**5. Discussion**

The extensive survey of the archaeogenetic studies of Sicily since the Troina meeting presented in this paper verifies that many of the predictions and plans made at that meeting have been realized. Nevertheless, it is worth remembering that the reconstruction of the genetic history of the island is a growing field of investigation, and this survey of the published efforts clearly indicates that there are many difficulties that remain. This is somewhat inevitable, given that the analyses conducted thus far have only involved a small part, perhaps not even representative, of the extensive archaeological and historical evidence pertaining to the island, containing (by a previous outdated prediction) over 3000 registered sites. This contrast is better illustrated by comparing the map of archaeological sites surveyed to date (Figure 2) and the map of sites sampled for DNA analyses (Figure 3).

The new NGS technologies will undoubtedly have important effects. As a first step, it is necessary to increase the coverage of ancient genomes by focusing on the cultural and bio-demographic processes that have shaped the current genetic landscape. In our opinion, the extent of the genetic contribution made by Iron Age indigenous peoples is a highly debated issue that needs to be addressed (Figure 2e), as this contribution may have been masked by subsequent migration events.

Another fundamental area of focus will be forming a better understanding of the impact on the present-day Sicilian gene pool of Greek and Punic colonizations, beginning with the founding events of the eighth and the sixth centuries BCE (Figure 2g). The evaluation of the demographic dimension of colonization may be indirectly inferred through changes in vegetation cover recorded by paleoecological analyses. The movement of people and the effective genetic impact of their settlements is tied to ecological and environmental factors. The evaluation of the ecological and paleo-botanical characteristics of the territory is thus important, as this helps in reconstructing the diffusion and demographic repercussions of the different Holocene human flows.

In our opinion, it is necessary to proceed, with reinvigorated effort, with the integrated study of modern and ancient genomes, in order to achieve a completer and more accurate picture of the population history of Sicily. We would like to mention here the research project AGED "1000 Ancient Italian Genomes: Evidence from ancient biomolecules for unravelling past human population Dynamics", begun in 2020, which aims to study the dynamics of population that have characterized the Italian peninsula via a multidisciplinary approach based on the paleogenomic, isotopic, and radiometric analysis of ancient biological samples from the Paleolithic to Middle Age. As far Sicily is concerned, the AGED project aims to provide an interpretation of genetic data for Sicily via a detailed

examination of the population dynamics associated with the cultural, demographic, and environmental changes that took place during the prehistory and history of the island. In turn, the genetic, demographic, and cultural changes need to be understood in the context of the environmental changes that took place over the Holocene.

### **6. Concluding Remarks**

While, on one hand, the literature surveys on the three themes (ethnic/archeological, archeogenetics, past vegetation/landscape) discussed in this review were intended to offer the reader a systematic knowledge about the state of art of studies performed on various aspects of the prehistory, protohistory, and history of Sicily, on the other hand, we wish to sugges<sup>t</sup> here a few ideas for future studies on Sicily, hoping they will serve as a useful general theoretical framework. First of all, we underscore the importance of pursuing an interdisciplinary approach to gain a deeper understanding of the complex dynamics that have characterized the past timeline of Sicily. More specifically, we think that the most effective and appropriate way to implement such an interdisciplinary approach is to undertake a systems level analysis of Sicily by which to investigate the many crosstalk events that have occurred between the cultural and biological evolutions during the Holocene. Indeed, as it was extensively discussed in the landscape section of this review, the two types of evolution have interacted and influenced each other at different periods and places within the island. Moreover, we propose that such evolutionary changes would be better understood if they are considered in terms of the changes in biodiversity and sustainability of the Sicilian ecosystem. Here, the term biodiversity is used to include the genotypic as well as phenotypic changes of the humans, animals, and plants that have lived in the island throughout this time frame. From this perspective, changes of sustainability can be causally linked to changes in biodiversity of the Sicilian ecosystem. In turn, such changes need to be studied as a response to natural (e.g., climatic, geological) and cultural (e.g., transition from a hunter-gatherer to agricultural economy) influences. Within this framework, the contribution of archaeogenetic studies will help to reconstruct the dynamics of human populations. Throughout the Holocene, these dynamics have constituted the main driver of the prehistoric and historical changes of Mediterranean landscapes. Despite its long human history, the Mediterranean is still one of the world's biodiversity hotspots and Sicily is one of its important areas [95]. The lessons we learn from the past use of landscape provide models for the sustainable future managemen<sup>t</sup> of the Mediterranean's landscapes.

**Author Contributions:** Conceptualization, L.S., V.R. and G.B.; writing draft on ethnic and demographic dynamics, L.S. and G.C.; writing draft on archaeogenetics of Sicily, V.R., G.C. and F.C.; writing draft on past vegetation and landscape dynamics, G.B.; GIS analysis and mapping, G.B.; writing—review and editing, L.S., V.R., G.C., F.C. and G.B.; supervision, L.S.; funding acquisition, L.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work has been supported by the project "1000 Ancient Italian Genomes: Evidence from ancient biomolecules for unravelling past human population Dynamics (AGED)", funded by Ministero dell'Università e della Ricerca PRIN 2017 (20177PJ9XF\_005). Project PI: David Caramelli (University of Florence); Partners: Silvia Ghirotto (Università di Ferrara), Olga Rickards (Università di Roma Tor Vergata), Luca Sineo (Università di Palermo), and Lucia Sarti (Università di Siena).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** The authors wish to dedicate this article to the memory of Sebastiano Tusa. The authors would like to thank the anonymous reviewers for their helpful readings and suggestions that improved the overall quality of the text.

**Conflicts of Interest:** The authors declare no conflict of interest.
