Cat biology looks incompetent at first glance. Here is a hunter that cannot synthesise taurine, cannot convert carotenoids into vitamin A, and depends on dietary arachidonic acid and ready‑made vitamin D. Yet that fragility is the residue of past abundance, not a design error.
Evolution, being a ruthless cost cutter, trims any metabolic pathway that no longer shifts survival odds. In ancestral wild cats, prey tissues already carried taurine, preformed retinol, arachidonic acid and cholecalciferol in every successful kill, so maintaining the full enzymatic machinery for biosynthesis brought energetic cost without measurable gain. Genes for key enzymes, such as those in taurine biosynthesis and carotenoid conversion, accumulated mutations; natural selection simply stopped paying to repair them.
The result is a specialist with razor focus. Obligate carnivory lets cats optimise dentition, digestive transit time and hepatic enzyme profiles for protein and fat, while jettisoning carbohydrate handling and redundant anabolic routes. That creates a narrow ecological niche with a built‑in risk: when prey quality or availability collapses, there is no metabolic fallback, only dependence on another animal’s chemistry frozen in muscle, liver and fat.
