There are several theories as to where Black people come from. Some are legitimate while others are so far off base they are accepted only by those with a racist or racialist ulterior motive. I'll address those after looking at the biblically based theories. In reality, the Bible doesn't really tell us where the various races come from, but it does provide some clues, and it is these clues, coupled with logic, that form the basis for the various theories.
The first theory is that when God confused the languages of the people at the Tower of Babel, he also created racial diversity. The second theory is that Adam and Eve carried the genetic traits for all the various races, and passed them on to their descendents. Personally, I think both contain some elements of truth. I'll explain, but first a brief lesson on racial genetics.
Most people believe the different races carry genes that are specific to their race. In other other words, there are Black genes, White genes, Hispanic genes, Asian genes, etc., depending on how many races one recognizes. This belief would, however, be untrue. In 2002, scientists at Stanford University discovered the differences between people was not a result of genes, but rather alleles. Alleles are variant mutations of a specific gene. For instance, every human, regardless of race has the exact same gene for hair. It is the alleles that cause the differences in hair color and texture. The reason this is important is, there are no alleles that are specific to race. In other words, there are no “Black” alleles, no “White,” or “Hispanic,” or “Asian,” or etc., alleles. The various alleles that cause different hair color, different hair texture, different skin pigmentation, etc., are found throughout all people around the world. There are no race specific alleles. There are no specific, distinctively separate genetic identities that can be legitimately referred to as “races.” What this means, particularly to the question at hand is, there is no such thing as race. Every human being that has ever been born, or will be born, belongs to the same race. Genetically speaking, every human being, regardless of skin color or physical features, is identical. We all have the exact same genes. Race (as in Black, White, Asian, etc.) is nothing more than a social construct, and not a biological one.
Interestingly, some people will point to diseases such as sickle cell anemia and cystic fibrosis are an indicator of race, pointing to the perception that sickle cell is found only in those of African descent and cystic fibrosis as being found in those of Northern European descent. This perception, however, is inaccurate. While it is true that those of African descent are more likely to contract sickle cell anemia, it is also common among Hispanics, South Asians, people from the Middle East, and, surprisingly, Caucasians from Southern Europe. It is not strictly a “Black” disease. As human beings, we share 99.9% of our DNA with each other. The 0.1% difference is the result of environmental factors, which produce various skin pigmentation and so forth; and may be more properly defined as ancestral history rather than race. This brings us back to the biblical theories mentioned earlier.
As the progenitors of the entire human race, it is obvious that whatever genetic traits, including allele mutations, which are found in modern humans would also have been found in Adam and Eve. This doesn't mean they would have exhibited each of these traits, but they would have carried them in their DNA and they would have passed them on to their descendants.
When the Lord confused the languages of the people of the earth (Genesis 11:1-9), logically the people separated into groups that spoke the same language as they moved away into different areas of the earth (verses 8-9). Thus, people who spoke one language went to one area, while those who spoke a different language went to a different area, and so on. This separate would significantly decrease the gene pool in each specific group as the people no longer had the entire human race to intermarry with. This served to create a type of inbreeding that increased exponentially thus causing the gene pool to decrease at the same or similar rate. The result would be that those of the same language group would begin to exhibit the same or similar physical characteristics.
The alleles mentioned above that would have existed in Adam and Eve would be affected by the geographical location of the various language groups. Science has shown that recessive alleles (those inherited from our common ancestors – Adam and Eve) are influenced by our geographic location, thus resulting in biological characteristics suited to specific geographic locations. For example, darker skin that is better suited to excessive heat, a layer of insulating fat that helps in colder climates, body size (and surface area) suited to excesses in climate, and so forth. This is commonly known among scientists as human biological adaptability. In reality, however, we know that it is nothing more than than part of creation. God created our bodies in such a way as to make it possible for us to biologically adapt to our environment.
So to answer the initial question of, where do black people come from, they come from Africa, where their ancestors had migrated after the confusion of the original language and the dispersion of the people at the Tower of Babel.
Where Black People Did Not Come From
Just as important as the question of where did Black people come from, is the issue of where they did not come from. Over the course of the past century or so, there have been numerous faulty theories about where Black people come from. Each of these faulty theories have one common denominator that links them all together, and that is racial hatred. These faulty theories can be grouped together in three categories, as all of them are variations of these three main faulty theories. They are, the Myth of the Hamites; the Seed or Curse of Cain Myth, and the Myth of the Serpent Seed; the Myth of the Kenites; and the Heresy of Kinism.
The Myth of the Hamites
This is a popular myth among many White Supremacist groups, and was often used to justify the sin of slavery. The Myth of the Hamites states that when Noah cursed his son Ham, the curse was a black skin on Ham and a curse that made his descendants into servants or slaves of everyone else. They go on to say that Ham then left and migrated to Africa and became the progenitor of all Black Africans, passing the curse onto them. A review of the passage in question (Genesis 9:18-27) reveals a significant problem with this theory:
“18 The sons of Noah who went forth from the ark were Shem, Ham, and Japheth. (Ham was the father of Canaan.) 19 These three were the sons of Noah, and from these the people of the whole earth were dispersed. 20 Noah began to be a man of the soil, and he planted a vineyard. 21 He drank of the wine and became drunk and lay uncovered in his tent. 22 And Ham, the father of Canaan, saw the nakedness of his father and told his two brothers outside. 23 Then Shem and Japheth took a garment, laid it on both their shoulders, and walked backward and covered the nakedness of their father. Their faces were turned backward, and they did not see their father's nakedness. 24 When Noah awoke from his wine and knew what his youngest son had done to him, 25 he said, 'Cursed be Canaan; a servant of servants shall he be to his brothers.' 26 He also said, 'Blessed be the Lord, the God of Shem; and let Canaan be his servant. 27 May God enlarge Japheth, and let him dwell in the tents of Shem, and let Canaan be his servant.'”
The primary problem of this myth, as can be seen in the passage, is that nowhere is Ham said to have been cursed with a black skin. In fact, Ham isn't actually cursed at all, Noah cursed his son Canaan, not Ham! Proponents of the Myth of the Hamites often claim that the name “Ham” actually means “black” in Hebrew, thus validating the Hamite myth. In reality, however, it does not mean “black.” Reading the passage in a Hebrew Interlinear Bible that is keyed to Strong's Exhaustive Concordance, gives the Strong's number H2526 to the name “Ham.” Strong's defines the word as a personal noun, “Cham: a son of Noah, also his descendants. Part of Speech: proper name, masculine person. Transliteration: Cham. Phonetic Spelling: (khawm).” It is a personal name, a noun, and it is used 16 times in Scripture, and always as a reference to the son of Noah or his descendants. Strong's also notes that it is also a Hebrew word meaning “Hot” (see Strong's H2525), and it is an adjective, a descriptive word. It is used only two times in the Old Testament; in reference to hot bread (Joshua 9:12) and hot garments (Job 37:17). It does not mean “black” as those who subscribe to this myth claim.
The Myth of the Seed of Cain
Also known as the “Curse of Cain,” this myth is peculiar to the Church of Jesus Christ Latter Day Saints (the Mormons). This myth was popular during the early years of the Mormon church, and was not fully eradicated from the Mormon church until the late 1970's when the Mormon church officially lifted its ban on allowing Blacks into the Mormon priesthood. According to Mormon teaching, at some point prior to the creation of this universe, there was a war in heaven among the innumerable spirit children of the Mormon god. Some of these spirit children sided with the Mormon Jesus; while others sided with Satan, whom the Mormons teach was the brother of their Jesus. The Mormon god then punished those who sided with the Mormon Satan by placing them in the bodies of cursed people on the earth, specifically Cain and his descendants.
According to the Mormon church, Cain killed his brother Abel and entered into a covenant with Satan. Because of this, the Mormon god cursed Cain with a black skin and a flat nose. This “curse” was inherited by Cain's descendants, including one named “Egyptus.” The Mormon “Egyptus” married Noah's son Ham, who was also cursed, thus making all the descendants of Ham and Egyptus black and barred from the Mormon priesthood. Brigham Young, the second “Prophet, Seer, and Revelator” of the Mormon church promoted this racist doctrine publicly. In one instance, he stated, “the Lord put a mark upon him” referring to Blacks, “which is the flat nose and black skin....[and that] they should be the 'servant of servants.'” (LDS Journal of Discourses, Vol. 7, page 290). The Book of Mormon, in “2 Nephi 30:6”, also promoted racism. It stated that once the cursed Blacks became righteous (presumably converting to Mormonism), they would become “white and delightsome.” This racist statement stood unchanged in the Mormon scriptures until 1981 when it was finally changed to “pure and delightsome” (which still implies that Blacks are something less than pure).
The Myth of the Kenites
Also known as the “Serpent Seed” doctrine, the Myth of the Kenites is popular among White Supremacists, and the followers of “pastor” Arnold Murray of The Shepherd's Chapel, a television ministry. (note, Murray passed away in 2014. His son Dennis Murray has taken his place). According to Arnold Murray, the serpent had sexual relations with Eve, and the result of that union was her son Cain. White Supremacists have taken the Serpent Seed doctrine promoted by Arnold Murray, and elaborated on it, teaching that Cain was cursed by God, and that curse was dark skin. They insist the Bible supports this, and they point to Moses marrying Zipporah, a Midianite as proof. They teach the Midianites are also Kenites, and the descendants of Cain. They then conflate and combine Moses' two wives – Zipporah the Midianite and his second wife who was a Cushite woman, into a single person, and state the Midianites were also Cushites, and therefore, Moses married a Black Midianite, who was a Kenite, therefore Kenites are Black, therefore Cain was cursed and marked with a black skin, therefore, Blacks are cursed people.
The problem with this myth is, that it is not supported by Scripture, but it actually refuted by Scripture. Genesis 4:1 states, “Now Adam knew Eve his wife, and she conceived and bore Cain, saying, 'I have gotten a man with the help of the Lord.'” Clearly, Cain is the actual offspring of Adam and Eve, not Eve and the serpent. Furthermore, Exodus 2:15-22, which relates the marriage of Moses to Zipporah the Midianite, clearly takes place before the exodus; while Numbers 12:1, which relates that Moses had married a Cushite woman, takes place during the exodus, thus demonstrating that Moses was married twice, first to a Midianite woman, and second to a Cushite woman. The entire Myth of the Serpent Seed/Kenites falls completely apart when compared to Scripture. It is unbiblical and it is racist. Those subscribing to this myth are engaging in sin.
The Heresy of Kinism
Kinism is nothing more than a re-working of the Myth of the Hamites and the Myth of the Kenites. In short, Kinists believe and teach that both Cain and Ham were cursed by God with a black skin, and their descendants, who are also cursed, are the Africans, and all Blacks who have descended from Africans. In addition to this, Kinists are also rabidly anti-miscegenation. They condemn any mixing of the races, teaching interracial relationships are an abomination to God. To support this belief, they often point to the confusion of language and the separation of the people at the Tower of Babel (Genesis 11:1-9). Kinists teach that while the people of the earth wanted to join together as a unified people, God viewed this as an abomination, and so separated them in order to prevent any interracial marriages and/or mingling of the races. Of course, this is so far from the truth of Scripture to be laughable, and yet this is what Kinism teaches.
Scripture, on the other hand, does not condemn interracial marriage at all. In fact, there are several examples of both intercultural/inter-ethnic marriages, and interracial marriages. For example:
Samson and Delilah (a Philistine) – an intercultural/inter-ethnic marriage
Joseph married Asenath (an Egyptian) – an interracial marriage [in fact, they had two sons, Manasseh and Ephraim, who were thus of mixed race]
Moses married Zipporah (a Midianite) – an intercultural/inter-ethnic marriage
Moses later married an Ethiopean woman – an interracial marriage
Rahab (a Canaanite) married a Jew – an intercultural/inter-ethnic marriage
Ruth (a Moabite) married Boaz – an intercultural/inter-ethnic marriage
Esther married king Ahasuerus – an intercultural/inter-ethnic marriage
David married Bathsheba (a Hittite) – an intercultural/inter-ethnic marriage
Solomon married the Shulammite Woman – an interracial marriage
Conclusion
Intercultural/inter-ethnic and interracial marriages are not condemned by God as the Kinist believes.
God does not prohibit marriage (intercultural or otherwise) except when it involves a Christian marrying a person who is not a Christian (2 Corinthians 6:14). In fact, as far as God is concerned, when it comes to Christians, “There is neither Jew nor Greek, there is neither slave nor free, there is no male and female, for you are all one in Christ Jesus.” (Galatians 3:28) and, “Here there is not Greek and Jew, circumcised and uncircumcised, barbarian, Scythian, slave, free; but Christ is all, and in all.” (Colossians 3:11).
We've looked at where Black people (and all people) come from, and learned that all people come from the same common ancestors, namely Adam and Eve, and then later, Noah and his wife. We've also learned where Black people did not come from, namely as the result of a curse on Cain or Ham. Hopefully this has been beneficial as well as educational.
Sources:
Genetic Structure of Human Populations
https://web.stanford.edu/group/rosenberglab/papers/popstruct.pdf
There Is No Such Thing as Race
http://www.newsweek.com/there-no-such-thing-race-283123
Do Races Differ? Not Really, Genes Show
https://www.nytimes.com/2000/08/22/science/do-races-differ-not-really-genes-show.html
Taking Race Out of Human Genetics
http://www.sun.ac.za/english/faculty/healthsciences/cmel/Documents/taking%20race%20out%20of%20human%20genetics.pdf
The Apportionment of Human Diversity
http://www.philbio.org/wp-content/uploads/2010/11/Lewontin-The-Apportionment-of-Human-Diversity.pdf
Race Is a Social Construct, Scientists Argue
https://www.scientificamerican.com/article/race-is-a-social-construct-scientists-argue/
Frequently Asked Questions About Genetic and Genomic Science
https://www.genome.gov/19016904/faq-about-genetic-and-genomic-science/
Why People Keep Misunderstanding the 'Connection' Between Race and IQ
https://www.theatlantic.com/national/archive/2013/05/why-people-keep-misunderstanding-the-connection-between-race-and-iq/275876/
Race in a Genetic World
https://harvardmagazine.com/2008/05/race-in-a-genetic-world-html
Nature Genetics “Implications of biogeography of human populations for ‘race’ and medicine”
https://www.nature.com/articles/ng1438.pdf