Figure 1

New method to estimate the insertion date of truncated copies. When a burst of amplification occurs, all the copies deriving from one master copy insert approximately at the same time. Upon insertion, all the new copies are identical in sequence as well as the two LTRs of each copy, leading to a null divergence between copies (Div = 0) and between the two LTRs of each copy (Div_LTRs = 0). Over time, all sequences evolve at the same rate, so both the divergence between two copies and the divergence between the two LTRs of one copy are equal at a given time. Hence, if the nucleotide divergence between a truncated copy and a copy with two LTRs ("2 LTRs" copy) is equal to the nucleotide divergence between the two LTRs of the "2 LTRs" copy, the two copies originated from the same burst of amplification and the insertion date estimated for the "2 LTRs" copy can be used as an approximation of the insertion date of the truncated one.