Final answer:
The molecular clock is an evolutionary biology tool for estimating the time of species divergence from a common ancestor by measuring DNA sequence changes. The concept is complex due to variable mutation rates but aids in reconstructing the geologic history of species.
Step-by-step explanation:
The topic being questioned is a concept in evolutionary biology known as the molecular clock. This concept is a method used to determine the time of divergence of different species from a common ancestor based on DNA sequence or amino acid sequence differences.
By assuming a steady rate of genetic mutation, calculated as 2% sequence divergence per million years, scientists can estimate the ages of evolutionary events. This rate greatly depends on the species and the DNA regions studied. Molecular clocks can be compared with the fossil record to calibrate and refine evolutionary timelines, aiding in the construction of phylogenetic trees and understanding the geologic history of life on Earth.
However, the reliability of the molecular clock can be controversial due to the variable nature of mutation rates across different taxa and through different periods. Such concerns are taken into account when developing more accurate models of molecular evolution. This improved understanding of genetic change helps researchers unravel historical patterns of species' evolution, adaptation, and extinction events.