Abstract: "Atavisms have attracted people’s attention for a long time. First, atavisms excited their imagination and created fertile ground for myths and superstitions. With the development of science, atavisms became the subject of investigation, which soon provided evidence to support evolutionary theory. However, at the molecular level, the formation of atavisms remained insufficiently understood. Recent progress in comparative genomics and molecular developmental biology has helped in understanding the processes underlying the formation of one of the human atavisms: the vestigial tail."

"Introduction: According Wilhelm Roux, the term “atavism” in biology defines the revival of a biological structure that was lost in ancestors during evolution (Correns et al., 1912). The term “atavism,” coined in 1766 by French botanist Duchenne [i.e. Antoine Nicolas Duchesne] comes from the Latin atavis, which roughly corresponds to the word “precursor” (Hall, 2010; Zanni and Opitz, 2013). We know several atavisms in humans: color blindness, extra nipples, enlarged teeth, an elongated coccyx (“tail”), excess hair, etc. The existence of atavisms is a big problem for creationists challenging evolution. Atavisms are the insurmountable argument of the theory of evolution, which contradicts the basic idea of creationism that animals and plants exist unchanged from the moment of their creation."

The authors stated that “The four genes that are the most likely candidates for the role of genes whose function causes the absence of tail are : 1) TBXT 2) Wnt3a 3) Tbx6 and 4) Msgn1. It is the functional deficiency of these that causes the absence of a tail”.  They also stated that TBXT is the most important of these genes. It is generally stated that mutations in these genes made them non-functional and caused the loss of a tail that resulted eventually in the hominid apes roughly about 18-25 million years ago, Once the tail disappeared, the hominid apes with no tail evolved, such as the Gibbon, Pongo and Gorilla, to a stage reaching the Pan (chimpanzee) species, which has the closest genetic lineage to man.

Open access at https://link.springer.com/article/10.1134/S1062360422030043

(Thanks to Juan Weiss for this reference and its interpretation.)