Razyn, I am reading this post:
The fundamental difference between the "SNP method" and any of the "STR
methods", is that SNP's are effectively unique events, whereas an STR value
can be a mutation from a higher value or a lower value.
So SNP mutations just regularly accumulate on the Y-chromosome in roughly a
constant manner as the generations go by - so counting SNP mutations is
effectively a simple clock.
In contrast, STR values can mutate up or down or stay the same as the
generations go by - so it is a more complicated clock mechanism to
untangle. That affects the uncertainty. Many STR markers are needed to help
extract a timeline for the STR method.
In regards to 18,692 snps, I meant to say "18,692 variable sites". I have
corrected the title in the graphic at the bottom ofhttp://www.goggo.com/terry/HaplogroupI1/
Out of the many millions of nucleotides sequenced on each of the 526
Y-chromosomes sampled, only 18,692 nucleotide sites varied. All the other
sites were the same. A bigger sample of people would identify further
variable sites on the Y-chromosome.
But who is Terry Robb?
Rich, have you found the link?