I never understood that ancient people had to press their fingerprints when concluding contracts. With this fingerprint, it can be used as important material evidence. Did you already have fingerprints? First of all, there was no DNA technology in ancient times, but from the appearance of fingerprints, the fingerprints of two people are essentially different. You can do an experiment with your family. In fact, the naked eye can see the difference between fingerprints. There was no concept of probability at that time. Until modern times, according to DNA statistics, the same probability of fingerprints was about one in 100,000. In ancient times, there were not hundreds of towns, and basically everyone's fingerprints were different, so the answer they gave was that everyone's fingerprints in the world were different. That's why I signed it. In addition, you may have seen imitations of other people's signatures in TV dramas, but you can practice with your family. You have to practice at least tens of thousands of times to learn to sign, let alone write an identical letter with 100 characters, which is very difficult. Therefore, fingerprints are the most effective. Until modern times, fingerprints have been used all the time, and sometimes even fingerprints can be distinguished with the naked eye without using electronic tools to measure them.