There are several methods for establishing evolutionary relationships, including comparing morphological, molecular, and behavioral traits, as well as studying the fossil record. Each of these methods has its strengths and limitations, and the most effective method depends on the research question and the organisms being studied.
However, molecular methods, specifically DNA sequencing and analysis, are generally considered to be the most effective at establishing evolutionary relationships. This is because DNA is the hereditary material that is passed down from generation to generation, and changes in DNA sequences over time reflect the accumulation of genetic mutations that drive evolution.
By comparing the DNA sequences of different organisms, scientists can determine the degree of similarity between them and use this information to construct phylogenetic trees that depict the evolutionary relationships among the organisms. This approach is known as molecular phylogenetics or molecular systematics.
Molecular methods have several advantages over other methods for establishing evolutionary relationships. For example, they can be used to compare organisms that are morphologically very different, or that have not been preserved as fossils. Additionally, molecular data can be analyzed quantitatively, which allows for more objective and rigorous comparisons than can be made with morphological or behavioral data.
Overall, while there is no one-size-fits-all approach to establishing evolutionary relationships, molecular methods are generally considered to be the most effective and powerful tools for this task.