It was posted in an earlier post that competition and predator/prey relationships would happen in any type of system (environment, planet, etc.) and regardless of type of creatures (carbon based, silicon based, etc.). I would add that sentience is probably not even possible without competition. Of all of the intelligent species of the planet, it seems every single one is a predator. The indicators we use, communication, cooperative interaction, and "play" are all traits of predators.
On the subject of sentience, I don't think sentience is necessarily some threshold a creature has to achieve in order to be "intelligent". I think sentience is more of a range or spectrum. Just because we consider ourselves sentient doesn't mean we are necessarily the only aware species on the planet, or even the most aware species on the planet let alone in the universe.
There are many other species that would have a shot at achieving the level of awareness that we do, if nature and humanity give them the chance. Whether or not a species achieves our level of sentience is affected by a lot more than just the potential to achieve it. Some very specific things had to happen for mankind to achieve supremacy and the level of sentience we enjoy. Remove any one of those occurances and we could just as likely still be primative primates. In that situation there could just as likely have been another intelligent species gaining dominance and sentience, as there could be no sentient or dominant species. Intelligent species could be as much a product of chance as a product of competitive evolution.
Bringing this all back to the subject, intelligent alien races, regardless of form, would probably all have predatory origins. So, manipulation of their environment would be a must (whether hands, tentacles, telepathy, etc.). They would have to be able to "hunt".
Personally, I'd go with the cephalopods as the next best chance of a sentient creature also. I don't think their behaviors are any more sentient than other candidates (whales, dolphins, etc.) but just based on ability to manipulate their environment, I think cephalopods have the advantage. Although you can't rule out insects either.
Insects may have a leg up also (or
legs up
). The hive mind concept could be one where collective intelligence finally reaches a point of critical mass, and tips over into a level of awareness comparable to ours. I like
Mustrum Ridcullys reference to
The Swarm, with the idea of bacteria achieving a sentient hive mind. The Borg in
Star Trek are a good example, as are the Klicks in Star*Drive. A drone may not be very sentient on it's own, but the queen or a central/combined hive mind would be.
