This coming Saturday is Darwin Day, but who was he and why does everyone think he is so important? Mary Mulvihill looks back on some of his great discoveries and achievements.
There are not many scientists whose birthday is celebrated every year by devotees around the world, but Charles Darwin was no ordinary scientist.
Among other things, he was the first to explain how coral atolls form, the first to discover that some plants eat insects, that earthworms recycle the organic matter in soil, that many flowers possess intricate mechanisms to ensure they are cross-fertilised by other plants (and not by their own pollen), that such cross-breeding produces healthier offspring than inbreeding does, that species diversity is crucial for a healthy ecosystem, and that barnacles are an amazingly diverse bunch. Oh, and he also came up with a theory that would profoundly change our view of the world and our place in it.
The idea that species could evolve had been around for perhaps two centuries. A few people, including even some creationists, happily accepted it. But Darwin's view of evolution, driven by natural selection and resulting in "descent with modification", was the first to do away with the need for a Creator, and to place humans firmly among the animals. Not surprisingly, when On the Origin of Species by Means of Natural Selection was first published in 1859 it rocked the establishment.
Where others looked at nature and saw evidence for an intelligent designer or a benevolent Creator, Darwin saw instead order, the struggle to survive, and the mindless, relentless action of the laws of nature.
The core of his theory was simple: if chance variation gives an individual some advantage over its neighbours - a slightly better eye, for instance - then that individual is more likely to survive and pass the advantage to the next generation. Run this simple algorithm over countless generations, and eventually populations will diverge, new species emerge and some old species disappear.
It was a daring proposition, yet Darwin was not a daring man. Though he began working on his species ideas in 1836, after a five-year voyage of discovery on HMS Beagle, he kept it secret, telling his closest friend only in 1844 and leaving money for his wife to publish the manuscript in the event of his death. He was also struck by bouts of vomiting, dizziness and fatigue that would plague him the rest of his life; this may have been partly caused by a tropical disease picked up on his travels, but more probably by stress and anxiety, for Darwin could see where his work was taking him. And in the end, he was pressed into publishing only when Alfred Wallace came up with a similar theory.
It is no surprise that two naturalists developed the concept of natural selection, because all the evidence was accumulating. Naturalists were discovering millions of previously unknown species, including microscopic marine organisms never before dreamed of; expeditions meant naturalists could observe species in their native habitat; fossils of extinct species such as dinosaurs were unearthed, and of other creatures, such as a giant sloth, that was clearly similar to living modern-day species.
Geologists also discovered that the planet itself was evolving, under the gradual action of forces such as erosion. The world had therefore been in existence far longer than the Biblical 4,000 years, and possibly for millions if not billions of years. And since Copernicus and Galileo had removed the Earth from the centre of the Universe, the way was open to push humans off the top of Creation.
Darwin found further evidence in domestication and even the breeding of fancy pigeons; in similarities between his infant children and Jenny, the first living orang-utan exhibited at London zoo in 1837; in the fact that humans and animals can succumb to the same diseases (e.g. flu).
His young daughter's agonising death from tuberculosis, the cruel struggle for existence, and even parasitic wasps that lay their eggs in the living bodies of other insects, convinced him that the world was not ruled by any benevolent being.
Darwin sees the bigger picture and the overall scheme of things and concludes: that all living creatures are ultimately related, and that humans and chimpanzees share a common ancestor. But this last was too much for many, including Alfred Wallace, who believed in divine intervention when it came to humans, an argument that continues today.