Humans and their close relatives (hominins) have been around for roughly 5 million years. What percentage of geologic time is represented by the history of this group?

Approximately 0.11% of the geological time.

Explanation:

Evidence from radiometric dating indicates that Earth is about 4.54 billion years old.

If humans and their close relatives (hominins) have been around for roughly 5 million years, the the fraction of this time to the geological time is calculated below

4.54 billion years = 4.54 x 10^9 years

5 million years = 5 x 10^6 years

percentage = ≅ 0.11% of the geological time.