The simplest way to validate the natural law of evolution is based on the universal human experience in which all of us know that we are in a continuous state of becoming. This is not a function of belief, or needing to believe it. It is simply a fact.
Of course, any of us can observe the natural law of evolution in countless ways as applied to the totality of the Creation. We can observe it relative to the evolution of the human life form. We can observe it in the life of plants and animals. We can observe it through the fundamental changes over great lengths of time to the Earth itself as a evolving planet. We can observe it through our telescopes pointed out into the universes. We can observe it even at a molecular level of life.
Evolution simply comes down to, and means, the changing of form, the changing of structure, the changing of energy, and the change of anything. The very word change implies evolution.
Evolution is always proceeded by another natural law called involution. What this means is that for a change or evolution to occur, relative to some structure, form, energy pattern, dynamics, etc., it is always proceeded by an involution, which simply means the ending or destruction of something that pre-exists.
That which pre-exists, when evolution or change becomes necessary, implies and means that some pre-existing something, a dynamic, structure and so on, is promoting a state of stagnation or non-growth. In all life forms, in anything that exists as phenomena within the totality of the Creation, there exists another natural law called survival. When this natural law is ignited or stimulated, for whatever reasons, it will always cause the natural law of involution, leading to evolution, to occur, so that the ongoing survival of a life form, structure, and so on can occur.
The natural laws of evolution and involution have two ways of manifesting. One way manifests as a slow, progressive, non-cataclysmic process of change. Darwin called this the natural law of uniformity. And the the other way, of course, is cataclysmic change, in which the very nature of the process of involution leading to evolution is intense and very abrupt.
This is very different than the evolution reflected in the natural law of uniformity, which allows for a gradual change over time. Cataclysmic evolution creates a sudden change that is immediate and stark.
Again, these two natural ways of evolution are observable by anyone as facts that do not require any belief at all. The natural law of evolution and involution correlates astrologically to Pluto.