This is the blog for GW students taking Human Evolutionary Genetics. This site is for posting interesting tidbits on: the patterns and processes of human genetic variation;human origins and migration; molecular adaptations to environment, lifestyle and disease; ancient and forensic DNA analyses; and genealogical reconstructions.

GWHEG figure

GWHEG figure

Friday, February 14, 2020

Molecular clocks - how they have improved and developed

The idea of a molecular clock is that you can date the divergence of species based on simple math of how quickly molecules diverge. This is not a new idea, but since it first came about, scientists have developed the technique and tried to improve the accuracy of its predictions. 

Although the general technique has held up as especially useful, it was clear that it was not very successful when it was applied to distantly related species. This led to the development of the Bayesian clock which could incorporate more information for more accurate predictions, as well as information on ranges and accuracy. These new methods allowed calibration from fossil assemblages to create a framework of data for the clock to work on. The more data that can be put into the calibration the more precise the data output. 

Another development was of relaxed clock models. This allows better predictive power as it does not assume that the rate of change of molecules is exactly the same in all lineages. This type of clock calculation can give better boundaries of maximum and minimum depending on the precision of the estimates. 

The development of molecular clocks, is a keen example of how original ideas can be extremely useful in science, but also needs to be updated and adapted with improving technology. Although the original principle of the molecular clock holds true, we can gain more and more information as genetic sequencing improves and genome wide sequences can be incorporated into the analysis. The clock methodology is still held back by the limitation of the fossil record to calibrate the model, and the biases in which areas of the tree of life we have genome sequences species.








Link to article: https://www.nature.com/nrg/journal/v17/n2/full/nrg.2015.8.html

Jack Richardson - Potluck 18th Feb.

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