Cross posted from the UA/barnacle mega-thread as it seemed relevant to put it here too for discussion:
In light of Mr Braben's recent confirmation that barnacles are indeed a lifeform/living creature:
One thing that all living creatures have in common is the need and ability to reproduce. With barnacles it's clear that they spread to other planets when they do so.
The only mechanism we've seen so far to do this are the UAs. Theories have already been put forward that they are seeds or a juvenile form of the barnacle (as others have pointed out if you look at the top section, it looks like an unformed barnacle).
The UAs are seemingly spread by being collected by curious explorers (a type of space farer that tends to be curious by their very nature) who love to go to nebulae where they are located in a shell approximately 150LY around them.
They then cause the ship to decay which leads to them crashing on planets in some cases which allows the barnacles to spread to these new locations.
Their collection and distribution is very similar to birds eating fruit and then depositing the seeds elsewhere except more parasitic in nature.
The barnacles also however have some sort of mark on them which would lead one to believe that they have been made, or at the very least genetically branded, by someone or something.
They also need a relatively new invention (space ships) to allow them to reproduce and successfully spread their seed which would mean they are unlikely to have evolved in the manner that they have without some sort of intervention/creation by another intelligence unless other forms of spaceships that enjoy travelling to nebulae have been around for millions of years.
If they have been engineered then what is their purpose? Is it communication? Are we supposed to work out what the symbol means and try and communicate with them, or is the symbol on them a warning or territorial marker?
Are they slowly terraforming planets to make them suitable for a race that intends to occupy them at a later date or are they perhaps there for another race to mine the minerals that we see produced when they are destroyed/harvested like a crop? If so, how will they react when they see that we have already plundered the resources that they went to such great efforts to gather?
Further studies are required.