Final answer:
Today's evidence for a common ancestor in evolution includes comparison of DNA sequences, the examination of fossil records, and the study of homologous and vestigial structures, which all support Darwin's theory.
Step-by-step explanation:
The question pertains to Charles Darwin's theory of evolution and the present-day evidence that supports the concept of a common ancestor through the study of comparative DNA sequences, fossil records, and anatomical and embryological similarities. For example, similar DNA sequences among different species are considered one of the strongest evidences for evolution, indicating that species with more similarities in their DNA are more closely related evolutionarily.
Additionally, homologous structures in different organisms, such as the similar bone structures in the limbs of humans, dogs, birds, and whales, point to a common ancestor. These structures have different forms and functions but retain the same basic layout. Vestigial structures, such as pelvic bones in whales or wing remnants in flightless birds, also support the idea of common ancestry as they are residual parts from ancestors that had a use for them.
Today's understanding of evolution has been greatly enhanced by the ability to compare genetics directly, which was not possible in Darwin's time. The fact that humans and chimpanzees share approximately 98% of their DNA provides compelling evidence of a shared ancestry not too far back in evolutionary history.