In a previous post, you learned that evolution is a theory, and a theory is something that all the scientific evidence supports. In another post, you learned about the theory of evolution. But, how did the theory of evolution come about? What was the evolution of evolutionary thought? Well, in order for the theory of evolution to be developed, some ideas needed to change.
In the first post in this series, we looked at ideas about the relationship between humans and other forms of life. In the second post, we looked at ideas about the age of the Earth. Then, in the last post, we looked at ideas about fossils and what they implied about life. Now, we will continue our study of evolutionary thought by exploring adaptation to the environment. People’s ideas about adaptation needed to be changed in order for the theory of evolution to be developed.
The OLD IDEA was: God made each form of life perfectly adapted to their environment.
The NEW IDEA was: Organisms vary in their adaptation to the environment.
Back before the theory of evolution was developed, people got all their answers from the Christian Bible. According to the Bible, all living animals started out together, in the mountains of Ararat, where Noah’s Ark landed after the great flood. And all animals were perfectly adapted to their environment because God made them like that.
But, the animals were not adapted to the mountains of Ararat, so how did all of the polar bears make it to the Arctic, and all of the koalas get to Australia, and how did all the lemurs get to Madagascar? People needed an explanation for adaptation.
Jean-Baptiste Lamarck came up with an idea that when the environment changes, an organism will also change to fit the new environment. He thought that the organism somehow recognizes that the environment has changed, and then it adapts. Lamarck said that “fluids and forces” would be sent to a particular body part and it would be modified to work better with the new environment. New organs could even be formed as well. And, the new trait would be passed down to their offspring. This theory is called the inheritance of acquired characteristics.
Here’s a famous example of Lamarck’s theory. Say there is a giraffe, and he ate all the leaves on the lower branches of a tree. He then tries to reach the upper branches, and fluids and forces move to the neck tissues and make the neck slightly longer, so the giraffe can reach higher. Then, the longer neck is passed down to the giraffe’s offspring. And, over time, all the giraffes will have longer necks than before.
Well, Lamarck’s theory is not true. First of all, an organism can’t just create new organs or modify body parts just by wanting to do it. And second, a trait that is acquired during life cannot be passed down to your children. For example, if a man loses an arm in a car accident, his babies will not be born missing an arm.
Then, in 1798 Thomas Malthus created a theory about organisms and their environment. He thought that more offspring are born than can survive in any given environment, because the population grows bigger and bigger but the amount of food and water stays about the same. This would create competition for the few resources available.
Now, in steps Charles Darwin. We’ll learn about his ideas in the next post, but he integrates all the previous ideas I discussed into his theory of natural selection—that humans are related to animals, that the Earth is very old, that organisms change over time, and that organisms adapt to an environment in which there is competition for resources.
In summary, people believed that all organisms were made by God to be adapted perfectly to their environment. But evidence was growing that this wasn’t the case. Jean-Baptiste Lamarck came up with the idea that organisms could modify themselves in response to the environment, and then pass that characteristic down to their offspring. This was called the inheritance of acquired characteristics, but it was incorrect. Thomas Malthus came up with the idea that organisms compete for resources in their environment. And now, Charles Darwin enters the picture. In the next post, we’ll explore his ideas, and how he integrated all the previous ideas that I discussed.
Want to learn more about evolution?
Just take my Udemy course, “Exploring Genetics and Evolution Through Physical Anthropology: Anthropology 4U” at this link.
Thanks for reading!