Question

The minimum age of the LUCA (last unique common ancestor) is the age of the oldest fossils that can be identified with certainty as close relatives of present-day prokaryotes and eukaryotes. Such fossils are about ________.

1) 3.8 billion years old

2) 2 billion years old

3) 542 million years old

4) 3.28 billion years old

5) 65 million years old

Answer 1

The oldest fossils of cyanobacteria, which are related to present-day prokaryotes and eukaryotes, suggest that the minimum age of the Last Universal Common Ancestor (LUCA) is about 3.8 billion years.

Step-by-step explanation:

The minimum age of the Last Universal Common Ancestor (LUCA) is suggested by the age of the oldest fossils that closely relate to modern prokaryotes and eukaryotes. These fossils belong to domain Bacteria, likely cyanobacteria, and are about 3.5 to 3.8 billion years old. They showcase relatively complex structures and, for prokaryotes, larger cell sizes. These distinctive features make such fossils recognizable compared to the much smaller and less complex cells of other prokaryotes. The stromatolites, dating around 3.7 billion years, further support the existence of prokaryotic life forms living in communities at the time. As for eukaryotes, their earliest fossil evidence dates back to about 2 billion years ago. Therefore, considering the provided options, the correct answer would be 3.8 billion years old, which aligns with the age of the oldest identified fossils related to both domains.