Evolution of Cactus ... 1/4

In the beginning ...

No fossils of early cacti have ever been found, because for a fossil to form there needs to be ample water for sedimentation or laying down of sediment over the plant like a plaster cast - an unlikely occurrence in the case of Cacti in a water scarce environment of the deserts. Also entombment in Ice or Amber is unlikely in the desert environment.

However DNA, molecular data and bio-geography (how geology e.g.. plate tectonics impacts on biology) has given us a few clues.

Relatives of Cacti

From DNA studies it has been found that the closest family to the cacti family is the Portulacaceae family ( e.g.. genera Portulaca, Talinum, and Anacampseros) and possibly Didiereacea family which places them in the Caryophyllales, which originated in Africa. Portulacaceae now occur in South Africa, Kerguelen Island and New Zealand - all part of the original Gondwanaland. Didiereaceae live on Madagascar - another part of Gondwanaland.
Which all makes sense as cacti are in the Americas, starting out in South America - another part of Gondwanaland.