The theory of evolution by natural selection is now widely accepted. When Darwin proposed it there was not enough evidence to convince many scientists, but data is now available to support it.
One piece of evidence is that we now know characteristics are passed on to offspring in genes. This was the missing mechanism of inheritance in Darwin's time. It explains how the characteristics that help individuals to survive are passed on to the next generation.
A second piece of evidence is the fossil record. Fossils show how organisms have changed over millions of years, and they can be used to compare organisms from different times in the past with those alive today.
A third piece of evidence is antibiotic resistance in bacteria. Bacteria reproduce very quickly, so they can evolve rapidly. A mutation can make a bacterium resistant to an antibiotic. When the antibiotic is used, the resistant bacteria survive and reproduce, and the non-resistant ones are killed. The resistant strain becomes more common. This is natural selection that can be seen happening in a short time.
