Final answer:
Genetic testing suggests that microbes most closely resemble the common ancestor of all life, with genetic tools revealing our deep genetic relationships. Humans share about 98% of their DNA with chimpanzees, but it is the microbial world that holds the key to our earliest evolutionary history.
Step-by-step explanation:
According to genetic testing, the organisms that most closely resemble the common ancestor of all life are typically microbial in nature. Genetics and genomics have played significant roles in unveiling the shared genetic code across various species.
Comparing gene sequences reveals the degree of relatedness among organisms and leads to the construction of the tree of life. In particular, studies on DNA similarities have determined that humans and chimpanzees, sharing about 98% of their genes, are closely related, indicating that they share a common ancestor that lived relatively recently in evolutionary terms.
However, the microbial world showcases even more profound similarities to the common ancestor, as microbial life represents a vast portion of Earth's biodiversity. Microbes exhibit incredible genetic diversity and have existed for billions of years, highlighting their closeness to the early forms of life on Earth.
In fact, recent discoveries have identified new branches on the tree of life through the genetic analysis of rare microbes, drawing us even closer to understanding our most ancient common ancestors.
The Last Universal Common Ancestor (LUCA) is another concept referring to the most recent organism from which all life on Earth descends. This supports the theory that the roots of the tree of life, include all three domains: Archaea, Bacteria, and Eukarya, converge on a single ancestral lineage.
Thus, our most similar genetic relatives are not only the great apes but also the vast and largely unexplored microbial realm.