Every organism alive today is equally 'evolved,' with no hierarchy of advancement

Dawkins uses the pilgrimage structure to dismantle a persistent popular misconception: the idea that evolution is a ladder of progress with simple organisms like bacteria at the bottom and complex ones like humans at the top. Since every currently living species has survived an unbroken chain of successful reproduction stretching back to life's origin, all of them are equally 'successful' products of the same span of evolutionary time, whether that lineage happens to be structurally simple or complex. A bacterium alive today is not a primitive leftover on the way to becoming something else; it is the current endpoint of billions of years of its own continuous adaptation, just as much as humans are the current endpoint of their lineage. Dawkins argues this reframing matters because the ladder metaphor smuggles in an unwarranted value judgment, treating complexity or resemblance to humans as the measure of evolutionary success, when natural selection has no such built-in goal or direction, only differential survival and reproduction in whatever environment a lineage happens to occupy.

Takeaway: a bacterium isn't 'less evolved' than a human, it's equally many billions of years down its own unbroken evolutionary path.