Today's Google icon pays homage to Percival Lowell, the 19th century astronomer who popularized the notion that there were Martian-made canals on the surface of Mars and, therefore, Martians. The larger story surrounding his famous blunder discredits the idea that science moves inexorably forward, with never a major backward step.
Lowell, following the scientific consensus of his day, believed that Earth was unremarkable in the universe, and that since it was unremarkable, the rest of the solar system and universe must be teeming with intelligent life.
Astronomers now know that this assumption--called the Principle of Mediocrity--is false. Most immediately, Earth and the advanced life it holds are unique in the solar system. Whether there are alien civilizations in other parts of the universe is beyond the reach of contemporary science to determine, but already astrobiologists know that Earth is in fact a very unusual place in the galaxy, with a myriad of finely tuned conditions allowing us to exist and successfully practice many kinds of science.
Western scientists used to assume that Earth was unusual, but they got the geometry of it all wrong. After we got the geometry sorted out, conventional scientific wisdom took a step backward, discarding the correct conviction that Earth was, in some important sense, out of the ordinary. We've now had to go back and reclaim the view that Earth is unusual, even while appreciating how physically small the Earth is in relation to the vastness of the cosmos.
There are other examples of science moving backwards. Nineteenth and early twentieth century scientists generally assumed that the universe was eternal. For many, this meant that they needn't explain its origin. Discoveries by Edwin Hubble and Arno Penzias among others put an end to this view, returning us to an older position consistent with the Judeo-Christian view that the universe had a beginning.
A third example: Evolutionists leading up to and after Darwin assumed that life could generate spontaneously from non-life without much difficulty. This was based, in part, upon the idea that there wasn't a firm line of demarcation between life and non-life. We now know that moving from non-life to life is anything but simple, and that the demarcation between the two involves a quantum and discontinuous leap, a view consistent with an older view that the initiation of life on Earth demanded something extraordinarily special.
The motivations for these three missteps in the history of science are complex, but they have in common the fact that they each supported non-theistic worldviews. Each could be reconciled with theism, but each gave aid and comfort to atheism or deism. Darwinism is of a piece with these missteps. It gives aid and comfort to atheism and deism. And a growing body of scientific evidence suggests that it isn't the case.
The parallels can be extended further still. As with the Principle of Mediocrity, Darwinism contains a kernel of truth that persists, a kernel that its defenders frequently point to in defending the total theory against the charge of obsolescence. Those who defend the Principle of Mediocrity (Earth is unremarkable) point to the discovery of how physically small Earth is in relation to the vast sea of the cosmos. And Darwinists point to instances of non-controversial microevolution to defend the poorly supported view that all life evolved by random mutation and common descent from an original ancestor cell. Both Earth's relative smallness and microevolution are true, and both are insufficient to stem the growing tide of evidence against the larger models they are used to defend.
