https://www.hillspet.com.au/cat-care/behavior-appearance/why...
Do we have evidence cats’ ancestors had such a receptor?
If not, it might be simpler to assume there wasn’t evolutionary pressure to not taste sweetness as much as there was a lack of any pressure to taste it.
I'm not a biologist, but the lack of that gene is very conserved across all Felidae, I think (i.e. there isn't a single felid that can taste sweetness) which usually indicates that there's some evolutionary pressure.
The gene is present in all (most?) other mammals except cats. One can reasonably assume that there was some evolutionary pressure to it. A whole family/species most likely does not lose a gene without some major outside pressure. Either the population shrinks suddenly and is recovered from individuals missing the gene, or that gene is eliminated presumably for good reason. This is not evidence but it's the more likely explanation.
Of course laser eyes are great only for the first individual that evolves them. Then basically every other population tends to start dying off because you can't just not use them.
An example in primates is the loss of Vitamin C synthesis, which would have been a handy adaptation during the Age of Sail, but the gene was lost at a time when our common ancestor at a fruit-heavy diet.
They say that all mammals studied so far, including ones close to cats, have the gene except cats... This seems to almost demonstrate that cats must have lost that gene at some point.
I think you meant "felines".
[UPDATE] Nope, the OP meant felids (though my old eyes parsed it as "fields" (never heard of a "felid" before) which is why I thought it was spell checking or voice recognition gone wrong).