Unless you are an identical twin it's unlikely you've found anyone else who looks just like you. But, why do we all look so different? Felicity Bedford spoke to population geneticist Sir Walter Bodmer from Oxford University who is characterising thousands of faces as part of the People of the British Isles Project...
"Why" is because humans take a long time to reach survivable maturity, so we have evolved to recognise our parents and tribe at an early age. We are therefore extremely good at facial recognition, to the extent that Heathrow Airport is going to replace its e-passport machines with more humans because we are far quicker at detecting a match (or a mismatch) despite variants due to makeup, spectacles, facial hair, etc., than any machine.
The two sides of the brain process data differently. We use both sides of the brain at the same time. However, we are only conscious of one side of the brain at a time. The other side will be unconscious but complementary. The left brain is more differential and allows us to see differences. The right brain is more integral and allows us to see what things have in common.
"However, we are only conscious of one side of the brain at a time." Show me that study! Whales all look the same to me but whales know one another. Your basis has no facts so your conclusion is spurious. mrsmith2211, Sat, 23rd Jan 2016
Please define consciousness. alancalverd, Mon, 25th Jan 2016
To answer the original question, many factors must be considered.
An extrapolated question to why humans have such a variety of appearances, is why are the insides of humans, more uniform than the outsides? Why is the heart more uniform looking than the face? One would be hard pressed to tell a pretty person from an ugly person, by looking at the stomach or heart. Maybe a doctor can see these differences, but it will take a more trained eye than it takes to differentiate a face. A child can do that.
One question that was asked is what is consciousness?