title: Distinctive Paleo-Indian migration routes from Beringia marked by two rare mtDNA haplogroups.
abstract: BACKGROUND
  It is widely accepted that the ancestors of Native Americans arrived in the New World via Beringia approximately 10 to 30 thousand years ago (kya). However, the arrival time(s), number of expansion events, and migration routes into the Western Hemisphere remain controversial because linguistic, archaeological, and genetic evidence have not yet provided coherent answers. Notably, most of the genetic evidence has been acquired from the analysis of the common pan-American mitochondrial DNA (mtDNA) haplogroups. In this study, we have instead identified and analyzed mtDNAs belonging to two rare Native American haplogroups named D4h3 and X2a.
  
  
  RESULTS
  Phylogeographic analyses at the highest level of molecular resolution (69 entire mitochondrial genomes) reveal that two almost concomitant paths of migration from Beringia led to the Paleo-Indian dispersal approximately 15-17 kya. Haplogroup D4h3 spread into the Americas along the Pacific coast, whereas X2a entered through the ice-free corridor between the Laurentide and Cordilleran ice sheets. The examination of an additional 276 entire mtDNA sequences provides similar entry times for all common Native American haplogroups, thus indicating at least a dual origin for Paleo- Indians.
  
  
  CONCLUSIONS
  A dual origin for the first Americans is a striking novelty from the genetic point of view, and it makes plausible a scenario positing that within a rather short period of time, there may have been several entries into the Americas from a dynamically changing Beringian source. Moreover, this implies that most probably more than one language family was carried along with the Paleo-Indians.
authors.affiliation: Dipartimento di Genetica e Microbiologia, Università di Pavia, 27100 Pavia, Italy.
authors.forename: Ugo A
authors.initials: UA
authors.lastname: Perego
authors.forename: Alessandro
authors.initials: A
authors.lastname: Achilli
authors.forename: Norman
authors.initials: N
authors.lastname: Angerhofer
authors.forename: Matteo
authors.initials: M
authors.lastname: Accetturo
authors.forename: Maria
authors.initials: M
authors.lastname: Pala
authors.forename: Anna
authors.initials: A
authors.lastname: Olivieri
authors.forename: Baharak
authors.initials: B
authors.lastname: Hooshiar Kashani
authors.forename: Kathleen H
authors.initials: KH
authors.lastname: Ritchie
authors.forename: Rosaria
authors.initials: R
authors.lastname: Scozzari
authors.forename: Qing-Peng
authors.initials: QP
authors.lastname: Kong
authors.forename: Natalie M
authors.initials: NM
authors.lastname: Myres
authors.forename: Antonio
authors.initials: A
authors.lastname: Salas
authors.forename: Ornella
authors.initials: O
authors.lastname: Semino
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Bandelt
authors.forename: Scott R
authors.initials: SR
authors.lastname: Woodward
authors.forename: Antonio
authors.initials: A
authors.lastname: Torroni
mesh_terms: D001483:Base Sequence; D004272:DNA, Mitochondrial / Q000235:genetics*; D004641:Emigration and Immigration / Q000266:history*; D019143:Evolution, Molecular; D005843:Geography; D006239:Haplotypes / Q000235:genetics*; D049690:History, Ancient; D006801:Humans; D007198:Indians, North American / Q000235:genetics* / Q000266:history*; D016013:Likelihood Functions; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial