| The proposed approach to terrestrial xenology has the attractive advantage not to require complex and sometimes very artificial scenarios for the early history of the Earth. |
| Usually these families are excluded from genome-wide analyses that assess HGT due to uncertainty of paralogy versus xenology. |
| In this case, xenology can be erroneously inferred. |
| That is, we might choose to define xenology and topohomology independently. |
| Once recognized and sorted out, paralogy and xenology can be viewed as features that enrich evolutionary histories. |
| An illustration of xenology due to horizontal gene transfer. |
