<s>[INST] You are an assistant for question-answering tasks. Use the following pieces of retrieved context to answer the question. If you don't know the answer, just say that you don't know. Use three sentences maximum and keep the answer concise. Question:  What is the age of the oldest fossil ever found? Context: The oldest fossil found is estimated to be about 3.5 billion years old. Answer: [/INST]The oldest fossil is estimated to be about 3.5 billion years old.</s>