At the beginning of "Prometheus," why did the Engineer need to die in order to seed life?

Question

The more I watch Prometheus (2012), the more I am confused with the beginning of the movie when an engineer is seen drinking that black liquid which turns out to be a chemical weapon to destroy all humans on earth.

There are many discussions online regarding that scene and the consensus is that that engineer went to earth to drink the black goo to spread his DNA for life to start on earth. However, very clearly, throughout the movie, we get to understand that that black goo is, in fact, a chemical weapon of sort, or at least a DNA catalyst.

The engineers were clearly an advanced species so why would they send one of their own to die just to create us? Surely they would be capable to use their DNA for the creation of life in easier ways.

There is a slight hypothesis in the movie that there were some differences of opinion in their society. Can we entertain the fact that, like in all societies, some were "criminals"? Is the engineer at the beginning of the film one of those sent to be terminated, using the black goo?

Some of his DNA manages to tear away from the goo and survives. Was it by pure chance that terrestrial life was created by the engineers? They clearly returned to see us throughout our evolution to possibly realise we were not worth being created?

And why are we so different from them physically?

Is there any evidence from the production team at Brandywine, or even Ridley Scott himself, to stop the speculations?

Answer 1

If you look at the alternate beginning scene on the Blu-ray, you find that this was actually a sacrificial ceremony attended by multiple engineers. Once the Engineer breaks up into tiny pieces and falls into the river, you're shown a few extra seconds of footage that explains that the sacrifice was meant to boot up the human evolutionary journey.

About the opening, Ridley Scott says that it could be any planet, at any time. This scene was representational of the ongoing efforts of the Engineers to bring life to planets.

From Todd Gardiner in Quora:

The Engineer was on a lifeless planet (one of many). He knowingly drank the black fluid, accepting with peace that this would end his life. His body was torn apart, seeding the planet with fragments of his DNA, which eventually formed the life on whatever planet he was on.

If it was Earth, this happened about a billion years ago; although this timeline might be off by a lot, since this explanation for life on Earth mixes intelligent design (DNA seeding) with evolution to get to what we have for life today.

By Aneef Rehman :

1. He drank it to sacrifice himself and seed Earth with genetic material to generate life.

2. He was an Engineer (an alien race that 'engineered' life). Presumably he was quite high in the Engineer social order as it seems to have been almost a religious ceremony so he could have been specifically 'chosen' for the task.

3. I think he was on Earth. Ridley Scott has said in an interview that it could have been any planet, it isn't specific.

4. I'm guessing that his DNA broke down and mutated to different forms to seed the building blocks of life.

5. I think that yes, he did know it would kill him.

6. I think the scene was to give a bit more depth to the Engineers and establish them as their namesake.

7. I guess it was around 3 billion years ago if it was the true genesis of life on earth, but this figure could be wildly off.

8. The ship was the ship that took the Engineer to earth. It was of a different design that the Engineer ships seen later but this is reasonable if it were such a large time difference. Or it was a different class of ship than seen later on.