How do biologists interpret these similarities

Q1. Barbara McClintock, famous for discovering that genes might move within genomes, had her meticulous work ignored for nearly 4 decades, but eventually won the Nobel Prize. Why was her work so distrusted?

Q2. Structures as different as human arms, bat wings, and dolphin flippers contain many of same bones, these bones having developed from very similar embryonic tissues. How do biologists interpret these similarities?

Q3. Oxygenic photo autotrophy can have been invented as long ago as 3.5 billion years ago (depending upon what evidence you trust). The atmosphere became oxidizing less than 2.4 billion years ago. Why the 900 million year discrepancy?