Everyone's fingerprints are different, and modern instruments can easily distinguish them. It is very easy for modern instruments to identify fingerprints. Just like friends at work or school, they must have had the experience of punching cards with fingerprints. In ancient times, without these sophisticated instruments, why did the ancients still need to press fingerprints on documents?
As early as the Qin Dynasty, the ancients used seals or fingerprints to verify the integrity of this document. Mainly because the wooden slips at that time were very expensive, and all the important documents recorded in them needed to be kept secret. If you find that the lines of the seal or fingerprint are not completely aligned, you can easily identify whether the file has been opened.
With the development of the times, paper was invented. But there are still many people who can't read or write. So they represent their signatures by pressing their handprints. Once the handprint is pressed, this is the default and undeniable mark. This ancient man is more contractual than we modern people.
After the Song Dynasty, officials began to use fingerprints to determine cases. Because at that time the ancients found that everyone's fingerprints were different. But after all, there is no modern and accurate scientific method to distinguish them, so they usually distinguish the threads on people's fingerprints. You can also look at your fingers. The line on each finger is different. This can be seen clearly with the naked eye.
So after that, people will not only sign the written contract, but also press their fingerprints to prove that I wrote it or I agreed. To tell the truth, in fact, in ancient times, it was a good way to identify people, because in relatively closed ancient times. The correct rate of solving this case is still quite high.
It must be said that the ancient people's contractual spirit and intelligence are quite high.