Why are people from sub saharan africa considered a single "race"?

Well, "race" is a socially-constructed grouping based on skin color, and who is part of what racial group varies depending on what people are doing the grouping. Biologically and scientifically, sub-Saharan peoples are not considered a single race, because race is not a fixed category. Forensics people may be able to identify certain traits as probably African, and you can further describe people from different parts of Africa as generally having some physical features that would let you break them down into a West African group, East African group, etc., but genetically and anatomically these groups do not actually exist as a consistent way of measuring or classifying. So the racial groups are just a matter of who is doing the grouping. This grouping has generally been done by white Europeans and Americans, almost exclusively based on skin color. White people a few centuries ago (and more recently) weren't too interested in whether someone was Nigerian versus Kenyan-- they just saw everyone south of the Sahara as "black." The white Western world divided things up into mostly just white, black, asian, and native american. However, if you ask people in places like South Africa or Brazil, they have whole other systems for identifying races based on skin color, and think of racial groups in a very different way. What Americans call "black", a Brazilian would divide up into maybe 5 different shades based on skin tone. All these racial groupings are also all tied into discrimination and colonialism as well. The point is, people in sub-Saharan Africa have been considered a single "race" by some people historically, but but these categories are subjective. Sub-Saharan Africans are NOT considered a single race from a scientific perspective, because the whole idea of race falls apart when you attempt to scientifically define it.

The answer is that there are no 'races' of modern man. There is not enough genetic diversity to speak of races. What are referred to popularly (and in pseudo-science) are arbitrary definitions based on phenotype, not genotype. Much of 'race science' dates from the 19th century, and has no basis in genetics, as subject understood then even more thinly than it is today. However, now we have the human genome, the understanding of which is being added to every year and will probably for decades to come. Even this year, haplogroup R1b was subdivided into R1b1a, through the discovery of the genetic marker R-V88. And that is going to continue too, as more people are getting tested. What all the genes do and how they interact is of course still mainly a mystery. In biology, race or sub-species (20-25% of genetic diversity within a species) is considered that last stage before speciation (a species being the largest group of organisms that can produce fertile offspring - wolfs and dogs can, horses and donkeys can't as mules are infertile). Dr. Richard Lewontin, looking at the diversity of blood types back in the 1970s, found that within phenotypic races, there was only 6-8% of genetic diversity, both negating the existence of races among modern humans, and disproving the multi-regional theory of human evolution (the mainstay of most racist thought), instead supplying evidence for an origin that is both common and very recent. This data was independently backed up by the Human Genome Project, looking at individual strands of DNA. Check out dr. Richard Lewontin's interview at PBS, "Race, The Power Of An Illusion".

Because history books are written by Europeans. You are absolutely correct, people from different parts of Africa have very different physical characteristics. There are huge genetic differences, too. As a white American woman, my genes are as similar to a Nigerian man's genes as that Nigerian man's genes are to a those of a person from South Africa. Its not just Africans who get lumped together. I dont know how many times I have had to explain that people with brown skin from the middle of Eurasia are not all Arabic, or that "Chinese" is not an appropiate label for people in Laos. I wonder if people who live in Africa refer to white people as Europeans...

Race is defined as those major divisions and subdivisions of mankind. Race is denoted by language, descent, physical characteristics and culture but more often than not, language is the deciding factor of race. "An examination of world language taxonomy is, to a very large degree, an examination of world racial and subracial taxonomy." [1] In more modern materialist scientific discourse, race is defined by a phenotype inherited from one generation to the next. From the Tower of Babel to the later 20th century this was an accepted fact of reality. Throughout man's history, men have been divided and have divided themselves by race. The races of men are an easily observable fact of nature and a product of common sense. They are part and parcel of what makes up the Natural order. Race is how man has cataloged the diversity of mankind in his world. Race is separation but also of boundaries. Race is a unit. It is product of the natural human cognition to "Define and Divide". This does not mean that race is a social construct but that man in order to know his surroundings, puts names on differences whether it be mineral, chemical, plant, animal or himself. Differences existed before man has named them so race is not a social construct but nomenclature applied after the fact. Differences exist and so man names, catalogues, those differences. Putting the title of race on diversity of mankind is after they have existed. Thru the principle of macrocosm/microcosm, race is no more than a family writ large; it is a familial grouping of related families.[2] Each of these groups have a sense of belonging to their own kind. Racial groups often report on their descent from a single father called a Patriarch. In Classical Antiquity, many races could name their patriarch; i.e. the Hebrews could name Abraham as their patriarch. Lineage or geneology is an important makeup of the identity of ethnic groups. Classical civilizations from Rome to China tended to invest much more importance in family or tribal affiliations than in physical appearance. [3] The concept of the races of men are synonymous with the word "breed" used to differentiate different kinds of cattle and dogs. All cattle are one, yet there are different breeds such as Holsteins and Hereford. All dogs are one, yet there are different breeds of dogs from Great Danes, Bloodhounds, to Chihauhaus. Whereas the word "breed" is used with animal species, the word "race" is applied to mankind. The sub category of race is called "tribes". For instance, the Hebrews are a race that had twelve tribes. The Doric race was divided into three tribes; i.e. the Hylleans, the Dymanes, and the Pamphylians. Another word for a subdivision is "clan" used in Scotland. The races of men are not only distinguished by language but also by physical characteristics, traits and mentalities; this concept is called racism or ethnicity In view of the diversity of mankind, history records differences of outcome amongst the races of men; some have achieved a better standard of living or have accomplished something no other race has. This has lead to some races through their cultural accomplishments and/or military achievments to think that their race is superior or more gifted than others; this is called racialism.