Final answer:
Humans share 99.9% of DNA with each other due to our shared ancestry and evolutionary processes, with the remaining 0.1% accounting for individual differences.
Step-by-step explanation:
Humans share 99.9% of our DNA with each other due to our close relatedness as a species. This high level of similarity is indicative of shared ancestry and is an outcome of the evolutionary process. Within a species, there is a high degree of genetic similarity because individuals have descended from common ancestors, and this genetic blueprint is responsible for the development of shared characteristics that are crucial for reproductive success. Comparative genomic studies have shown that we share nearly 98% of our genes with chimpanzees, our closest living relatives. This points to a common ancestor between humans and chimpanzees in evolutionary history. Such analyses provide key insights into the interconnectedness of all life on Earth and the evolutionary relationships among different species. The variation that does exist, the 0.1% of our DNA, accounts for individual differences, including susceptibility to diseases and responses to medications. Studying these genetic differences known as Single Nucleotide Polymorphisms (SNPs) is challenging but crucial for understanding the genetic basis of diseases and developing personalized medical treatments tailored to individual genetic profiles.