Natural historians loved to categorize living things. Aristotle was a great observer, he is credited with creating the “scientific method”. He carried out some of the first empirical studies. He categorized living things into 3 categories and within these categories “like mates with like”:
- Plants – vegetative soul which allows them grow
- Animal – sensitive soul which allows them to move
- Humans – rational soul which allows them to reason
Carl Linnaeus took categorization to a whole new level. He made a binomial naming system that categorized minerals, plants, and animals into several different groups from Kingdom to species. He was the first natural historian to put humans in the primate order, suggesting humans were a part of nature rather than gods creation – which was very controversial for the time – and he was the first to correctly identify bats as mammals.
But many of these ancient naturalists believed that everything was static -no evolution.
But in the 18 century things started to turn around – naturalists turned scientists, there were big discoveries in astronomy, physics, chemistry, and geology. This was the time that European scientists observed that life was not static.
Georges-Louis Leclerc, Compte de Buffon thought species were “de-evolving” or degenerating – getting worse than how god initially designed them. He rejected the idea that species evolve into other species but rather that species change due to random chance or the environment over time. This is more along the lines of micro-de-evolution. He believed that he lived in the “Old World” while the Americas were the evolved “New World” and their animals and people were smaller and weaker.
“No American animal can be compared with the elephant, the rhinoceros, the hippopotamus, the dromedary, the camelopard [giraffe], the buffalo, the lion, the tiger…” (Volume 5 of Histoire naturelle)
He was also against Carl Linnaeus’ the idea that apes and humans shared a common ancestor. But there is some good that came from his ideas. Geologists started to uncover fossils and rock layers that clearly showed an aging planet. While in the 1600’s Bishop James Ussher predicted the world to be 6000 years old after reading the bible, Compte de Buffon believed the world to be 75 000 years old…in public (in private he believed it to be 10 million years old, but he didn’t want all the controversial hate so he kept his public opinion conservative). Now Compte de Buffon was still a religious man, and to appease to his colleagues’ beliefs he described the Genesis as more of a metaphor: God didn’t create the world in 7 days, he took thousands of years, and on the 6th day – or several thousands of years later – he created humans. This idea, suggested humans came after nature, which was controversial in itself.
The first brave man to voice his hypothesis of evolution was Jean-Baptiste Lamarck. However, he didn’t get it exactly correct. He believed that all species were striving for perfection and complexity, that species would gain or lose organs as a result of their use or disuses, respectively, and that changes can happen during a lifetime and be passed on to the next generation. First, evolution does not have a goal, if every species we see was striving for complexity then those house flies you swat would have figured out a way to get their revenge by now. Second, we have vestigial traits. These are traits that we no longer use but still stick around, for example wisdom teeth or tail bones. Thirdly, evolution takes a lot of time and you cannot pass on changes that you’ve acquired in your lifetime to your descendants. For example, I used to have very bad myopia (almost -6.0 for both eyes), but I got laser eye surgery to correct my vision. Going by Lamarcks hypothesis, my children would have perfect vision, since I’ve corrected mine. This of course is not the case.
Many other scientists did not accept Lamarck theory. Specifically because his third hypothesis (that changes happen in a lifetime and get passed on) was easily observable to be false. Some scientists gave the evidence of bowed legs – people who rode horses often would have bowed legs, but their children were born with normal legs.
George Cuvier was one of these people who rejected Lamarcks idea, but he still believed in earlier life forms, extinction, and dinosaurs. Cuvier believed each species is adapted to its environment, but that species don’t necessarily change over time. Instead, Cuvier believed that the planet goes through major catastrophes (major floods, volcanic eruptions) that wipe out creatures and new ones just restart. Cuvier was an expert on dinosaurs and would see that specific layers would hold particular species and that these species were wiped out by particular catastrophes, hence why we no longer have dinosaurs.
On the opposite spectrum, we have Charles Lyell, who was against the catastrophism idea and instead believed in James Hutton’s Uniformitarianism idea – the planet goes through observable geological changes balanced across time. So much less dramatic and moderate change of the earths surface than catastrophism. Lyell believed the earth changes slowly and progressively and so do the species on it. And then Lyell read Darwin’s work.
In 1858 Alfred Russel Wallace and Charles Darwin, independently proposed a [now] theory: evolution by natural selection. Alfred Russel Wallace was a contrarian from a modest background . He believed that changes in living things would lead to speciation. These changes by Wallace’s predictions were caused by the environment only (rather than sexual selection as Darwin would later predict). Wallace believed these changes arose as soon as the environment experienced a change, like a feedback mechanism rather than directional selection.
Darwin, on the other hand, proposed the theory of natural selection which included sexual selection. He predicted that species preserve and accumulate small advantageous changes as a population. Species would compete to survive and reproduce and change to gain an advantage in either or both of these goals. This process is also very slow, Darwin predicted:
“Natural selection acts only by taking advantage of slight successive variations; she can never take a great and sudden leap, but must advance by short and sure, though slow steps.” (Charles Darwin, “On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life,” 1859, p. 162.)
Darwin and Wallace helped each other to cement the idea of evolution by natural selection. Wallace had collected small pieces of evidence from insects around where he lived, while Darwin had the money to travel around collecting evidence of macroevolution – the evolution of different species. Darwin observed how the finches in the Galapagos were all different depending on which island they lived and their diet. He also found how females would choose males over other, less attractive, males.
There was one animal that did confused Darwin. The caterpillar. Why were caterpillars such bright colours? Surely, being so bright was against natural selection; you’d be easily spotted by prey and it did not seem like females preferred specific colouration. This is why working together is important! Wallace explained to Darwin, that the bright colouration was a form of natural selection as it was a signal to their prey: “Hey I taste and smell really bad”, so birds, or other prey, would avoid these caterpillars. I’m not exactly sure how Wallace found out caterpillars taste bad, but since I remember Darwin put a beetle in his mouth one time, I wouldn’t doubt Wallace may have done the same with a caterpillar.
Now that you understand the history of evolution feel free to read up on my simplified explanation of evolution and sexual selection. I am also very excited to share that I got the opportunity to chat with Occultae Veritatis – one of my favourite podcasts – on Creationism vs Evolution (if you don’t want to listen in a web browser you can find this podcast on Spotify, iTunes, or wherever else you get your podcast).