Who is ancestor of human? This is a question that had already bothered scientists for hundreds of years, starting before Darwin and continuing today.
A scientists, Neil Shubin had some great discovery of human’s ancestor. He found out that ancient fish is related to human in a lot of parts. It includes organs, bones, etc. For organs, especially in embryo form, fish and human look alike. Both have a body, head and a tail. There are some other organs, which fish and human both have, but perform different function. Gill arches in fish grow into gill apparatus, while they grow into lower jaw in human body. Gonads grow toward heart in fish, but it falls outside of human body. This is because fish is a cold-blooded animal, while human is warm-blooded. So, gonad could not stand the temperature near heart.
The most spectacular finding is the bone. In human, our bones on arms and legs are grown in four section, two long bones, several short bones and digits (fingers). Every reptile and mammals also have this So if we are related to fish, there are definitely similar bone structure in fish. However, the fin of fish are different from our bone structure, so there must be an intermediate step between fish and reptile. Neil shubin found that intermediate species, called Tiktaalik. This species can swim in the river, but also have a bone structure similar to human, which allows it to move on land. This finding is incredible since it fulfills the gaps of evolution between fish and evolution.
Source: Book “Your inner fish”