The exact purpose of fingerprints is still unknown, but there are a few theories about why we have them.

• Improved grip. The ridges on our fingertips help us grip objects more effectively. This is especially important for tasks that require a lot of dexterity, such as climbing, picking up small objects, or throwing.
• Increased tactile sensitivity. The ridges on our fingertips also increase our tactile sensitivity, which is our ability to feel things. This is because the ridges trap sweat and oils from our skin, which create a sticky surface that helps us feel even the smallest of textures.
• Protection. The ridges on our fingertips can also help protect our fingers from injury. They act like a kind of armor, helping to cushion the fingers from impact.
• Unique identification. No two fingerprints are exactly alike, which makes them useful for identification purposes. This is why fingerprints are used in forensics and security applications.

It is likely that fingerprints serve a combination of these purposes.

As for why fingerprints are left behind when we touch things, it is because of the combination of the ridges and the sweat that our fingers produce. The ridges trap sweat and oils from our skin, and when we touch something, these substances are transferred to the surface. This leaves behind a visible impression of our fingerprints.

Fingerprints can be used to identify people because they are unique. Even identical twins, who have the same DNA, have different fingerprints. This is because fingerprints are influenced by a variety of factors, including the genes we inherit from our parents, the environment in the womb, and the way our fingers develop as we grow.

Fingerprints are a fascinating and unique feature of the human body. They have been used for identification purposes for centuries, and they continue to be an important tool in forensics and security.