There are various hypotheses as to the origin of prokaryotic and eukaryotic cells. Because all cells are similar in nature, it is thought that all cells came from a common ancestor cell called the last universal common ancestor or LUCA. The LUCAs evolved into three different cell types, each representing a domain in the modern system of classification. The three domains are the Archaea, the Bacteria, and the Eukarya. We know that all three domains are cellular in nature, but they have one other feature in common. And this second common feature helped provide the biochemical evidence to support this newest step in classification. Cite the evidence utilized in this classification scheme.