Alright, we all know about the Superfacehugger, right? My theory is this: The Alpha alien lays one egg that produces a Superfacehugger, and saves it for "back-up" in case the hive gets destroyed. The superfacehugger implants an organism with a Queen, but also implants another organism with a "Halfling" which will absorb an abnormal amount of DNA from the host, thus creating a new type of Alien that will be more suited for life on the planet. Because it is so well-suited, it will ensure the survival of the queen, therefore securing a new hive. Now, suppose the queen gets killed, and it's up to the alpha (more than likely the hybrid) to create a new superfacehugger egg. This time, the embryo the superfacehugger lays will have a small slice of the DNA from the hybrid. The resulting Queen will have a few characteristics of the hybrid. Now, every egg the queen lays will have a few of her characteristics. Gradually, every time a hive is destroyed, the next generation will "weed out" the old genes in favor of new ones which will allow for more efficiency. This is possibly how they evolve. Now, the problem with this is AVP’s predalien at the end. The “fixer-upper†of this is quite simple: Ignore AVP. The preds look wrong, the aliens look wrong, the Bishop character is goofed up, ect. BOOM! You fix the entire timeline.