What could be done – single cell birth dating

The famous Spalding paper 2005 used an interesting approach

We show that the level of 14C in genomic DNA closely parallels atmospheric levels and can be used to establish the time point when the DNA was synthesized and cells were born… Retrospective birth dating is a generally applicable strategy that can be used to measure cell turn-over in man under physiological and pathological conditions.

I was more in favor of calculating mutation rates, S. Horvath suggested methylation changes. Maybe lineage tracking will be the next big thing in single cell analysis and the human cell atlas?