The Synthetic Ascension Path focuses on abandoning your frail biological forms for that of a perfect machine. The first step, the Flesh is Weak, requires the Droids technology and allows you to modify your entire population through a special project, turning them into cyborgs. This gives them an immediate +20% boost to habitability, as well as bonuses to mineral production and army damage, and also makes any leaders generated from those species have the Cyborg trait granting an additional +40 years of lifespan.
The next step, Synthetic Evolution, requires the ability to build Synths, and allows you to upgrade your cyborg population into fully mechanical forms, finally abandoning the frailty of flesh for the surety of synthetics. When it is complete, you will become a fully robotic empire, with a robotic primary species. Your population will benefit from all the advantages normally conferred to Synths in production and research, and all your leaders will be immortal, able to be killed only in battle or through events. You will also naturally no longer require Food for your synthetic population, instead being replaced by an Energy maintenance similar to regular Synths. You will also be able to name your new, gloriously post-biological people.