Editing Thuja (section)

== Evolution and paleobiogeography ==
Current research suggests that ''Thuja'' originated in the Americas and migrated to East Asia via the [[Bering land bridge]] in the [[Miocene]]. Fossil records show that Thuja was significantly more widely distributed during the late [[Cretaceous]] and [[early Tertiary]] than we see today.<ref>{{Cite journal|last1=Peng|first1=Dan|last2=Wang|first2=Xiao-Quan|date=June 2008|title=Reticulate evolution in Thuja inferred from multiple gene sequences: Implications for the study of biogeographical disjunction between eastern Asia and North America|journal=Molecular Phylogenetics and Evolution|volume=47|issue=3|pages=1190–1202|doi=10.1016/j.ympev.2008.02.001|pmid=18346917|bibcode=2008MolPE..47.1190P |issn=1055-7903}}</ref> The oldest known ''Thuja'' fossil is of ''T. polaris'' (an extinct species) from the Paleocene of Ellesmere Island in present-day Nunavut, Canada.<ref name="Cui e0138544" />

Other hypotheses of ''Thuja'' origin involved an East Asian origin, with the genus migrating twice; once east into North-western America and then west to the North-eastern America, but since no reliable fossil records of ''Thuja'' exist in either Western Asia or Europe, the possibility can be eliminated.<ref name="Cui e0138544"/>