We know, DNA is the main molecule by which scientists can learn about evolution by comparing the DNA structure between two different organisms.
But, in addition to DNA (which is most helpful & important) still, there are 3 molecules that can help us, They are:
1) RNA : - It is found in cytoplasm, as DNA transfers it's codes into RNA during Central dogma, it can help us in evolution studies.
2) Proteins: - Another helpful feature, into which RNA transforms in Central Dogma.
3) Pseudogenes: - It is also known as "Non-coding DNA" It is extra DNA in a genome that do not get transcribed into RNA to synthesize proteins. They can also help us in Evolutionary studies.
Hope this helps!