However, this haplogroup is now believed to have originated over 12,000 years more recently than previously thought, at only 5,000 years ago. According to 2009 studies by Bramanti et al. and Malmström et al. on mtDNA, related western European populations appear to be largely from the neolithic and not paleolithic era, as previously thought. There was discontinuity between mesolithic central Europe and modern European populations mainly due to an extremely high frequency of haplogroup U (particularly U5) types in mesolithic central European sites.