Answer:
Before: (Darwin did) Physical features and behavior
Now:
DNA Testing
Explanation:
Similarities are often easy to see when one looks at two organisms that evolved from a common ancestor, and until recently, looking at physical features and behavior was the only way to determine how closely related two organisms are. However, now scientists can also analyze DNA to discover how closely organisms are related. Every living creature has DNA, which has a lot of inherited information about how the body builds itself. Scientists can compare the DNA of two organisms; the more similar the DNA, the more closely related the organisms. This method can also help when looks are deceptive. One example of looks being deceptive is: The bat and the crow both have wings, and the squirrel does not. From this, one may think that bats and crows are more closely related than bats and squirrels, while the opposite is indeed the case.
