I've done this topic twice. The first time I wrote the class a letter from a scientist in London asking them to search their school garden for clues to their next topic which he needed help researching and sending all the information they found out back to him. The second time was similar but I asked one of the office staff to come to the classroom to collect a package and letter which had arrived. Both times the children found lots of bones and teeth/received a box full of bones. They loved it and we're very excited to find out lots about their new topic.