The idea of evolution can be seen in early writings in ancient classical times and in the Islamic glory years. But these were rather speculative and not what we now would call 'scientific'. Instead, it was far more obvious and natural to think of creation as static. That is, one of the important concepts of pre-evolutionary thought was permanence.
Permanence didn't mean that nothing ever changes. After all, planets move. But motion isn't the same as coming into existence anew. The problem was that God has purportedly created 'the' universe, as such, reflecting His glory in our lives. Likewise, animals and plants move and are produced, but not out of thin air, only as offspring of existing members of their kind. What was seen as not changing were the types of animals and plants--species, and the specific objects in the cosmos. These were permanent, it was widely believed, because God made it so.
Evolution suggested that basic things came into existence on their own, as it were. If that were so, then God's work would be harder to understand, or so it would seem given the biblical literalist view of things before the age of science, even into the 19th century.
The point is that 'evolution' was a threatening idea not just to the world of biology in relation to Darwin's and Wallace's work, but more generally. Or, more generally, Darwin's and Wallace's ideas flopped down amidst what was already a controversial area. This can be seen in an interesting way in an area of science that otherwise might not seem to be threatening in this way......except that "In the beginning, God created the heavens and the earth".
19th century astronomy
Astronomy is more than just star-gazing in awe of Nature's wonders. It is about the cosmos, existence itself. It was long comforting, and pretty well consistent with known facts, to think of the cosmos as centered around the Earth, with the revolving Sun to warm us, and the Music of the Spheres, the stars painted onto crystal spheres, rotating more distantly around the skies.
Galileo's use of the telescope, and work of others tracking planets (mainly, Copernicus), had started to cast doubt on some of these ideas. The moon and planets weren't perfect spheres, and orbits weren't perfect circles and the Sun was the center of the solar system. Uncomfortable facts like these did shake religious orthodoxy (in the West, at least), but they really were mainly mathematical re-ordering of the same objects. More to the point, perhaps, and vital for Isaac Newton, was that the cosmos was orderly--specified by mathematic laws laid down by God (Galileo had had similar ideas). There was absolute location and time, in space, with things moving like clockwork, following the Laws.
One exciting way to study God's work was through telescopes, which had been getting better and better, by far, than what Galileo had to work with. A famous example is what became the largest telescope in the world in 1854 for nearly a century, in Ireland, affectionately called the Rosse Leviathan. (Rosse was one of the supporters and developers) A good discussion of this subject is the BBC Radio4 program, Science Stories, July 8, 2015 edition.
Here is an image of the Leviathan:
|The Rosse Leviathan, finished 1845|
Here are two images from modern telescopy, not the mid-1800s. Let's look at the top one first.
It was indeed a big smear in earlier telescopes, as if it were a cloud of gas. If that were the case, perhaps it was condensing into a star with the aid of gravity. And if that were the case, then the stars in the heavens were not fixed at all, but could come (and perhaps go)! And in turn, that would mean that the heavens themselves were not permanent: they evolved! And then what of Genesis and its like?
But what if it's just too far away, and only looks like a smeared cloud of gas? The new telescopes began to resolve some of these objects, and to show that, in fact, they were points of light--stars--so that, whew!, the Universe was static after all! Still other nebulae were too far to resolve in that way and the debate was about whether they were, in fact, even more distant stars, or were star-forming clouds.
Spiral formations, now known as galaxies, like the bottom image, were also thought perhaps to be swirls of gas that might be condensing, until they, too were resolved as stars. But this still left others too far to resolve, or truly gaseous condensations. Only in the 20th century did light spectrographs show that some of these were, indeed, gas clouds.
We now have a consistent understanding of these various phenomena, and no longer debate whether the universe is constant in the ways religious doctrine had taught. Nobody was exactly wrong. Swirling spirals can be galaxies, but dust can swirl in as gravity pulls it together in the formation of stars. The original appearances were ambiguous and the questions about what the clouds were were legitimate. The interesting aspect is the way in which the interpretation filtered through, and affected, the broader world-views about the nature of existence. And the relevance of this to biology is (and was) clear.
When all is ready
Exobiologists muse about life elsewhere in space and to date it's no more than musing, really. But real biologists, who study actual known life on earth, were discovering many facts about life in the mid-19th century that dovetailed with issues about cosmic constancy.
Even as far back as Aristotle's time, fossils of plants and animals were known. The knowledge was fragmentary and largely ignored rather than studied scientifically, but by Darwin's time two major aspects of change had become very clear. First was geological change, on land and regarding island chains. Erosion and mountain building were becoming clear as true phenomena. This may not really have changed religious feelings if the time periods were consistent with biblical events, like the great flood. But time was becoming more and more obviously far longer than what Genesis implied.
Fossils had more ominous import. Species that used to exist, had disappeared, and new species including modern ones appeared here and there. Georges Cuvier, a believer, suggested, reasonably, that these were events of catastrophic loss but new creation, as part of the Divine plan.
However ideas about biological change and evolution were beginning to swirl. It was one thing to know that agricultural species had changed (cows gave more milk, sheep had woolier wool, grain yields rose) because of active selection by breeders. It was not clear up unil then that new species had arisen (agricultural breeding never really produced new species). But the complex of worldwide data on plants and animals and their distribution, along with fossils and the idea (from agriculture and hobby breeding) that change could be brought about by selection, were forcing a realization that the living world, like the cosmos, might not be as static as dogma held it to be.
In a sense, 'evolution' was 'ready' to be discovered, here, there, and as a more general theme. Ideas about the evolution of society (e.g., Marxism, social Darwinism) were right there with the times, too. This intellectual foment in the new sciences undoubtedly contributed to the discoveries, eventually of the vastness of space and truly gaseous precursors of stars, and of biological evolution. The discussions 'in the air' set the stage. But at the same time, the ready resistance was also primed. That is why, I think, Darwinism hit such a brick wall of resistance from so many intellectuals at the time, and why so many found these ideas so deeply disturbing.
The context of history is important to the development of new ideas, but also to the reaction to them. Often, ideas in one area of life have impact, or perceived impact, on many others, including deep beliefs about the nature of things.
I think we've now mainly settled into complete comfort with the idea of biological evolution, with no longer any rational arguments against, even if peering into the microscopic nature of genomics still yields a picture as blurry in many ways as the Rosse scope's images. This is because many aspects of genetic causation remain subtle and elusive, because life seems not as rigidly law-like as physics. As to cosmology, visual telescopes were only the beginning of a technological odyssey that has shed light onto the origins and development of the universe and has led to general acceptance of the fact of change. But this hardly diminishes the truly mind-blowing matters, light and dark, that we are learning about, or now know that we still don't know about, regarding the size and scope of the universe(s).