Here's why:
* DNA as a universal code: The use of DNA as the primary carrier of genetic information across all living things points to a shared origin. It's like finding the same blueprint used to build different houses, suggesting they were all designed by the same architect.
* Similarities in DNA structure and function: Not only do all organisms use DNA, but the structure of DNA and the way it functions (replication, transcription, translation) is remarkably similar across all life forms. This consistency further strengthens the argument for common ancestry.
* Evolutionary relationships: By comparing DNA sequences between different organisms, we can trace evolutionary relationships and see how species have diverged over time. These comparisons consistently show that all life forms are connected through a shared evolutionary history.
While there are some variations in the specific genetic code (e.g., mitochondrial DNA has a slightly different code), the underlying principles and the overall structure of DNA remain remarkably consistent across all life.
