The organism that is most similar to a human's DNA is the chimpanzee (Pan troglodytes). Studies have shown that humans and chimpanzees share approximately 98-99% of their DNA, making them our closest living relatives in the animal kingdom. This genetic similarity reinforces the idea of a shared evolutionary ancestor. The similarities extend beyond DNA; chimpanzees exhibit complex social behaviors, tool use, and emotional expressions akin to those of humans. This has made them subjects of extensive scientific research, contributing to our understanding of genetics, evolution, and the nature of intelligence.