Principle behind the TinT method. Examples of directed insertions of CR1 elements active at different periods. (A) Shows three different CR1 subytpes, active at non-overlapping periods and their resultant TinTs (in box below). As indicated by blue arrows, the youngest element (C2) inserted into both older subtypes (D2 and C4). D2 was active after C4 became inactive and inserted into the latter (red arrow). (B) Example of CR1 subtypes active at overlapping and non-overlapping periods. Only elements that were active during overlapping periods (C2 and B2) had the opportunity to insert each into the other. As the activity period of the B2 element only partially overlapped that of the C2, fewer insertions occurred in the B2-C2 direction (indicated by the thinner arrow). (C) Example of three CR1 subtypes active at overlapping periods. Note that the activity of C4 does not overlap that of F0, thus there was no opportunity for C4 to insert directly into F0. Again, fewer insertions of older elements into younger ones are indicated by thinner arrows.