Humans have something in common - DNA (Deoxyribonucleic Acid) which is secretively hidden in our chromosomes. Since DNA is a type of nucleic acids which is made of from millions of nucleotides. Nucleotide is a basic unit of building a long strand of DNA - just like building a house; the basic units are the bricks, concretes and etc.
What is so mysterious about DNA?
Since it's a small structure with approximately 2.2 - 2.6 nanometers wide, it contains a genetic code that can be deciphered to unveiled the secrets of our body. Advances in DNA technology enable us to unlock the secrets of our body as to search for the meaning of mankind.
You look like your mom...you'd got the eyes just like your father...you're as strong as your uncle...
These traits can be explained as it is related to genes - genetic information that inherited from our parents - possibly contains sub-information about our ancestors. DNA can be treated as our entity - a living proof that makes us adapting to all sorts of surroundings.
This represents how humans are enabling to survive since human population had reached more than 6.6 billion as recorded on July 2007.
How do we look different among each other?
All of us differ to the type DNA - means that each of us has DNA which has different genetic information except individual twins who has identical DNA. People often being mislead by assuming fingerprint is similar to DNA.
Actually, humans have their own distinctive fingerprints and DNA but individual twins have different fingerprints. However, differences of DNA among races based on their appearances (phenotypic traits) have yet able to be distinguished as we need more time and effort to map and identify common distinctive traits at the DNA level.