Natural selection is just three factors - over-production, variation, and inheritance combined to produce adaptation to changing local environments. It's not a principle or progress; it's just a principle of local adaptation. You don't make better creatures in any cosmic sense; you make creatures that are better suited to the changing climates of their local habitats.

Change is more often a rapid transition between two stable states than a continuous transformation at slow and steady rates. . . .Change occurs in large leaps following a slow accumulation of stress that a system resists until it reaches the breaking point. Heat water, and it eventually boils. Oppress the workers more and more and bring on the revolution.

I emphatically do not assert the general 'truth' of this philosophy of punctuational change. Any attempt to support the exclusive validity of such a grandiose notion would border on the nonsensical.

The extreme rarity of transitional forms in the fossil record persists as a trade secret of Paleontology. Evolutionary trees that adorn our textbooks have data only at the tips and nodes of their branches; the rest is inference, however reasonable, not the evidence of fossils.

Charles Darwin viewed the fossil record more as an embarrassment than as an aid to his theory.

Is uniformitarianism necessary?

The history of life is more adequately represented by a picture of 'punctuated equilibria' than by the notion of phyletic gradualism. The history of evolution is not one of stately unfolding, but a story of homeostatic equilibria, disturbed only 'rarely' (i.e. rather often in the fullness of time) by rapid and episodic events of speciation.