When you classifying people it is more than basing people on skin tones it is classifying people based on physical appearance, geographic origin, and genetic similarity.
Physical appearance
Skin Color
People in Spain, Algeria and China have similar skin tone, but are still thought of as different "races." Even people in southern India are as dark as many Africans. Skin color is distributed geographically and it tends to correlate with sunlight and latitude not "race."Skin color is given based on geographics, the closer to the equator you are the darker your complexion the further you are the lighter your complexion, due to the melanin in your skin.
Nose Shape
The width and shape and shape of the nose is often considered a "racial" characteristic. It is typically said that Black people have wider larger shaped noses and people of other skin tones typically have smaller or petite shaped noses. People in east Asia and southeast Asia have different nose shapes but Germans and Arabians tend to be similar in nose shape more than Arabian and Norwegians.
Head Size
Head size is distributed geographically and does not vary between races. People near India, Sweden and South Africa on average have medium-sized heads and people in northern England and western African have larger heads.
We can map any number of traits and none would match our idea of race, that is because not one single gene or trait distinguishes all members of one so-called race from all members of another.
Geographic Origin
We think of global migration as a new idea but in reality humans have mixed, mated, and migrated throughout history. They have done so through the Early Human migration(70,000-10,000 years ago), Trade and Spread of Disease(500C.E.-1500C.E.), The Mongol Expansion(1200 C.E.-1500C.E.), The World Slave Trade(1500C.E.-1830C.E.), and the Recent Global Migration(1800C.E.-2000C.E.)
We are all 'Mongrels'. No human group has been isolated long enough to evolve into a genetically distinct race. We are all amalgamations of many past groups.
Genetic Similarity
Most of us can trace our ancestry back at least a few generations, but if you go far enough back in time, you find that you have millions of ancestors- every one of whom contributed to your DNA. Our DNA is made up of bits and pieces of DNA from millions or ancestors, dating back thousands of generations- all the way back to Africa. Humans are 99.9% identical genetically, genetic differences do not exist between individuals and between groups, but those differences do not follow racial lines.
References
Pbs.org and California Newsreel. Human Diversity. Race the Power of an Illusion. Retrieved from http://www.pbs.org/race/000_General/000_00-Home.htm
Dictionary.com. Define Race. Retrieved from http://dictionary.reference.com/browse/race?s=t
The National Coalition for Health Professional Education in Genetics (NCHPEG) Committee. [2013]. Race and Genetics FAQ. Retrieved from
