What are some of the concepts about human nature

What is the theoretical basis to understand how species are related to each other? How has the modern approach changed from the way they did it in the past? Why do we not just consider two things that look alike to be related?

What are some of the concepts about human nature and the relationship between humans and nature that had to change before an evolutionary concept could develop?

Many anti-evolutionists believe that since science doesn’t have answers to all questions; scientific conclusions are not necessarily correct.  This attitude reflects a failure to understand the nature of science. What is the general nature of scientific thinking? In what way is science “self-correcting”?