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How did ribosomal RNA evidence change the classification of life?

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A herd of African elephants stands at the edge of the Chobe River in Botswana, drinking water with a backdrop of dry hills and scattered green trees. — life A herd of African elephants (*Loxodonta africana*) drinking from the Chobe River, Botswana.

The analysis of ribosomal RNA (rRNA) fundamentally transformed biological classification by shifting the focus from observable physical traits to phylogeny, or evolutionary history.1

In 1990, Carl Woese and his colleagues utilized rRNA sequences to establish the three-domain system of life. This system replaced the older five-kingdom model, which relied heavily on morphology and modes of nutrition. The rRNA evidence revealed that life is divided into three distinct evolutionary groups:1
* Bacteria
* Archaea
* Eukarya

This research demonstrated that Archaea and Bacteria are as genetically distinct from each other as they are from eukaryotes, suggesting they diverged from a common precursor long before eukaryotic cells evolved. Furthermore, rRNA analysis has exposed the limitations of relying on phenotypic traits for classification, as organisms that appear physically similar may be genetically distant, and vice versa. By providing a quantitative, molecular basis for assessing relatedness, rRNA evidence has allowed scientists to map the deep evolutionary relationships of life on Earth with greater accuracy.23