Star Trek: 10 Things You Didn’t Know About Dax

You may get the impression that Trill symbionts spend their whole lives joined with humanoid Trills, but it's actually more complicated than that.

The Dax symbiont was born in 2018 and lived for 150 years before finally being joined with their first host, Lela, in 2168 (shortly after the time period of Star Trek: Enterprise).

Not much is known about these early years of the symbiont's life. We know that unjoined symbionts are bred in pools on the Trill homeworld, where they reside under the protection of the Trill Guardians until being joined. The symbionts could communicate with each other using electrical pulses in these pools, so it's likely the first century-and-a-half of Dax's life was spent learning all they could from fellow symbionts before transitioning to life as a humanoid.

Trill symbionts can usually live for several centuries, so, for them, their first 150 years are like their childhood.