Molecular phylogenetics is the study of organisms on a molecular level to gather information about the phylogenetic relationships between different organisms. This discipline is used to map out the evolutionary history of an organism or group of organisms. For those who have wondered about why scientists can be so precise when they give estimates of when various events in evolutionary history occurred, the answer lies in molecular phylogenetics.
This branch of the sciences relies on the fact that genetic change is a constant. With each generation, organisms change slightly, and the rate of change tends to be constant and reliable. Using this information, people can compare genetic information between different species and determine when they diverged from each other by examining their degree of similarity and dissimilarity. Researchers can also use this information to construct an evolutionary timeline.
For example, if the DNA of a cat and the DNA of a bird are examined, there will be significant differences, indicating that the two species diverged a long time ago. By contrast, a cat and a rat might have more similarities, showing a more recent common ancestor. Molecular phylogenetics can be used to construct a phylogenetic tree, in which a common ancestor is shown as the root, and branches describe the diverges which occurred over time.
Examining genetic material of living species can reveal interesting information about common ancestors and when species diverged from their common ancestors. For example, humans appear to be related to the great apes, but they are related more closely to some apes than others, illustrating that human and ape species diverged from their common ancestor at different points. Using information about the dissimilarities between related species and the known rate of genetic changes, researchers can posit when the various divergences from a common ancestor occurred.
Molecular phylogenetics cannot explain why evolution occurs, but it can be used to trace the path of evolution to learn more about the history of life on Earth. Researchers interested in topics like why various organisms became extinct, what kinds of pressures drove evolution in others, and how life on Earth emerged in the first place can use molecular phylogenetics as part of their information-gathering toolboxes.
Several researchers have been credited with a quote which roughly runs along the lines of “nothing about life on Earth makes sense without evolution,” referencing the complexity of life on Earth, the obvious history found in the fossil record, and the history found in the DNA of organisms from hedgehog mushrooms to blue whales. Molecular phylogenetics is used to untangle the complex web of evolution so that evolution makes sense to researchers.