Editing Cactus (section)

===Evolutionary history===

No known fossils of cacti exist to throw light on their evolutionary history.<ref name=ArakChriNyffLend11/> However, the geographical distribution of cacti offers some evidence. Except for a relatively recent spread of ''[[Rhipsalis baccifera]]'' to parts of the [[Old World]], cacti are plants of [[South America]] and mainly southern regions of [[North America]]. This suggests the family must have evolved after the ancient continent of [[Gondwana]] split into South America and [[Africa]], which occurred during the [[Early Cretaceous]], around {{Period span/brief|Early Cretaceous}}.{{sfnp|ps=none|Anderson|2001|pp=37–38}} Precisely when after this split cacti evolved is less clear. Older sources suggest an early origin around 90 – 66 million years ago, during the [[Late Cretaceous]]. More recent molecular studies suggest a much younger origin, perhaps in very Late [[Eocene]] to early [[Oligocene]] periods, around 35–30&nbsp;million years ago.<ref name=ArakChriNyffLend11/><ref name=Nyff02/> Based on the phylogeny of the cacti, the earliest diverging group (''Leuenbergeria'') may have originated in Central America and northern South America, whereas the caulocacti, those with more-or-less succulent stems, evolved later in the southern part of South America, and then moved northwards.<ref name=EdwaNyffDono05/> Core cacti, those with strongly succulent stems, are estimated to have evolved around 25&nbsp;million years ago.<ref name=ArakChriNyffLend11/>  A possible stimulus to their evolution may have been uplifting in the central [[Andes]], some 25–20&nbsp;million years ago, which was associated with increasing and varying aridity.<ref name=EdwaNyffDono05/> However, the current species diversity of cacti is thought to have arisen only in the last 10–5&nbsp;million years (from the late [[Miocene]] into the [[Pliocene]]). Other succulent plants, such as the [[Aizoaceae]] in South Africa, the [[Didiereaceae]] in Madagascar and the genus ''[[Agave]]'' in the Americas, appear to have diversified at the same time, which coincided with a global expansion of arid environments.<ref name=ArakChriNyffLend11/>