caution, external references needed:

opening scene...that 'guy' drinking something? what's that all about?

sorry if this is a silly question

Well the biological aspect was definitely not being scientifically consulted...

Any biologist with the most basic credentials will point out the serious errors as presented in the movie.

1. Free flowing DNA in raging water. DNA alone does not produce life and being dispersed at such a large volume of water will bring the probability of proteins and random DNA coming together to 0%. For life to start you need shallow concentrated pools with random chemicals forming amino acids, lipids and probable nucleic acids.

2. The DNA was shown to be very short fragments (100bp or less) single stranded DNA. To be broken down to such an extend and to able to reform back to the engineers' original chromosomal sequences is again 0%. Homo sapien is not the only hominid in evolutionary history nor are humans the only animal species in the world. This relation is a fixed genetic variability can be calculated and determined.

3. The human genome (3 Gigabase haploid) is a testament of evolution, about only 2% codes for proteins and another 2% are are transcriptional involved, while the rest of the genome is yet unknown but it's safe to say for a fully functional human, a much lesser genome size can exist (probably just 20% is needed). Which is also why human as the most successful species now, does not have the largest genome in the animal kingdom. Some "lower" level fish can even have a larger genome than human. Accumulation of large non-functional regions of the genome is a testament of the evolutionary, life span, breeding frequency... etc. Because of the presumed long life span of the Engineers, their genome has to be different than human's. Even though an Engineer looks like YaoMing their genome can be/has to be different, and due to convergent evolution (as there are many examples on earth) similar characteristics/structure can exist.

4. A Eukaryotic somatic cell division was shown, this is not the first lifeforms on earth .... an argument can be made as showing further down time progression though.

Therefore Ripley Scott and the Lost script writer (and another) are out of their league. If you bring in a concept make sure you have the current science to back it up. Science fiction of old cannot be utilised now. If you don't know anything SciFi it out of your imagination shows the person's stupidity (is the best way that I can put it). This in a way is reflective/testament of the effort put in by Joss Whedon by putting SciFi and real science hand in hand that blew everyone away in the box-office (except James Cameron, another director working/consulting with the scientific community)