost fewer relatives in the killings. I find that those who lost more relatives were more likely to die earlier after the conflict, showing that there is the consequences of the conflict go on linger over time. And this was particularly true for men. In terms of fertility, I find that a higher exposure to the conflict was actually associated with lower levels of fertility for women that survived the killing. I was also interested in the mechanisms that drove these processes. And apart from some mechanisms which are already known that can bring about this type of outcome such as the psychological effects, trauma, the physical consequences of being exposed to violence, I also identified a phenomenon that I call social scaring, which basically results when these networks or this social fabric in which an individual is embedded in society is disrupted by the violence. And because I had these social networks around individuals, I found that those who were more exposed to the violence also lost more social contacts around them. Contacts that provide basic and elemental support, particularly for children in the terms of transfers of care. So those who lost that kind of support were more vulnerable in the long term. My research contributes to demographic theory, methodology and to our understanding of history. Demographers have historically been very concerned with the interaction between changes in mortality and changes in fertility. And this has been studied in a variety of settings, but not so much in the context of armed conflict and never in the setting of genocide for local populations. My study follows the same population over time and considers how they were affected by mass killings. This provides valuable insights to our understanding of demographic dynamics in general, which can be later generalized to other populations and other settings. Methodologically, my research provides a new way of collecting data, of analyzing it, and I propose an approach to conceptualize the consequences of these mortality shocks. And as a matter of fact, my methodology can be applied to other settings. In terms of the contribution to history, this is the first study that systematically considers the consequences of the mass killings for the Maya Echee people, including quantitative analysis that allows us to get a sense of the dimension of this tragic event. I am now working to develop this methodology that I developed for this initial study and applying it not to small populations, but to big data from the internet. Using online genealogies, which have been crowdsourced by thousands of users online, it is possible to use methods from computational demography to understand demographic processes at a large scale. This allows us to study not only larger populations, but also considerably longer time frames. Hundreds of years in which we can study the consequences of demographic events, such as mortality shocks, not only over one, but over multiple generations.