↣ Fixism vs evolution

Nowadays, we know that living things evolved and diversified from the first living organisms. However, until the late 19th century most scientists believed in the theory of fixism. 

Although there were several different theories of fixism, they all stated that living things do not change and therefore species always stay the same. They believed that the species that we see on the Earth today are the same as the original species. 

However, in ancient times people had already found fossils. The fossils showed different living things to those they could see, so they realised they must have come from other organisms that inhabited the planet sometime before them. 

At the end of the 18th century, Georges Cuvier developed one of the most logical theories of fixism. When Cuvier was studying fossils in sedimentary rocks, he observed that most of them came from living things that had become extinct. He also realised that they were different to the living things that he could see around him. 

To explain this discovery, he argued that there must have been several catastrophic events followed by periods of creation in the history of our planet. Therefore, species were created and existed for a period of time before being destroyed by great natural disasters. 

Cuvier calculated that the great flood described in the Bible had been the last natural disaster, which explained the presence of marine fossils in the interior of continents. 

This meant that the living things they could see had been created in the last period of creation or they had managed to survive previous natural disasters. 

Fixism theories started to be questioned at the beginning of the 19th century, when the first evolutionary ideas appeared. However, fixism was not ruled out definitively for many years because of the following reasons: 

↦ Evolutionary processes are slow and cannot be observed in one human life. 

↦ There was no understanding of genetics, so it was difficult to understand how new characteristics appear and can change a species into a new one. 

↦ In those times, defending an evolutionary theory meant confronting religious doctrines.