The idea of evolution has changed a lot over time. Different scientists and cultures have shaped how we understand it. Here’s a simple look at the history of these ideas:

Early Ideas

1. Before Darwin: Before Charles Darwin came along, many people believed in creationism, which is the idea that life was created by a higher power. Philosophers like Aristotle talked about a "scala naturae," which means a sort of ladder showing how different living things are ranked.
2. Lamarck's Theory (1809): Jean-Baptiste Lamarck had a unique idea. He believed that animals and plants changed to fit their environment. For example, he thought that if an animal used a part of its body a lot, it would get stronger, and that trait could be passed down to its kids. But many people didn’t agree with him, and he didn't have strong evidence to back it up.

Darwin and Natural Selection

1. Darwin's Trip (1831-1836): Charles Darwin took a long journey on a ship called the HMS Beagle. During his trip, especially at the Galápagos Islands, he noticed many differences among animals. He saw how species changed to survive in their own environments.
2. "On the Origin of Species" (1859): Darwin wrote a book where he explained natural selection. He believed that animals and plants that had helpful traits would survive better and have more offspring. He outlined some key ideas:
   • Variation: Every individual in a group of the same species is a bit different.
   • Inheritance: These differences can be passed on to their children.
   • Survival of the Fittest: The individuals that are better suited to their surroundings tend to survive longer.

Modern Understanding of Evolution

1. Mendel's Genetics (1900): In 1900, scientists rediscovered the work of Gregor Mendel, who studied how traits are inherited. His findings helped connect genetics with evolution.
2. Modern Synthesis (1930s-1940s): This period brought together Darwin’s ideas with Mendel’s genetics, which helped people understand evolution better. Now, it is seen as changes in the traits of a population over time.

What We Know Today

1. Population Genetics: We often look at evolution through the lens of population genetics. The Hardy-Weinberg principle is an important idea here. It says that allele frequencies in a population stay the same under certain conditions, which can be written as: $p^2 + 2pq + q^2 = 1$ In this, $p$ and $q$ are used to show the frequencies of two different forms of a gene.
2. Molecular Evolution: New technologies in DNA sequencing have helped us understand how genetic changes happen in evolution. It shows the importance of mutations in these changes.

In conclusion, the idea of evolution has grown a lot from its early ideas to a strong scientific explanation. It is now backed by plenty of evidence from different areas of biology.