Final answer:
To document the MRCA, scientists use techniques combining morphological evidence from fossils with molecular evidence such as DNA and protein sequences.
Step-by-step explanation:
To document the most recent common ancestor (MRCA), scientists deploy various techniques that combine morphological and molecular evidence. One technique is examining the fossil record to identify morphological traits of extinct organisms and infer relationships. Additionally, the construction of a cladogram can visualize connections between current species and their ancestors. However, the fossil record alone can be incomplete or ambiguous.
Another key approach is using the concept of a molecular clock, which compares DNA or protein sequences to estimate when species diverged from a common ancestor. Mutation rates are calculated based on conserved protein sequences. For organisms like prokaryotes, which evolve relatively fast, refining molecular clocks is crucial for accurate timing. Computer technologies, including polymerase chain reaction (PCR) and statistical algorithms, assist in analyzing genetic material to correct for random similarities in DNA that could mislead phylogenetic relationships.