What did darwin's studies of vestigial organs and atavisms tell him about the process of evolution? : a. the appearance of such structures indicates that mutations have a strong impact on our evolution.
b. mutants are real and not just a product of science fiction writing.
c. atavisms and vestigial organs did not strongly contribute to his understanding of evolution via natural selection.
d. humans share a deep evolutionary ancestry with other animals that can be seen in reappearing atavisms or body parts that no longer seem to have a function.

The correct answer is option d. "Humans share a deep evolutionary ancestry with other animals that can be seen in reappearing atavisms or body parts that no longer seem to have a function".

Explanation:

A vestigial organ or vestigial structure is an anatomical feature that no longer seems to have a function, but they used to serve a purpose in an ancient form of an organism in the past. Atavisms, are vestigial organs that seem to reappear after having been lost through evolutionary change. Charles Darwin's studies on the subject made him conclude that humans share a deep evolutionary ancestry with other animals that can be seen in reappearing atavisms or body parts that no longer seem to have a function. He published his studies on human vestigial organs and atavisms in his book "The Descent of Man, and Selection in Relation to Sex".