Fellow hominids! You wanna know HOW you lost your tails some 20 million of years ago?
In brief, this piece of DNA called an "Alu" jumped around the genome and inserted itself into TBXT, a gene controlling tail length, and voila! THAT curly appendix was gone forever.
From Nature
"On the genetic basis of tail-loss evolution in humans and apes"
https://www.nature.com/articles/s41586-024-07095-8
"The loss of the tail is among the most notable anatomical changes to have occurred along the evolutionary lineage leading to humans and to the ‘anthropomorphous apes’1,2,3, with a proposed role in contributing to human bipedalism4,5,6. Yet, the genetic mechanism that facilitated tail-loss evolution in hominoids remains unknown. Here we present evidence that an individual insertion of an Alu element in the genome of the hominoid ancestor may have contributed to tail-loss evolution. We demonstrate that this Alu element—inserted into an intron of the TBXT gene7,8,9—pairs with a neighbouring ancestral Alu element encoded in the reverse genomic orientation and leads to a hominoid-specific alternative splicing event.”