One of the weaknesses of art that is based on a literary text is these texts tend to be culture specific. That is-while we might recognise a scene that has been visualized from The Bible say "The Crucifixion" we probably don't recognise a scene taken from ancient Greek mythology, its full meaning is lost to us unless we go to our research tools. An imaginative visualisation from a literary narrative is also quite a different process to the original impetus of the writer. Where details can be a given in a text this is not so for a painting or sculpture. In the Bible for instance there are no physical descriptions of the protagonists and in many renaissance paintings Jesus and his mother Mary look approximately the same age. What did Mary look like ? What did Jesus/Peter/Paul/James etc look like ? Our "picture" of Jesus is a product of the paintings and sculptures that were made from a detail poor biblical narrative. This is also true of how people dressed-the dwellings they inhabited etc.
What can we recognise about it now we have researched the sculpture's origins ? We are looking at the high point of the drama. An artist in theory could make a visual work of any point in the time line of a narrative-the snakes coming out of the sea, the dead bodies of Laocoon and sons, the moment Laocoon sees the snakes etc. It is easily argued though that none of those possibilities has the high drama of the moment of the living victims in the coils of the snakes. Artists must make judgements like these to realise a work of art. The use of nudity rather than clothing the figures dramatises their struggle.
The apparent age of the sons is also I believe a considered element in the drama. Their youth suggests an innocence that increases the cruelty of the punishment inflicted by the god. Here too is a subtle and balanced artistic judgement, their physique suggests an older male while their size suggests a youth, had their physique matched their apparent age the unity of the sculpture would be lost, if their age matched their physique the emotional impact would be lessened. Further-if by reducing the age of the sons the emotional impact is heightened why not represent them as even younger ? I suspect that if the sons had been represented as any younger that aspect of the physique may have become too grotesque-a very young boy with "manly" physique would render the sculpture laughable. While it is easy to dismiss older works as "conventional" and of no real value to us now I think that if we can get past the misgivings we have about such work they are still rich in lessons for any art student willing to look and think about what they are looking at.
The Laocoon sculpture is also significant on another level. It was unearthed in Rome a year or two before Michaelangelo began work on the Sistine Chapel and it is known that he knew the sculpture well. I believe the impact the sculpture had on him was a decisive element in the approach he took to the Sistine Chapel ceiling.