Re: Need some additional info regarding GENES FOR TAIL CONTROL IN HUMANS!
There may well not be the clear demonstration you wish. Human embryo's are a very valuable resource and consequently there is not a very wide set of in-situ characterisation of gene expression patterns in humans.
Similarly familial cases of real tails in humans are incredibly rare, I could only find one referenced in the literature, so there is very little scope for a proper genetic analysis to find a causative locus.
Less closely related groups, like insects do not use sonic hedgehog, but analogous chemicals.
Pretty misleading statement. The original hedgehog gene was identified in Drosophila, it is more arguably the vertebrates that have a diversified derivative gene family with many hedgehogs indian, desert and sonic.
How badly conserved does a protein need to be before you decide it is a distinct but analogous chemical?
What aspect of his evolutionary past was creeping up?
Arguably none, there is no reason why a mutation has to be an atavism (reversion to an ancestral state). Mutations occur producing embryos with 2 heads, that doesn't mean 2 headed organisms were part of those embryos' evolutionary lineage.
Did our ape ancestors have extra digits too?
The answer depends on what question exactly you are asking. If you mean did ancestral species of great apes commonly posess extra digits the answer is no. If you mean did our ape ancestors also suffer from the sporadic appearance of supernumerary digits, the answer is almost certainly yes.
If you go further back in the evolutionary history of tetrapods though you find many examples of primitive limbs with many more digits than modern tetrapods, principal ones being Acanthostega and Icthyostega with 8 and 7 digits respectively.
Considering the additional ossification and the webbed fingers the most likely developmental pathway to have been affected is probably BMP (Bone morphogenetic protein) which is associated with bone growth, obviously, and also with the regulation of apoptosis in interdigital regions which is responsible for removing the tissue that is present there in the early embryo. As for frog ancestors, certainly an amphibian ancestor is on the cards, again something along the lines of Acanthostega.