Final answer:
The concept that living and extinct species evolved from the same ancestors is true, supported by the theory of evolution through natural selection, mutation, and speciation.
Step-by-step explanation:
According to the concept of natural variation, the statement that living and extinct species evolved from the same ancestors is true. Evolutionary theory posits that all living organisms, including humans, plants, and animals, share common ancestry but have undergone diverse evolutionary paths due to mutation, natural selection, and speciation. Charles Darwin's work provided substantial support to this view, illustrating how species diverge from common ancestors through time. Notably, the fossil Archaeopteryx exemplifies this idea, showing characteristics of both reptiles and birds, suggesting a common ancestry. Speciation, as part of evolutionary processes, can lead to the emergence of one or more new species from a single ancestral species, further supporting the concept of common descent.