A comprehensive, diachronic and comparative picture of the mitogenome variation along the Americas

Native Americans present a remarkable case study in human evolution and population genetics. They belong to one of the few extant human groups whose ancestors entered a vast uninhabited area over a relatively short interval and then apparently remained relatively isolated from other human groups for a considerable period of time before European contact. Their substantial cultural diversity, linguistic complexity, and biological variation has been the subjects of a plethora of studies, whose level of sophistication has consistently grown over the past 40 years, but to date has not yet seen a final consensus among the disciplines involved. After all these years, this debate is still ongoing among scientists regarding major issues such as the number of migratory events, the source populations and arrival timing, and the likely entry routes into the Americas. Even the archaeological evidence is inconsistent as the dating of skeletal remains and Clovis lithic artifacts yielded values of 13- 14,000 years before present (YBP), while other archeological studies reported sites with dating to more than 33,000 YBP. The overall picture is gradually emerging much clearer and detailed thanks to the contributions provided by human genetics and genomics studies. The first pieces were provided by analyses of the so-called "classical" genetic markers; subsequent findings came from the phylogenetic surveys of uniparentally transmitted genetic systems, in particular from mitochondrial DNA; then in the last few years, further valuable details were delivered by a new phase characterized by ancient DNA analyses. Here, we present a comprehensive, diachronic and comparative picture of the mitogenome variation along the double continent. More than 1600 entire mitochondrial DNAs from modern samples (were gathered from literature and unpublished databases and compared with ca. 90 novel ancient pre-European contact mitogenomes (mostly from North America) in order to reconstruct the migratory path(s) of ancient native populations and to evaluate the differential demographic impact of post- European contact in South and North America