The world we live in was a very different place millions of years ago. Most of the organisms we know now did not exist. Instead, dinosaurs lived all over the Earth. We know this from fossil records. So what happened, how did humans come to rule the Earth if we didn’t even exist 16 million years ago? Well, evolution is the answer.
Charles Darwin came up with the idea of evolution through natural selection in the 1800's while sailing from Africa, around the bottom of South America and up the Galapagos Islands. When he published his findings there was an outcry, and not surprisingly so! This was quite a radical idea at the time and scientists had many questions. How could something as complicated as the eye evolve from natural selection only? What evidence supported this hypothesis?
This was a real problem for Darwin as he really believed in his hypothesis and he had some evidence. For example, he knew that finches had adapted to live on one specific island only. But he was missing a big piece of the puzzle, and these missing pieces were fossils.
Fossils are the imprints of dead plants and animals that turned into stone over millions of years. Some species, like the horse, have changed significantly over time and we know this because we have a complete fossil record of the horse. This is called evolution. We do not have fossil records for all organisms. For example, we don’t have a complete fossil record for humans.
After Darwin died, people started to show that his hypothesis was correct by finding evidence from the fossil record of different animals. As more and more evidence started to build up, more and more people believed in his hypothesis until, one day, there was so much evidence that this could be the only explanation and Darwin’s hypothesis became a theory.
Today, we have DNA evidence as well, showing us that animals are related to other animals that look similar. DNA provides another piece of evidence which makes the theory of evolution irrefutable, meaning that we have so much evidence to support the theory that it has to be correct.
Finally, the real breakthrough came when we observed evolution in action. Normally, it takes millions of years for organisms to evolve, but it only takes bacteria a short time. We now have a branch of bacteria called MRSA that didn’t exist 60 years ago. It has evolved to deal with the use of antibiotics (chemicals that kill bacteria) and it is now immune to most of our antibiotics.
Let's explore evolution in more depth by going through some questions.