When you hear me spinning my rich tapestry of narrative about the melonheads creating Homo Sapiens, you should know that I am good at coming up with explanations that satisfy Ockham's Razor and they also hit the key facts of the matter with nice, tidy explanations where most of the orthodoxy has failed to even cover the bases.
That does not mean that I am correct, however. It may mean that I am one of the rare people who is even bothering to think seriously about this subject.
There are conventional albeit more pedestrian explanations that do not require quite as many suspensions of disbelief. I thought you might like to hear some of them so you'd be able to think about them yourself.
1. It is possible that the ruling classes have never produced slaves through genetic engineering, unless you consider interbreeding with your own social class a form of genetic engineering ... and it most certainly is, except with longer spans of time involved to produce outcomes. It is possible that the slave classes and the ruling classes have been produced throughout human history the same way, simple marriage. The more the rich marry the rich and the poor marry the poor, the rich get smarter and the poor get more slavelike. It is also possible that one of the mythologies fostered by the ruling classes has been that they deliberately created slaves to serve their needs, when in fact they were simply available, just as they are available now.
2. It is possible that the Neanderthals were never an experiment that escaped their labs ... but simply a rugged independent race of men who always lived xenophobic and reclusive lives far away from the urban centers. In fact, it is possible that the ruling classes frequently told the slaves who worked on their infrastructure that the Neanderthals were their "creation" in order that their slaves believe that they were the masters of everything - and that nothing was outside their control. This could have given rise to the myths of Enki and his manufacture of slaves for the "gods." The rulers could have encouraged these myths amongst their slaves to promote the idea of their omnipotence and to convince their slaves that they had been made for the purpose of doing as they were told. Perhaps once in a while a slave would ask why the Neanderthals lived wild and free and they replied "Well, we permit them to do so, you see."
3. It is possible that the Nephilim may not have been hybrid monsters made from Neanderthal genes. Perhaps the Nephilim were Neanderthals who were willing to part with their freedom in exchange for the right incentives. Maybe some Neanderthals descended to the cities and took pride in becoming guards and "watchers" (Book of Enoch) for the pharoahs and the master royalty. It is unlikely all of them were so immune to the attraction of power and prestige. Maybe the ruling classes liked to scare their slaves by telling them that their palace guards were part monster to assure even the staunchest slaves would tremble at the thought of revolt.
4. Maybe Homo Sapiens was not a deliberate product of melonhead thirst for revenge. Perhaps he was any one of a number of things, all of them possibly explaining why he appeared so quickly out of nowhere. He could have constituted a breeding population of Neanderthal rejects, as suggested here before. This would explain why he suddenly "appeared" in Europe. Maybe he was always there, living a couple mountains away in villages of outcasts and misanthropic descendants of Neanderthals. This would explain very easily why he killed the Neanderthal males and took the females. He felt entitled to do so in revenge for himself or his great-grandfather, thrown out of a Neanderthal tribe for being damaged goods. One of the problems with being genetic snobs is that sooner or later, the rejects can outnumber you if your standards are too high. Especially if you get kicked out of the tribe for being obsessed with sex and lacking in self-control. Your breeding habits might not be the preference of other Neanderthals but you will come to outnumber them by a huge margin in demonstrating these traits.
5. Maybe the melonheads are really any genetics where intelligence is not coupled with compassion and where the cognitive elite simply do as the dumbest humans do except with a lot more brains to attain what they desire. Maybe anybody who is smart but immune to any charitable feelings for other humans based on their shared context is really a melonhead in training. Perhaps anybody born with the dumb luck to be very bright who does not temper it with some empathy for people not as bright as he is will always just be a monster waiting to happen. Remember, no matter how big your brain, there is probably a guy right around the corner with an even bigger one who regards you as "subhuman." Maybe there is really so little distance between all men, including melonheads, that any of them can make the same mistakes in life and be judged unworthy for it if they are not willing to pray for grace. If the ruling classes are really so bright then how come they can only make things worse and never better? Wouldn't it be something if they evinced real intelligence and could improve the lot of everyone else around them without having to put them into chains of one variety or another and steal away with what little they have? Now that would be a melonhead that was worth a damn.
6. Perhaps the ongoing tragedy of the planet is that no matter what time you live in or under what circumstances, the real curse of all these hominids of various flavors is that none of them is bright enough to achieve any lasting peace, build anything that persists for long before it is torn down or create any principle that is any more useful than any given sentence in the Bible. In this way they can all be lumped together as different varieties of failures. Perhaps forgiveness and redemption is what every single one of them truly needs and that means that Christ and the doctrine of grace applies equally to all of them no matter what they think of themselves. If this were the case, there is only one hominid definition that truly matters and it is the division of the repentant and the unrepentant. Once you start to see this the way that God might see it all, you will find yourself saying just like he probably does ... sorry, but they all look alike. There is not one of them that has not gone astray as soon as he is born. Some of them so far astray it is highly unlikely they would ever reform ... others there always seems to be some small hope for.
Pondering these things gives you another kind of perspective on this subject and no matter what, remember I'm no prophet or seer and can never say for sure what happened more than 100,000 years ago. I will always just be making educated guesses.