David couldn't possibly have been the one to... *SPOILERS*

There's no way that David could have created the Egg/Facehugger and subsequent Xenomorph. The derelict ship crashed on LV-426 roughly 2,000 years prior to the events of Alien. I say this because the Space Jockey/Engineer was "fossilized" to the chair.

This lines up with the events of Prometheus very well in that when they examined the Engineer's head they were able to determine it was about 2,000 years old. So, the logical conclusion is that the Derelict ship was one of the ships that fled LV-422, and crashed on LV-426 shortly thereafter due to an outbreak of the cargo.

With all this information there is absolutely no possible way David could have made the eggs that were on the Derelict as the timeline couldn't possibly match up whatsoever.

What I do believe is that either the Engineers found the eggs and reverse engineered them to make the black goo while still keeping and using the eggs as well, and David was able to take the black goo back to the egg again.

Or possibly more feasible is that the Engineers found or created the goo and used it to then create the Eggs/Xenos and David is simply figuring out the process the same way they did.

I just wanted to get my thoughts out there on the subject for everyone because the whole David creating aspect of A:C seems to be throwing people of thinking David is the true originator of the "Alien" species as we know it.