The four cultic enclosures excavated so far are similar: they are all circular or oval, they all have twelve T-shaped pillars and two monolithic pillars, they all have a prepared floor. But the animals featured in the reliefs are different, suggesting to Schmidt and colleagues that they may represent people from different settlements who all shared the use of Gobekli Tepe. Certainly, the construction project would have required a sustained labor force to quarry, work and place the stones.
In a 2004 paper, Joris Peters and Klaus Schmidt argued that the animal images might be clues to the location of their makers. Structure A has zoomorphic reliefs dominated by snakes, aurochs, fox, crane and wild sheep: all but the sheep were known as important economically to Syrian sites of Jerf el Ahmar, Tell Mureybet and Tell Cheikh Hassan. Structure B has mostly foxes, which were important to the northern Fertile Crescent, but are also still found throughout the region. Structure C is dominated by wild boar images, suggesting the makers might have come from the central Anti-Taurus to the north, where wild boar are generally found. At Structure D, fox and snake dominate, but there are also crane, aurochs, gazelle, and ass; could this be a reference to water courses along the Euphrates and Tigris rivers?
Eventually, the oval structures at Göbekli Tepe were abandoned and purposely filled-in with refuse, and a new set of rectangular enclosures were built, not as well made, and with smaller pillars. It's interesting to speculate about what might have occurred to cause that.
One thing to remember about Göbekli Tepe's architecture is that it was constructed by hunter-gatherers, ancestors by a few generations of the people who would invent farming. Several of their residential settlements have been discovered along the Euphrates river not far from Gobekli. Food remains from Göbekli and other sites in the vicinity suggest they ate pistachios, almonds, peas, wild barley, wild einkorn wheat and lentils; and fox, asiatic wild ass, wild boar, aurochs, goitered gazelle, wild sheep, and Cape hare. The descendants of the makers of Göbekli would domesticate many of these animals and plants.
Göbekli's importance is as the earliest human-built cult structures in the world, and I'm eagerly waiting to see what the next decades of research shows us.
An Alternative Viewpoint
See the terrific discussion in Current Anthropology, written by E.B. Banning, and a raft of scholars who responded to his article.
Banning EB. 2011. So Fair a House: Göbekli Tepe and the Identification of Temples in the Pre-Pottery Neolithic of the Near East. Current Anthropology 52(5):619-660. Commentary from Peter Akkermans, Douglas Baird, Nigel Goring-Morris and Anna Belfer-Cohen, Harald Hauptmann, Ian Hodder, Ian Kuijt, Lynn Meskell, Mehmet Özdogan, Michael Rosenberg, Marc Verhoeven and a reply from Banning.