Question

How long ago did the common ancestor of all the organisms on this phylogenetic tree exist?

Answer 1

In biology and genealogy, the most recent common ancestor (MRCA, also last common ancestor LCA, or concestor[1]) of any set of organisms is the most recent individual from which all organisms in a group are directly descended. The term is also used reference to the ancestry of groups of genes (haplotypes) rather than organisms. The age of the human MRCA is unknown. It is necessarily younger than the age of both Y-MRCA and mt-MRCA, estimated at around 200,000 years, and it may be as recent as some 3,000 years ago.