Any L23XL51 clades whose downstream SNPs post-date L51 could still be ancestral to L51 as SNPs that post-date L51 could have subsequently occurred in the ancestral line (in fact its inevitable if we had enough SNP resolution). So, are any of the L23XL51 subclades potentially younger than L51? Obviously to know that we have to decide how old L51 is and Mjost recently suggested it may be older than we thought? Have variance dates been calculated for all L23XL51 clades?