It isn't the fact that there are two mutations that defines two lineages. One lineage is different from the other at two positions. The mutations defining these

It isn't the fact that there are two mutations that defines two lineages. One lineage is different from the other at two positions. The mutations defining these two lineages could have occurred in either animals or humans. What it does imply is that SARS-CoV2 was circulating at the Wuhan market for at least weeks or months before the first samples were collected. However, two base changes is very little data from which to construct a phylogenetic relationship or make "molecular clock" calculations.