In order to survive, your primary need is simply to eat dinosaur meat. There are plenty of small dinosaurs on the island for you to hunt, but larger carnivores are nearly impossible to kill and are effective at preventing you from obtaining your food.
Cooperation is highly rewarded since the process of hunting becomes drastically easier. Groups of hunters will have the ability to build campsites, which can be used to store meat. Large quantities of stored meat will enable abilities for that group.
The more meat that is being stored by players, the fewer huntable dinosaurs will be present on the map. This will cause other tribes to seek down and destroy your campsites. Becoming the dominant tribe on the island is the ultimate goal.