Here's why:
* DNA is the blueprint of life: It contains the genetic code that determines an organism's traits.
* Mutations accumulate over time: As organisms evolve, changes (mutations) occur in their DNA sequences. The more similar the DNA sequences between two organisms, the more recently they shared a common ancestor.
* Closely related organisms share more similarities: Organisms that are closely related have a more recent common ancestor, so they have had less time to accumulate differences in their DNA.
Other factors that can be used to infer relatedness include:
* Protein sequences: Proteins are made based on the instructions in DNA. Similar protein sequences suggest a closer relationship.
* Fossil evidence: The fossil record can show how organisms have changed over time, providing clues about their evolutionary history.
* Anatomical similarities: Organisms that share similar body structures are more likely to be related.
However, DNA sequences provide the most direct and reliable evidence for determining evolutionary relationships.
