[itaborai83]

I´m not necessarily defending the movie, but I don´t think that Janek actually "solved" it, but I do think that that´s what they want us to believe. The black goo is not an weapon IMHO, but a way to accelerate the evolutionary process in a planet, bringing forth more adaptable lifeforms (without preserving the previous ones). That´s what is shown in the beginning of the movie. The engineers could be responsible for rapid evolutionary bursts throughout the history of our and other worlds.

Perhaps we, as a species, weren´t simply done yet. Something still had to burst out our collective chests in order for us to actualize our genetic potential. Maybe the xenomorphs were the ultimate monkeys out of which the definitive mankind would evolve from.

Piss poor execution though.