As promised earlier, I would like to talk briefly about the discrepancies in the Origin idea of Prometheus. My hypothesis was that the engineers had seeded life here on earth and did not intervene with already evolving life on the planet. I had opined that the engineer sacrifice happened sometime in the Archean eon (3.9-3.8 billion years ago). But, I had also noted a problem – The engineer being able to breathe without any external aid on primordial earth, when there was no free oxygen in the atmosphere. The reason being that photosynthesis evolved only around 2.5 billion years ago that resulted in an oxygenated atmosphere, but life had long existed.
From a photography standpoint, it is a well known fact that the origin scene was shot at the Dettifoss Waterfall in Iceland. It surely was an absolutely fantastic location for the shot. If you watch the events leading to the waterfall scene, you could observe something. As the camera spans over the landscape of the terrain (from the vantage point of the Engineer’s spacecraft) leading up to the waterfall, you could see a large number of green patches (algae, grass, etc.). Technically, the presence of greenery would support the engineer experiencing no breathing issue. But it doesn’t go along with the cell division scenario a tad bit later that suggests that life started due to the engineer’s intervention.
Due to all this, I would assume that it was simply something that they had overlooked in the shoot. If they hadn’t shown the green, and put some kinda mask on the engineer, it would have been perfect (Can Damien or Ridley shed more light on this?).
The mask thing is not that much of a big deal though. Going by the biology of the engineers (Actually, this is another theme that is fascinating to speculate – more later, of course), I would say that the engineers have some extreme form of Cyanosis. It is a condition that causes bluish coloration of the skin membrane due to low oxygen levels in blood. The fact that the engineers are pale bluish, may I suggest that they come from a planet, perhaps with low levels of oxygen in their atmosphere and that their respiratory system has evolved to take care of this issue? Perhaps, they are adapted to thrive in such conditions and can survive for shorter times in an oxygen free atmosphere? That’s why the engineer shows no discomfort breathing for the limited time that he is on prehistoric earth.