Final answer:
Life on Earth dates back to between 3.5 and 3.95 billion years ago. Softer evidence suggests possible microbial life 4.1 billion years ago. Earth formed around 4.5 billion years ago and life likely began shortly after the heavy bombardment period.
Step-by-step explanation:
The earliest clues about life on Earth date back to between 3.5 and 3.95 billion years ago, during the Archaean Eon. Solid geological evidence indicates the presence of actual life during this period.
Furthermore, softer evidence of microbial life, such as graphite and other potential remains, suggests that life could have existed as early as 4.1 billion years ago, near the end of the Hadean Eon.
The Earth itself formed approximately 4.5 billion years ago, and it is believed that life started quite early in its history, following the period of heavy bombardment, potentially in environments like shallow marine pools or deep-sea hydrothermal vents.