Final answer:
Before Darwin, those who studied living organisms assumed they could organize and classify organisms based on complexity.
Step-by-step explanation:
Before Darwin, those who studied living organisms assumed they could organize and classify organisms.
Early thinkers believed that organisms belonged to a ladder of increasing complexity, and scientists attempted to organize all living things into classification schemes that demonstrated an increasing complexity of life. However, over time, scientists came to understand that life was constantly evolving, and Charles Darwin's theory of evolution provided a rationale for grouping and naming living things based on their evolutionary ancestry.
Today, scientists compare the anatomy, embryos, and DNA of modern organisms to understand how they evolved, and they classify organisms based on their evolutionary relationships.