Question

how did the earlier scientist and their contributions dirctly affect the discoveries of later scientist

Answer 1

Science builds upon itself. Earlier scientists discovered principles which are used to prove theories today. For example Charles Darwin proposed the theory of natural selection. Thanks to his work, we are now able to explain how species evolved over time - including ourselves.

Answer 2

The study of science is really a study of history. The basics of physics and chemistry were being figured out a couple hundred years ago. The science of geometry and algebra were understood by the "scientists" of ancient Egypt.