Photo by Earls37a.

Over at Nothing in Biology Makes Sense!, guest poster Gustavo Bravo explains why evolutionary biologists spend a lot of time thinking about how frequently DNA mutations occur.

There are two ways in which we can translate the number of substitutions between a pair of lineages into absolute dates. First, we can calibrate the clock against absolute times resulting from independent evidence such as fossil or geological dates. And secondly, we can measure directly the rate of mutation by comparing DNA or protein sequence data in present day organisms. Because the fossil record for some groups is incomplete and the dating of geological events remains controversial, some of those clocks are likely to produce inaccurate estimates of time.

To learn how re-setting the “molecular clock” has changed our thinking about human evolution, go read the whole thing.◼