When did lice appear? - briefly
Lice originated during the Mesozoic era, with the earliest fossil specimens found in mid‑Cretaceous amber dated to about 100 million years ago. Molecular analyses suggest the group may have diverged even earlier, in the Triassic.
When did lice appear? - in detail
Lice are ectoparasitic insects that first evolved in the Mesozoic Era. Fossil evidence from Cretaceous amber, dated to about 100 million years ago, records the earliest known specimens. Molecular‑clock analyses extend the origin of the lineage to the Jurassic, roughly 165 million years ago, when the ancestors of modern birds and mammals began diversifying.
Two principal suborders differentiate the groups that infest vertebrates:
- Chewing lice (Mallophaga): associated primarily with avian hosts; divergence estimates place their emergence around 100 million years ago, coinciding with the radiation of early birds.
- Sucking lice (Anoplura): specialized for mammalian hosts; phylogenetic studies suggest they originated near the Cretaceous–Paleogene boundary, approximately 70 million years ago, as mammals diversified after the extinction of non‑avian dinosaurs.
The evolutionary timeline reflects a co‑evolutionary pattern: as birds and mammals evolved new feather or hair structures, lice adapted correspondingly, leading to the extensive host specificity observed today.