The Taguans evolved sentience approximately two billion years ago. Their ancient history was a highly sought after archeological topic, as the Taguan government allowed only 974 expeditions in the past 22,000 years. In recent history, however, the Taguans have allowed the Vulcans to examine the site several times, but the Taguans sealed off their planet to foreign visitors in the mid-23rd century. (TNG: "Qpid")
In the novel Q-Space, Q takes Captain Jean-Luc Picard into the distant past of Tagus III, where he witnesses the Imotru, the previous sentient inhabitants of Tagus – the Taguans of the present are apparently a later evolution of life on their world – during a local ceremony where a group of Imotru glide for over two days and proceed to sky-dive into a ring of fire to evade man-eating sea snakes, Q noting that he enjoyed witnessing the rite in his youth as it reflected how lower beings were unafraid to take chances and refused to accept limitations.