Retrogression (Noun)

Returning to a former state.

Nouns denoting acts or actions.

The country's economic growth has suffered a retrogression to its pre-recession levels after years of stagnant growth.
After her surgery, she experienced a retrogression to her old self, regaining her youthful energy and vitality.
The government's policies led to a retrogression in environmental conservation efforts, undermining decades of progress.
His recovery was hampered by a retrogression of his physical condition, forcing him to restart his rehabilitation from the beginning.
The politician's approval ratings underwent a retrogression after a series of scandals tarnished his public image.

Passing from a more complex to a simpler biological form.

Nouns denoting natural events.

The dinosaur's legs displayed a retrogression from the typical quadrupedal stance of its ancestors, instead opting for bipedalism.
The species of ancient horses showed a clear retrogression in the number of toes, with the modern horses having only one functional toe.
In the fossil record, paleontologists observed a retrogression in the brain size of certain early human ancestors, contrasting with the more advanced cerebral features of modern humans.
The retrogression of the birds' teeth, from a complex dental arrangement in theropod dinosaurs to the simplified beaks of modern birds, highlighted the key adaptations that occurred during avian evolution.
The gradual retrogression of the limbs of whale ancestors, from terrestrial mammals to marine mammals, illustrates the dramatic transformation that occurred as these animals adapted to aquatic life.