George Curvier was a naturalist who proved that all the fossils found are not related to the present day species of the different organisms. He studied the woolly mammoths and then, compared these fossils to the modern-day elephants and then found that they are not similar. He based on these observations concluded that many species existed on Earth which are not present anymore as they got extinct. Based on this comparison method of the Curvier it can be said that the scientific ideas are made by comparing the past and present organisms.
Hence, the answer is 'scientific ideas are made by comparing the past and present organisms'.
