When did ticks appear? - briefly
Ticks first emerged during the Devonian period, about 400 million years ago. Fossil records indicate they evolved from early arachnid ancestors.
When did ticks appear? - in detail
Ticks belong to the order Acari, suborder Ixodida. Fossil evidence places their first appearance in the early to middle Jurassic, roughly 180–165 million years ago. The oldest confirmed ixodid specimens are preserved in amber from the Karabastau Formation (Kazakhstan) and the Jurassic–Cretaceous boundary deposits of Myanmar, showing morphological features of modern hard ticks (Ixodidae). Soft ticks (Argasidae) have a slightly later record, with specimens from Cretaceous amber dating to about 100 million years ago.
Molecular‑clock analyses, calibrated with these fossils, estimate the divergence of the major tick lineages between 200 and 150 million years ago. The split between hard and soft ticks is inferred to have occurred near the Jurassic–Cretaceous transition, coinciding with the radiation of vertebrate hosts such as early mammals and dinosaurs.
Key points summarizing the evolutionary timeline:
- Early Jurassic (≈180 Mya): First hard‑tick fossils appear; body plan already includes capitulum, scutum, and chelicerae.
- Mid‑Cretaceous (≈100 Mya): Soft‑tick fossils emerge; adaptations for rapid blood‑feeding on avian and reptilian hosts.
- Late Cretaceous to Paleogene (≈70–50 Mya): Diversification of genera linked to the rise of modern mammals and birds.
- Neogene (≈23 Mya onward): Expansion of tick species diversity, driven by climatic shifts and host‑habitat specialization.
The convergence of paleontological data and genetic dating supports a Jurassic origin for ticks, with subsequent diversification driven by the emergence and evolution of vertebrate hosts.