From a new U5 research paper [Emerging genetic patterns of the european neolithic: Perspectives from a late neolithic bell beaker burial site in Germany - Lee et al.], although the analytical methods and conclusions of this paper are being questioned by other researchers who believe present day European U5 haplogroups may be mostly descended from Mesolithic European U5 with some contribution from Neolithic European U5 and Neolithic U5 immigrants from the Near East and/or Asia.
To further investigate if U5-lineages from the Mesolithic/Neolithic are present among contemporary Europeans, modern DNA sequences were combined with those obtained from ancient individuals. The median-joining network does not show a clear center and aDNA sequences are distributed within shared haplotypes toward the central as well as derived haplotypes at the tips of branches (Fig. 3). And, most strikingly, the Mesolithic and Neolithic singletons placed at the tips of the branches suggest that these lineages did not continue into the present. Based on this haplotype distribution, due to genetic drift or some demographic event modern U5 haplotypes do not appear to have had significant contributions from the Mesolithic/Neolithic gene pool. At least for this haplogroup, it appears there is no simple story of continuity from the Neolithic to the present and that central Europe may have experienced complex demographic events since the Neolithic involving groups that harbored distinctive maternal lineages.