In the study of supercentenarian woman here, it was found that all her blood cells are formed from only two stem cells (ancestor stem cells).
How scientists can distinguish cell ancestors?
Aren't all genes of one body identical?
If there are somatic mutations, which are increasing while lifetime, then how they could know, that there are more ancestor stem cells in childhood? Shouldn't it be less mutations and cell lines less distinguishable?
May be stem cells only can be counted in oldness.
Then how is it possible to know, that there are 20000 of stem cells at birth?