The Xenomorphs in the Alien saga have been described as being the perfect organisms as they are extremely intelligent and incredibly hard to kill, and the series hints that the Predators have something to do with that evolution. Xenomorphs have no shortage of ways to kill their prey with their claws, teeth, inner-mouth, and razor tail, though one of their weapons stands above the rest as it is the perfect defense against a species that loves to fight up close and personal.
In Aliens: Hive #4 by Jerry Prosser and Kelley Jones, surveyors are investigating a Xenomorph hive that has been claimed by the company Neo-Pharm, a pharmaceutical company that collects the slime produced by Ovomorphs and refines it into a drug known as Royal Jelly. Once the Xenomorphs launch an attack, the surveyors are doing everything they can to get out of there alive, and all of the deadly excitement is observed by a scientist who has committed years of his life to Xenomorph research.
The scientist watching the events unfold witnesses one of the people trapped in the hive launch an attack against a pursuing Xenomorph, killing the beast with a toss of a grenade. With the Xenomorph’s death comes the secondary attack all of its species have in store: a spray of acid blood. The scientist comments to himself, “I would hate to encounter the predator that acid defense was evolved to thwart” with emphasis made on the word ‘predator’. This comment hints that Xenomorph biology evolved to combat Predators as it is well known that the two species exist in the same universe within the continuity of Dark Horse Comics.
In the shared universe inhabited by Predators and Xenomorphs, the Predators were responsible for spreading the Xenomorphs across the universe so that they had plenty of opportunities to hunt the beasts. Since the Predators have been a constant threat to the Xenomorphs since their earliest history, it makes sense that their biology would naturally evolve to fend off the Predators.
If the Predators are responsible for the Xenomorphs’ deadliest weapons, then it only makes sense that the Xenomorphs were responsible for theirs. The targeted laser blaster the Predators carry on their shoulders is one of the only long-distance weapons the Predators carry with the rest of their weaponry used for close combat. If the Xenomorphs evolved acid blood to defend against the Predators, then perhaps the Predators developed that piece of tech to kill Xenomorphs from a safer distance. While neither prospects are confirmed, it is heavily hinted at in this issue that at least one of them might be true, as Alien’s Xenomorphs may have evolved their deadliest weapon to kill Predators.