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Genetics Out of Africa
Dr. Orville Boyd Jenkins

Question:
When scientists say that we are all "out of Africa" what do they mean? Do they mean that all human beings came from people whom we could identify today as Black Africans?

Answer:
"O ut of Africa" is primarily a geographic reference.  But it does also mean that all modern humans have one biological (genetic) source.  This term "out of Africa" means that all branches of study indicate that all the humans of the world are of one family, and share a sequence of DNA that indicates all of us descend from the same original parents.  The trail leads back to Africa.

The Original Community
From DNA comparisons of samples all over the world, specific enough information has been analyzed to narrow down information on genetic origins to an original community of 10,000 or fewer individuals.  These details and procedures are detailed in works by the specialists in that area.  This sequence of migration from Africa to other parts of the world is indicated by genetics and corroborated by archaeology, linguistics and other disciplines of study.

The people called "Black Africans" today are one of the descendant groups.  (And note that there is a wide diversity among the "African" groups, similar to the great variety of human types we may refer to as "Europeans.")  We cannot be sure what the physical colour or exact features of original humans were, but there are some studies that have tried to make sense of the details.  Note that these views are based (following the scientific method) on what has been discovered and determined up to now.  The picture may change or be clarified as more is discovered about human prehistory.

The Oldest Groups
The current people of the world who have the oldest indicators are not Black Africans, but the "Bushmen," the San people.  Pygmies of Africa, who tend to be black and look more like their Bantu-speaking neighbours, but are small, are the closest kin to the San people.  Some San languages are still spoken by peoples in northern Tanzania.  Oral traditions confirm the San as the "oldest" representatives of the human race.

In recent centuries, in Western, especially American, society, skin colour has become a defining factor in our delineation of various groups of peoples.  On this basis, misleading or false concepts of humanity have been promulgated under the rubric of "race."  But colour of skin is one incidental among the great variety of features that make up the whole human genetic pool.

In recent years, genetic studies have identified the gene change that caused lighter skin to occur in northern climates.  Dr Francis Collins describes this:

"Recently a major molecular cause of this change in skin color has been discovered in Europeans.  Specifically, the gene SLC24A5 turns out to be critical for the production of melanin, the predominant dark pigment of the skin and hair. ... 100 percent of Europeans have a mutation in SLC24A5 that impairs the function of the protein.... Asians share the fully functional version of SLC24A5, but have acquired mutations in other genes that result in lighter skin, while retaining black hair [Francis Collins, The Language of Life (NY: Harper, 2010), p 150]."

Genetic Drift
Skin colour is a question of historical factors deep in human history, thousands of years ago.  Apparently as different groups (families or larger groups) moved on from their larger group, gradual changes took place.  These minute changes are explained in various technical sources, explaining how DNA reproduces and recombines generation to generation.

Genes are reorganized, placed in different order on the same chromosome, or at times shifting chromosomes.  This is called 'recombination."  Additionally a gene may be slightly damaged in the process of cell division or recombination.  All the processes involved in the creation of offspring result in slight differences over generations.  In the Y male chromosome, the sequence of such changes can be seen, since the tail of the Y chromosome is passed on to male heirs rather than recombined.  This is a primary source of information enabling recreation of human biological history.

Isolated human groups have a smaller number of people to mate with, so they develop their own characteristics as changes occur and mixes and matches occur in their tribe that were different from the larger group they used to be related to.  Scientists call this "genetic drift."  This appears to account for the general distinctions between broad human groupings around the globe.  Various additional distinction can be noted as you zoom in for more regional, then local analysis.  Thus it is a matter of perspective, how broad, how narrow, and what is your starting point for comparison (historically, genetically, politically, geographically).

The Changing Genescape
Thus African populations have also changed from their original, just as others have.  Some African peoples descend from ancestors who left Africa and some hundreds or thousands of years moved back.  These lines of migration have been mapped in detail in an attempt to reconstruct how it must have happened.  They try to show how the differences we have discovered must have happened and in what places.  They compare these genetic markers with tools and other cultural artifacts from archaeology in each region.  Oral traditions become helpful in some cases.

100% Ethnic?
Question:
If all human beings are out of Africa, why do we study DNA and then say that someone is 100% Chinese or 100% Caucasian;  Is there really such a thing as a "pure breed" human being?

Answer:
The people who would use the terms you cite are not the same people who have analyzed and outlined the genetic history of humanity.  Those aware of the genetic realities cannot speak in those stark absolute terms.  Such phrases arise, rather, from specific (often prejudicial) social contexts.  From a scientific or genetic point of view, the terms you cite have no meaning, as far as I know.

But these terms apparently would have in mind some starting point in history where one human group can be identified distinctly from another.  But a problem with the term "Chinese" is that it is both a geographic and political designation as well as an ethnic term.  And it is not addressing the same thing we have in mind in the discussion of human genetic origins.  It speaks in a different context, a recent point of social, racial or ethnic distinction in current or recent historical memory.

Vague Terms
The term "Caucasian" is even more problematic, since this is a vague reference, and technically refers to peoples living along the Caucasus Mountains or having origins there.  It is like most other local or regional terms for "race" or other physical or social distinctions, varying with the local context.  The term "Caucasian" is only a broad general reference term, not a clearly defined technical term.

On the other hand, each distinct visible physical type does have an identifiable origin along the continuum of human genetic history.  But that is what it is – a continuum.  At each level you can identify similarities and differences.  The patterns of migration and genetic drift have been reconstructed by scientists analyzing DNA and vigorously compared with information from other investigative disciplines.

I reference some of those on the various essays on ethnicity.  My intention here is not to recount or defend the state of genetic analysis.  These are broadly available on the Internet and books available from popular outlets.

Human Breeds?
There is no such thing as a "pure breed" human in the sense of one "type" or "tribe" or "race" of people being purer than any other.  There are thousands of ethnic groups in the world (About 10,500, as most analysts count them).  We all share the same ultimate history, and the current groups of humans we now know and sometimes refer to as "races" are mixed.  The history of every human population indicates they came from somewhere else at some point!

Oral traditions of all peoples include stories of migration and mixing.  The DNA story says the same.  Humans are nomads, sometimes willingly, sometimes under the duress of living conditions.

It is characteristic of languages and cultures to continue changing and developing to new forms and dividing into disparate forms.  But we also see situations in which languages die and ethnicities die.  Smaller peoples may move into a new ethnic stream and become part of another people.

One ethnic group might start speaking another language of a dominant people they relate to, and gradually lose their original language, but still consider themselves a separate people.  See my discussion on Assimilation patterns.

Because of all these factors, we have about 10,500 ethnic groups, but only about 6700 languages (though there are several thousand subdivisions of these languages, usually referred to as dialects).

Moving and Merging
Each time a group of humans move, recorded history indicates that there is intermarriage as well as conflict.  So a conquering people may become dominant by war, but will settle and over time in most cases, the original inhabitants and the newcomers will gradually become one.  It depends on how far you want to go back – everybody came from somewhere else!

The sub-groups we can identify are due to long periods of separate settlement and isolation in early periods of human pre-history and early history.  "Chinese" is a geographical and political term.  I don't know what it would mean to say someone is 100% Chinese.

The inhabitants of China speak thousands of languages (or hundreds depending on how you want to group their variations of speech).  Over the centuries of known history, all kinds of Asian peoples as well as Indo-European (or Caucasian) have moved in, settled, conquered, intermarried, etc.  It depends on how far back into their history and what part of their history you want to look at.

Dynamic DNA
The broad "Asian" facial features are due to the long earlier period of isolation, and the "genetic drift" that we referred to.  So when the world had few people, these differences were already slowly developing.  The possibilities for this were already in the shared DNA.

There are quite technical procedures through which DNA naturally changes over generations.  This is one of the reasons the distinct "racial" groups developed.  In all our historical period, we have seen peoples moving, intermarrying and changing.  But there is always some basic core in certain areas that might retain more of the ancient characteristics.

Question:
If all human beings came out of Africa, do all human beings have African genes? How close is the human family through this shared connection with Africa?

Answer:
There are two meanings involved here.  As indicated before, Africa is a place where we now know for certain that the original humans came from.  They developed there, and early changes occurred there that led to some varieties we can note, while they still lived in Africa.  Certain groups gradually moved out and finally across from East Africa to the Arabian Peninsula.

Genes Change, Peoples Change
No one was "African" as we now use the term. The perspective just means that they came from the land area that we now call Africa.  Some human groups stayed in that area and others moved off.  The movement from Africa to Asia, then Europe happened several times.  Asian groups moved farther east, and gradually most of the world was covered.

There was movement back and forth out of Africa and back into Africa.  Various waves of people moved in and out over the millennia.  I comment elsewhere on how active movement was from eastern Africa to Asia and back.

So the question is what you mean by the phrase "African genes."  People who now live in Europe do not have the same exact set of genes of the people who now live in Africa.  But neither of these are the original humans!  Peoples now living in Africa likewise do not have the same exact set of genes of the original human family.  Genes change – like populations change.  Every new individual's genes are unique in the history of the world!

Compatible Genes
What we mean is that all humans have the same broad set of genes, so we are all kin at the ultimate point.  Another way to think of it is that all humans are inter-fertile.  That is, in principle, one human individual from any specified identity group can mate with another individual from any other identity group and produce offspring.

It is possible to read "signs" in the way the DNA is organized, so that we can in fact find some of the same exact genes in a similar sequence.  There is a historical pattern, older genes and younger genes that show up in various populations in systematic ways.  The specialists deal with the details in their writings.

Differences in height, body shape, skin colour, head shape, etc., are variations that derive ultimately from the same broad original gene set.  But everyone's current gene set is different from any past gene set, since a characteristic of genes is that they change themselves and they recombine differently in each generation.  This is why gradual changes occur in one population that might not occur in another.  Scientists have now also learned that even diet can affect these differences.

This is also confirmed by the already obvious fact that we have seen in every part of the world in every period of recorded history – all humans can interbreed with all other humans!  There is only one species of humans.  (All other human/homo species have died out.  The last to overlap with our species (Homo sapiens) was the Neanderthals (Homo neandertalis) of Europe.)

The origin of this one human species is shown to be the land mass we now call Africa.  This common source is reflected in the fact that the shared DNA of any two individuals of the human race is 99.6%!  Dr Francis Collins discusses this in his book The Language of Life (NY: Harper, 2010).

"The DNA sequence of any two individuals is 99.6 percent identical, regardless of which parts of the world their ancestors come from. ... Only about 10 percent of those differences [between individuals] are useful in predicting which populations you belong to" [p 146].
Sometimes these observed differences are the basis of a nave categorization referred to as "race." Yet these superficial differences occur among humans whose DNA is 99.6% identical!

Question:
Do Africans have phenotypic diversity (dark skin/light brown skin, short hair/long hair, straight nose/broad nose) because of intermarriage with other "races" or did Africans have this diversity before intermingling?

Answer:
Well, DNA indicates that we all came from the same source, so much of the diversity was passed down to us from our earliest ancestors.  Spencer Wells, director of the Genographic Project, and author of several works on genetic history, comments on this.  "African populations are the most genetically diverse on the planet" [Deep Ancestry (Washington, DC:  National Geographic Society, 2006, p 152].

African Diversity
Wells makes his comments on a page showing quite different representatives of four ethnic groups who live in the African continent:  Bantu, Maasai, San and Pygmy (Twa).  He appears, thus, to mean that in Africa we find there is a wider range of population groups (ethnic groups, tribes, lineages, etc) that vary from each other.

However, Wells does also specifically speak of the differences between two individuals in the same village.  (Note he does not specifically say these would be related to the same family lineage.  Many villages would traditionally have been lineage settlements, but that is less and less the case now.  So this aspect is uncertain in my reading of Wells.  He may not be thinking of the lineage-tribe concept of ethnicity here.)
"Two Africans sampled from the same village could have Y-chromosome or mtDNA [mitochondrial (mother's line) DNA] lineages that are more divergent from each other than either is to a non-African"  [Deep Ancestry (Washington, DC:  National Geographic Society, 2006, p 150].

Dr Sarah Tishkoff of the University of Pennsylvania led a team that conducted DNA studies on a wide range of African populations.  Her team's findings confirm that no one African population group represents all the possible genes of huimankind.  They studied genetic material from 121 African populations.  Tishkoff concludes:

"In the past, [geneticists] studied just a few Africans, and suggested they were representative of the continent, but we've found that no population is representative of all of this diversity."

Gene Expansion
On the edges of Africa, it does appear that peoples from diverse communities outside Africa have contributed to the gene pool.  Gene patterns indicate movement back into eastern and northern Africa from populations who had previously migrated into Europe or Asia.  We, of course, don't know have physical evidence to confirm the specific visible characteristics of these prehistoric populations.

In some quarters it is common to use the term "race" primarily for skin colour distinctions.  Wells points out that in early migration history, DNA indicates that "the orignal inhabitants of North Africa were closely related to the Cro-Magnon settlers who first colonized Europe during the Upper Paleolithic" [Deep Ancestry, p.204].  But as far as I know, we don't know what colour their skin was.  Authorities caution that there are several unrelated genetic mechanisms that affect skin colour incidentally.

Some recent reactionary initiatives against the European racist attitudes toward Africa have gone to the opposite pole of the discussion, ironically asserting (either directly or indirectly) that "African" is equivalent to black.  In genetic discussions of related populations and genetic history or migration, we are talking about "tracer" genes, gene markers indicating sequence related to time, not specific physical features.  These Y-chromosome genetic markers don't tell us what color their skin was.  That is irrelevant.  Genetic analysts like Wells have donbe some speculation in their writings.  Check their writings.

However, in more recent historical times, we have definite knowledge of peoples of differing physical types who came to live on what we now call the African continent.  Before the Roman period, Semitic traders, sailors and settlers settled on the northern coast of Africa.  These Phoenicians came to be known by the name of the their primary city, Carthage, as Carthaginians.

In the later Roman period, a blond, blue-eyed Germanic tribe called the Vandals settled in that area, along with some of the Goths.  You can learn details about these cases from the speciaalists by doing a search on these topics or key words.

In the Horn of Africa, another Semitic people from southern Arabia moved across maybe two centuries or so before the time of Christ.  In more recent centuries, Arabs moved all over Africa east to west and north to south.  This added new diversity from the genetic drift that had developed to these genetic communities.  These Arabs (small groups, mostly traders and Sufi missionaries) contributed to the gene pool in what is now Ethiopia, Eritrea and Sudan.

In later centuries specifically Yemeni individuals in small groups moved among the populations from eastern to western Africa, some settling and becoming part of local peoples.  These are all in historical times. In the 19th and 20th century, small groups of Europeans also contributed to the gene pool as many married Africans in various parts of the continent.

Diverse Gene Pool
Other specialists likewise comment that the inhabitants of Africa are the most varied phenotypically.  I personally know that across Africa, African people vary considerably.  Certain groups, tribes or peoples known to be related are more alike than each is to unrelated peoples.

And like any other identifiable group of humans, and one African people may be distinctly different from another distinct African people.  Some peoples are more uniform and similar, while individuals in some population groups vary considerably individual to individual.  We find that in certain groups, individuals in some populations (tribes) are more varied while in other groups individuals are more similar.  Some African populations appear quite uniform in characteristics.

The Nilotic peoples, for instance are said to be the blackest in Africa, and in East Africa that is definitely so.  But some have commented that some West African peoples are starkly black also.  Some people called Bantu tend from brownish black to rich brown to chocolate brown to lighter reddish brown.  This may be because of the genetic drift mentioned earlier.  Or it might be due to intermarrying with other already lighter-skinned populations whose separate development led to a different colour of skin.

The Oldest Colour
For instance, the San ("Bushmen"), who retain the oldest DNA marker of the human race, tend to be reddish tan.  In Southern Africa, we know in recent times the Bantu people now known as Nguni in Southeastern Africa intermarried considerably with the San. The Nguni tribes (Zulu, Xhosa, and related tribes) show a wide range of variation in their populations.  Some have facial features very like the San, while others have very "African" features.

The Bantu languages of the Nguni peoles, similarly, have been heavily modified by the Khoisan language family, confirming an extremely long association between the two disparate genetic and cultural streams.  Colour of skin ranges to reddish as with the San, while some are quite dark.  In general skin colour is a rich golden brown.

In various articles I comment on some features like this and some of the historical combinations that might have been involved.  The Kikuyu people, among whom I lived over a period of 30 years in Kenya, have a wide range of physical types, height, and skin colour or facial features.  Their traditions and those of related peoples indicate that they also intermarried with shorter aboriginal peoples, perhaps a group related to the San.  There is a high population of Arab intermixture in East Africa.  The Swahili tribe is a varying mix of Arabs and Bantu Africans.  Their skin colour and facial features vary considerably.

Dr Collins Comments:

"There is good evidence that the original ancestors of Homo sapiens were dark-skinned. ... Dark skin was critical for ultraviolet radiation. ... Individuals who migrated out of Africa to more northern latitudes would have run into trouble maintaining adequate levels of vitamin D.  That process requires absorption of sunlight through the skin.  Thus dark-skinned individuals are prone to vitamin D deficiency in areas of limited sun exposure, causing a disease called Rickets. ... Thus individuals with lighter skin would have more reproductive success in northern climates and ultimately light skin became predominant [Francis Collins, The Language of Life (NY: Harper, 2010), p 149-150].

Note that it is only in certain periods with certain societies that skin colour has been the primary feature of separating or identifying populations.  Categories and terms and how they are divided, and who is considered higher class or lower class, etc., vary by region and political situation.

But as commented above, many characteristics – notably those that are found only in certain human groups, have been developed along the way through the various natural processes of DNA reproduction and change.  Genetic scientists tell us that genes change slightly and new characteristics, innovations, appear in certain population groups.  Various changes occur in different population groups.

Original and Derived Traits
Thus first, there were not originally any "races" in the sense that term seems to mean in your question.  But then, certainly, in our historical era, we can see that when two visibly different individuals mate and bear offspring, the children will exhibit certain characteristics from each parent.  This is true however similar or different the parents were from each other.  The details of genetics are quite complex, and I do not pretend to be an expert.  I do note in trying to follow the findings of the specialists, that much of the mystery of DNA continues to be revealed.

But note that African populations are just as dynamic as any other human group.  Just like anyone else, African populations move, they mingle, they diverge and diversify, they mix and merge.  African genes recombine like the genes of all human individuals.  No one has the "original genes."  This mechanism ensures the ongoing diversity, variety and novelty.

We see great variety now among human groups.  And we note that characteristics of the parents are handed down in various combinations among their children and descendants.  So among communities we can now identify, if an individual from that community marries someone from a visibly different community, then, yes, the children will inherit a variety of traits not prominent in one or the other of those communities.  If whole communities settle together and mingle over generations, the breadth of their differences will expand to be shared across the merged community as a whole.

Rainbow Hair and Eyes
In this way you get a population of people of European origin, who in one family might have children with varying hair and eye colour.  Red hair and green eyes, for instance, appear to be a genetic "innovation" that occurred in one particular human community, probably through a slight mutation.  Thus as these characteristics became primary characteristics in this clearly defined community of humans, they were distinguished from others with brown or black eyes.

When someone with red hair has children with someone with another colour hair, the various mix of the gene sets will yield different hair colourings for various children in the same family.  Thus now in North American communities you find people with all colours of hair eyes and skin in the same lineage group and nuclear families, because peoples who had origins in different population groups who had developed different characteristics from each other married and bore offspring who gradually exhibited a broad range of characteristics, which are now shared by the broad population.

This is just one common obvious example of mixing of unique characteristics from disparate population groups in our historical period.  Geneticists discuss these possibilities in their more technical focuses, so I am not trying to reproduce that here.

See related reviews and articles on this site:
The Amhara People of Ethiopia
Appreciating Differences
Colour, Race and Genetics in the Horn of Africa
Italians, Etruscans and Greeks:  Genetics and Ethnicity
Mapping Human Origins
My book reviews on this site
Our Genetic Journey
Race and Ethnicity in the Horn of Africa
The Sabeans and Other Ancient Genetics and Tongues:  Distinguishing Fact from Legend and Modern from Ancient
The Tigrinya (Tigray-Tigrinya) People
What is a People Group
What is an Ethnic Group

Related on the Internet:
Africa's Genetic Secrets Unlocked – BBC
Blood of the Isles British Genetics Website by Bryan Sykes
A Brief Genetic History of Man
European Genetic History – Wikipedia
     Includes excellent and extensive references to authorities
Genographic Project
National Geographic
Out of Africa's Eden by Stephen Oppenheimer
Prehistoric humanoid DNA - raises more questions than it answers
Saxons, Vikings, and Celts: The Genetic Roots of Britain and Ireland by Bryan Sykes (UK Title: Blood of the Isles)
Tidy Neanderthals? - World Science
Southrn Yemenis in various areas of Africa
Yemeni Families in early 20th-century Addis Abeba

OBJ

Questions initially addressed in reply to an email enquiry 14 March 2009
Essay developed for OJTR 23-24 October 2009
Developed March 2012
Last edited 17 March 2014

Orville Boyd Jenkins, EdD, PhD
Copyright © 2009 Orville Boyd Jenkins
Permission granted for free download and transmission for personal or educational use.  Please give credit and link back.  Other rights reserved.

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