Welcome to Slow English FM and Daily Random Facts. This programme shares clear, simple facts to help us understand the world and improve our English. This episode looks at how far back the history of sharks goes. The Natural History Museum says the fossil record of sharks and their ancestors reaches back about 450 million years. A fossil record is evidence of past life preserved in fossils. That date does not mean that modern shark species have existed for that entire time. The claim is about sharks and their ancestors across evolutionary history. There is another way to picture this long timescale: that history began before trees existed. So the story of sharks reaches back to a time before trees. The key point is not that every shark stayed the same. It is that the fossil record of this group stretches back about 450 million years, earlier than the history of trees. Stay with Slow English FM.