Read the following passage carefully.
While venom is most frequently associated with reptiles and certain arthropods, its presence in mammals, though rare, offers a compelling case study in convergent evolution. The venom delivery systems of the platypus (*Ornithorhynchus anatinus*), the Hispaniolan solenodon (*Solenodon paradoxus*), and several species of shrew evolved entirely independently of one another, separated by tens of millions of years of mammalian divergence. Morphological analysis reveals stark differences in the mechanics of envenomation: the platypus utilizes a keratinous spur on its hind limb, exclusively present in males and seasonally active during breeding, suggesting a role primarily in intraspecific competition rather than predation. Conversely, the solenodon delivers venom through specialized grooves in its second lower incisors, a morphological adaptation closely mirroring the rear-fanged mechanism seen in certain colubrid snakes. This dental venom delivery allows the solenodon to incapacitate vertebrate prey significantly larger than would be expected for an insectivore of its size.
Interestingly, genetic sequencing of the toxins produced by these mammals reveals that their venom cocktails are heavily comprised of kallikrein-1 (KLK1) serine proteases. KLK1 proteins are ubiquitous in mammalian saliva, where they normally function in blood pressure regulation and tissue remodeling. The independent recruitment and subsequent mutation of the *KLK1* gene into a toxic weapon across disparate mammalian lineages illustrates evolutionary opportunism. Because the baseline physiological function of KLK1 involves lowering blood pressure, the mutated, overexpressed venom variants induce profound, sometimes lethal, hypotension in prey or rivals. The fact that the solenodon and the shrew, despite their separate evolutionary trajectories, both repurposed the exact same salivary protein family for predation strongly implies that the genetic architecture of mammalian saliva intrinsically predisposes certain protein families toward toxic derivation when evolutionary pressures favor the development of venom.
Statement: Based on the passage, it can be logically inferred that prior to the evolutionary divergence of the platypus, the solenodon, and the shrew lineages, their common non-venomous mammalian ancestor likely possessed an unmutated version of the *KLK1* gene.
Cevap: Cevap