Changing the way we look at the world
Tales about tails

I have been reading about some research which is claimed to provide a mechanism by which primates lost their tails (click here to read the paper). This is important for evolutionists who believe that our ancestors had tails.

The authors of the paper studied the Alu elements (bits of DNA which control the expression of genes) associated with a gene called TBXT. In animals with tails this gene is involved in formation of the tail. Primates without tails also have a similar gene which is vital for normal development. In primates the TBXT gene has a different Alu element which controls the expression of this gene.
Scientists were able to change the expression of the TBXT gene in mice by deleting part of the gene so that it functioned in a way that is similar to the way it works in tailless primates. When this specific part of mouse gene was removed it caused fatal neural tube defects in animals which were homozygous for the deletion. 
Only heterozygotes survived and a few of them had no tail and others had short or ‘kinked’ tails. In total about a third of them either had no tail or a defective tail, the rest had normal tails. 

The authors believe that this shows a possible genetic mechanism for tails loss in primates. 
However, there are many unanswered questions. Let’s look at some of the assumptions which lead evolutionists to this conclusion. The first is the belief that we are descended from other mammals with tails. There is no hard evidence for this. The other is the belief that we lost our tails because it conferred an evolutionary advantage. 
There are serious problems with the idea that a random insertion of an Alu element resulted in tail loss. First, we are not just primates without tails. In passing we should remember that what evolutionists like to call the ‘tail bone’ is not a tail by any definition. We have a coccyx made out of flattish bones at the base of our spines, which is an important part of the human anatomy. 

The occurrence of neural tube defects which resulted from this sort of change to the TBXT gene would ensure that the tailless phenotype would not survive. It is hard to see how this gene could become fixed in the population when it causes defects which would strongly select against this phenotype. 

In order to overcome this objection, it is suggested that there was some other completely unknown selective advantage large enough to offset the deleterious neural tube defects (which are 100% fatal in homozygotes). 
Given that animals with tails seem to survive as well as animals without tails any hypothetical selective advantage would appear to be very small. It seems that animals without tails have no selective advantage over those with tails. Without a clear and very large selective advantage of not having a tail compared with having a tail there is no mechanism for evolving tail loss. 

A biologist who believes in creation, would interpret this evidence differently. The coccyx is designed to function as a key part of the human anatomy. There is no need for an evolutionary pathway from a post-anal tail to the coccyx.

As for the function of the TBXT gene in humans and tail less primates; it is possible that it is involved in formation of the coccyx. However, it should be noted that genes rarely have only one function and usually have wide ranging effects as part of a gene networks. The occurrence of similar genes in all different kinds of animals is an example of effective re-tooling of designed gene networks which control development. In this case the TBXT gene and its control sequences would seem to be regulating the terminal part of the spine, whether that is a tail or a coccyx.