To be specific, it doesn't mean that truth morphs through time, but rather our understanding of truth morphs through time.
Lets face it, our understanding of physics and almost all other sciences is derived from our limited perception of the world around us.... Lack of understanding, and misconception will stay there forever; yet, truth always stands out from the crowd! Not necessarily quickly, but it eventually will.... Our perception of the world around us will be put to trial on every occasion we try to apply our theories about the world around us; The misconceptions will fail to explain the phenomenons that we observe!
We all know the old "spontaneous generation" theory that suggested that:
According to Aristotle it was a readily observable truth that aphids arise from the dew which falls on plants, fleas from putrid matter, mice from dirty hay, and so forth. (source)
In accordance to the perception of those people, it was obvious that 'spontaneous generation' does happen... But as we always know, "mutations" will come in the way!
New mutant ideologies did evolve and competed for survival against the prevailing 'spontaneous generation' ideology... At that time, truth (maybe not complete truth, but merely a better perception) was nothing more than very few mutants; A similar example is how the spherical earth thesis, has been long time ago challenged by the flat earth thesis!! But truth is always way much solid than falsehood; Perception of Truth evolved! We now know better....
Not all lies are equally "bad"; the really bad ones are eliminated first; the more serious and obvious a falsehood is, the sooner it will go away; that's natural!! You cant jump up ladders, you go one step at a time. In other words, 'spontaneous generation' was a weakly supported perception of the world, so it got way before than the theory of "atomism" (Greek word atomos which means "that which cannot be cut into smaller pieces"), as atoms were not as easily observable as living organisms are.
Much like in the animal kingdom, no animal is invincible (ie. we don't have perfect perception of our world), but there are always the strong, the stronger, and the weak!! Once the weak ones are out, a new series of competition will take place between the remaining strong ones, and so forth forever!
In this context, i bet you that a D-student in our time, can easily out-smart an A+-student in 1000 BC; and an A+-student of our time, is such a big failure against a D-student in 3000 AC!
In this series:
Darwinistic Evolution Of Truth: Part 1 - Introduction
Darwinistic Evolution Of Truth: Part 2 - Religious Wars
Darwinistic Evolution Of Truth: Part 3 - The Importance Of Liberal Thought