Panel 1: All relatives, everyone different
A single species and more than 6 billion unique men and women
The 6 billion human beings who today inhabit the earth are very different from one another.
However, despite these differences, there are no biological barriers between them. All the men
and women of the world could have children together and their children, in turn, could have
their own children. We all belong to the same, single, biological community --- the human species.
This exposition presents some results from scientific research on both the diversity and the unity
of our species. It invites you to discover why (and how) we are, at the same time, all related
and each unique.
[Credits] These 18 posters constitute an abridged version of the exposition "Tous Parents,
Tous Diff�rents" originally presented at the Mus�e de l'Hommes in Paris and produced by the
Laboratory of Biological Anthropology of the University of Geneva in Switzerland.
A version of it was also shown in the Museum of Natural History in Geneva, Switzerland,
-of the Ministry of Higher Education and Research (DISB)
-of the Fund for social action for immigrant workers (FAS)
-of the Ministry of Culture and the French Language
-of the National Institute for Health and Medical Research
-of the University of Geneva
-of the Swiss National Fund for Scientific Research
-of the Society of Friends of the Mus�e de l'Homme of the National Center for ScientificResearch
To all these we acknowledge a large Thank You.
The American version of this exhibition was produced by Ninian Hubert van Blyenbourg,
in collaboration with Marshall H. Segall, with support from Syracuse University's Office of
Student Affairs and the College of
Arts and Sciences and had its first American showing on the campus of Syracuse University.
Panel 2: Let's get undressed!
In this exposition, we leave our culture in the cloakroom.
In the course of 100,000 years of human destiny, our ancestors diversified physically and they also developed different cultures. Today there exists an extraordinary wealth of clothing styles, hair styles, languages, religions, ideologies, social organizations, and technological inventions. Some of these man-made differences are probably responsible for some of the effectively real cultural barriers between some human groups.
Our cultural characteristics are not determined at birth. We assimilate them and accommodate to them in the course of our lives. They are transmitted from generation to generation by learning and education. Accordingly, any individual person whosoever, from birth onward, can acquire any culture whatsoever.
Our considerable physical diversity, unlike our cultural characteristics, reflect physical traits inherited from our biological parents at the moment of our conception.
In this exposition, we are interested only in our genetic, or biological, diversity. We are concerned only with the human body and its constituent parts.
So, we leave our culture in the cloakroom.
Panel 3: Our visible diversity
Our species presents more differences in body forms and colors than any other species.
Some of these visible differences are scarcely perceptible, while others like stature
(standing height), skin color, and face shape, vary markedly from one group of
individuals to another.
Panel 4: Height
The average heights of human groups can be shown to relate to the diverse environments they
The study of heights the world over shows that "tall", "average" and "short" people are found on
all five continents. This distribution is the result of our ancestors' adaptation during the
prehistoric era to the very different environments they came to inhabit. (One visual in this
panel shows average male heights in the world before the great migrations which began circa 1492.)
Short people tend to be found in tropical forests (e.g., Pygmies in Africa) or in polar environments (e.g., Eskimos in North America).
Tall people tend to be found in cool, temperate zones (e.g., Swedes of Europe) or in hot desert climes (e.g., the Masai of eastern Africa).
A comparison of two populations of different average height shows an average height of 175.2 centimeters (cm.) for 99 Frenchmen and an average height of 157.9 cm. for 116 Quechwas. (This is a mean difference of 7.3 centimeters.) However, each of the two distributions show more than a 20 cm. range from shortest to tallest within the groups and some individuals from both groups occupy the range from 160 cm. to 170 cm. This overlapping range includes 47 Quechwas and 34 Frenchmen (approximately one-third of the individuals in both groups). Within this range, the shorter members of the "tall" group are shorter than the taller members of the "short" group.
Whatever physical characteristics we might choose, our study mandates two assertions:
- No physical characteristic ever changes brusquely from one population to another.
- Any physical characteristic always varies a great deal among individuals in the same population.
Panel 5: Skin color
The average skin color of a human population relates to its latitude of origin; the closer to the Equator, the darker the skin color.
The coloration of our skin is due to a single brown substance called melanin (which is made by certain epidermal cells called melanocytes) which protects skin against the ultra violet rays of the sun. The more or less dark color of a person is determined by the amount of melanin present in the deep recesses of the epidermis. Blood can add, via transparency, a reddish or bluish nuance.
Two cross-sections, one of light skinned peoples (e.g., Eskimos, Chinese, and Europeans) and one of dark skinned peoples (e.g., West Africans, Sri Lankens, and Oceanian) show many more grains of melanin in the latter groups.
The distribution of average skin color of groups across the world prior to the great
migrations shows that darker-skinned populations came from the inter-tropical zones of
all the continents. The lighter populations originated in the cooler temperate regions.
Environmental adaptations, undoubtedly independent in the various geographic regions, brought about the distribution of this characteristic during the prehistoric era.
The distribution visual shows, for example, that Indians from the north of North America and from the south of South America are both lighter skinned than the Indians of Central America. Yet, all these populations are descended from the same ancestors who peopled the Americas from North Asia in the course of pre-history. Only one or two dozen millennia were enough to modify this physical aspect of these populations.
In summary, the entire human population comprises a great diversity of skin color. Arraying end to end the gradations of color of only four selected populations (Saras from Chad, Sans from South Africa, Chaouias from Algeria, and Belgians from Belgium) results in a continuous range from so-called 'Black" to so-called "White". This array also shows that some individuals from any two adjacent groups share skin color. There are no distinct categories of skin color; rather a continuous variation which ranges from the darkest individuals in the darkest populations to the lightest individuals in the lightest populations.
Panel 6: The perception of diversity
Physical diversity is everywhere infinite.
Certain important contrasts among human populations lead to our easily underestimating our true diversity. This is evident especially in cross-population perception. A European often has the impression that "the Chinese" or "the Africans" are "all alike". (A Chinese person may have the same impression of Europeans.)
This faulty perceptual habit creates an image of diminished human diversity. This is due to our lack of experience in learning how to identify people who are physically different from us. In fact, faces everywhere, within every human group, are equally different one from the other. If this were not the case, how then is it possible for people everywhere to recognize a familiar person in a crowd of unknowns?
There are four famous people in a set of 18 portraits. Find them!
Panel 7: The sameness of human bodies everywhere
At the level of physiological details, each individual is constructed of the same elements.
Our physical differences must not lead us to forget that we are all built in the same way, of the same elements. Our organs vary in size and shape, but these small variations do not affect their functioning at all. (Only our sex organs present important differences --- between men and women.)
550 million pulmonary cells -- equivalent to about half a football field
4.5 square meters of skin
100 billion white blood cells
25,000 billion red blood cells -- equivalent to a 550 square meter surface.
800 diverse tissues
10,000 billion nerve cells, representing a total mass of 2.2. kilograms
950 kilometers of blood vessels, through which 5 liters of blood circulates
100 or so organs,
450 pairs of motor muscles,
and all involving 60,000 billion of cells, the basic building blocks of our bodies.
Panel 8: Invisible diversity
Human beings differ not only in their physical appearance, but also with respect to invisible characteristics.
Although everyone's blood has the same appearance, we know that certain rules have to be observed in order to perform blood transfusions. They are possible only when the blood types of donor and receiver are compatible. Thus, humans are not only superficially different, they also differ in these "invisible" respects.
We know that there are four principal blood groups ..... A, B, AB, and O. For a transfusion between two people to be possible, there must be compatibility of blood types. However, the blood of a Mahgrebian or of a Senagalese can save the life of a Vietnamese or of a French man or woman, just so long as they possess compatible blood types.
The origins and physical appearances of the donors and recipients are totally irrelevant.
( A visual shows the distribution of blood groups A,B,O, and AB in 73 populations.)
With a few minor exceptions, the 4 blood groups are found in all human populations. Therefore, there is obviously no relation between blood group and the physical traits of a person.
(A visual shows people of varying physical appearances in different parts of the world, with arrows depicting possible blood transfusions.)
By following the arrows which indicate which persons can give blood to which other persons, construct the rules for compatibility.
An individual in blood group A can give his blood to individuals in blood group A or AB.An individual in group B can give his blood to individuals in groups B or AB.An individual in group AB cannot give his blood to another individual in group AB.An individual in group O can give his blood to everyone in all the blood groups.
Panel 9: The bases of difference
Our biological diversity is determined genetically.
Like one's physical appearance, one's invisible characteristics are determined by our "genetic baggage" inherited from one's parents. And, while we do not know the genes which determine skin color, height, or facial type, we do know the genes which determine characteristics like blood type or the Rh (Rhesus) factor.
What is a gene? (Illustrated by 5 visuals)
A human body is composed of approximately 60,000,000,000,000 (60,000 billion) cells.
Each cell contains a nucleus.Each nucleus contains a genetic baggage of 46 hromosomes.
Each chromosome is a filament composed of a chemical substance called DNA.A gene is a fragment of DNA, containing all the necessary information to determine a characteristic.
Each human being has 46 chromosomes in its cells. Since we receive 23 from our mother and 23 from our father, we each have 23 pairs of chromosomes. This double origin of our chromosomes explains why we always possess two exemplars of each gene (with the exception of certain genes carried by the sexual chromosomes). The genes which determine, respectively, blood group ABO, the Rh factor, and the HLA group are localized on the chromosome pairs 9, 1, and 6. (Illustrated)
Panel 10: The genetic variants
There are thousand of variable genetic characteristics. The combination of their variants underlies genetic diversity.
Research on genetic inheritance has demonstrated that we all have the same genes, but that the chemical composition of our genes varies from one to the other. It is this variation which makes all individuals unique. We also know that everyone possesses two exemplars of each gene. For the same gene, there are thus potentially as many different types of individuals as combining the variants two at a time allows.
(The visual provides three examples .... ABO, Rh, and HLA ... showing for each the number of variants in genes and the possible number of different individuals)
The ABO blood groups
The ABO blood groups constitute the best known example of genetic diversity.
The ABO gene exists in 3 variants, which, when combined 2 by 2, can form (in 4 groups) 6 types of individuals. (Illustrated: AA, A0, BB, BO, AB, OO)
The Rhesus factor
Sometimes responsible for an incompatibility between the blood of a mother and that of the fetus she is carrying, the Rh factor is another well-known example of genetic diversity.
The Rhesus gene exists in 2 variants (+, -), which, when combined 2 by 2, can from (in 2 groups) 3 sorts of individuals. (Illustrated: ++, +-, --).
The HLA groups
HLA (Human Leukocyte Antigen) groups are not very well known, but they play a determining role in the phenomenon of acceptance/rejection of organ transplants.*
The HLA group of a person is detrained by the combination of 6 genes HLA- A, - B, -C, -DR, -DQ, and -DP, each of which has a large number of variants.
Thus, the number of different HLA groups is enormous.
The HLA-A gene has 41 variants, which can form 861 individual types;
The HLA-B gene has 61 varaints, which can form 1,891 individual types;
The HLA-C gene has 18 variants, which can form 171 individual types;
The HLA-DR gene has 60 variants, which can form 1,830 individual types;
The HLA-DQ gene has 19 variants, which can form 190 individual types;
The HLA-DP gene has 38 variants, which can form 741 individual types.
The more numerous the genetic variants, the greater the number of possible individual types for any given genetic system. With respect to the totality of HLA groups, t is impossible to depict them all on a graphic.
* An addendum regarding HLA groups:
Two individuals who possess the same HLA groups can, if necessary, exchange their organs unproblematically. There will be no rejection. Two persons having different HLA groups can exchange their organs only under certain conditions and must undergo an anti-reject medical procedure. As in the case of blood transfusions, the possibility of organ transplant does not depend on any superficial physical aspect of donor and receiver, but only on the compatibility of their HLA groups.
Incidentally, one of the first heart transplants was done in South Africa between a so-called "Colored" and a so-called "White" by the surgeon Christian Bernard. This was in 1967. From that early date onward, there was no apartheid between the hearts in South Africa!
Panel 11: Individuals pass away/Genes are passed on
Transmitted from one generation to another, genes bear witness to our relationships of parentage.
We inherit our genes from our parents who, themselves, received them from our grand-parents. In their turn, our grand-parents in herited their genes from our great grand-parents, who, themselves, received them from our great great grand-parents.
Thus, from the dim recesses of time, our genetic heritage has been transmitted from generation to generation, according to the principles of genetic transmission. From this, genes constitute evidence of the lines of relationship.
(Graphic shows a six generation family tree, with portraits of individuals.)
The symbols placed under the portraits of these members of the same family represent the two variants of ABO and Rhesus that they have inherited from their parents.
Panel 12: Same genes = Same ancestors
World-wide research on genetic diversity shows that all human populations possess practically the same genetic variants; we all have the same ancestors!
(Graphic shows Proportions in 18 contemporary human populations of gene variations for ABO, Rh, and HLA-A.)
The 18 population studied here possess practically the same variants in ABO, Rh, and HLA-A, but not in the same proportions. (Occasionally, certain variants appear absent in certain populations, but this is often attributable to too small sample size.) This fact applies practically to all genetic characteristics.
Since genes are transmitted from generation to generation and since the same genes are found in widely separated populations, it must be concluded that all humans alive today are descended from common ancestors.
Panel 13: Genetic diversity and migrations
The genetic diversity of contemporary human populations reflects the paths followed by our ancestors in the course of their world-wide movements.
All human populations posses practically the same genetic variants, but the proportions vary from one population to another. In studying differences between two populations, we get a measure of their genetic resemblance; to the degree that these differences are minor, the more the two populations resemble each other genetically.
(The graphic shows genetic resemblance via bars; bar length indicates degree of genetic closeness.)
The genetic network resulting from a comparison of 19 populations spread over the 5 continents shows that genetic diversity changes progressively from one population to another, as a function of continental geography. This proves that the diversity results from displacements made by our ancestors following their "conquest" of the world and the migrations which followed.
The genetic network
The numbers placed beside the bars express a percentage of genetic relationship between two populations. These percentages were obtained by comparing the proportion of genetic variants of three characteristics ... Rhesus, HLA, and GM (another genetic characteristic related to the body's immune system) ... of the 19 populations.
Racial classifications are arbitrary
An illustration, a page reproduced from a 19th century work (Anthropogenie by Ernst Haekel, 1871), shows that our contemporary understanding of human diversity differs fundamentally from the racial classifications of yesteryear.
Those classifications were not only arbitrary and full of prejudices (note the Germans placed at the top and Africans at the bottom, adjacent to "primitive men" and "monkey men"), but they involve a notion of a hierarchical relationship of groups. On the contrary, the genetic network shows no boundaries between populations and a linkage among them, that is uniquely a function of their geographic separation.
Panel 14: Humans like us over a span of 100,000 years
The history of our species began "only" 100,000 years ago, with the appearance of "modern man" (Homo Sapiens Sapiens).
Archeological remains of the most ancient people like us have been found in the Middle East and Africa. Therefore, it is most probable that it was in this region of the world that our first direct ancestors lived. The dating of these first "humans like us" places them about 100,000 years ago. Our species is, therefore, very young, if one compares its age with the duration of human evolution, begun about 3 million years ago with the first uncontested tool-makers, Homo habilis.
(Graphic shows 3 categories ... upright apes, humans not like us, and humans like us.)
Homo erectus, Homo habilis and Neanderthal man differ so much from contemporary humans that they cannot be considered human like us. The Australopithicus are so different from us that one usually refers to them as upright apes.
Humans like us
(Graphic contains a map showing the locations of the fossil findings of modern man.)
What is a human like us?
Archeologists consider a skeleton that does not differ from one of a contemporary man or woman a skeleton of a Homo Sapiens Sapiens. The skeleton of the prehistoric Qafzeh Man, found in Palestine, fits this definition. Dating from approximately 100,000 years ago, it is one of the oldest known "modern men".
If the Qafzeh Man lived today, we could establish that he didn't differ from us. He would surely pass unnoticed in a crowd. His intellectual capacities were, doubtless, comparable to ours and he would probably have been able to benefit from the same kind of education we receive.
Panel 15: The peopling of the world
We are all immigrants!
The populating of the planet by our ancestors was accomplished progressively outward from a region situated between the Middle East, North Africa, and East Africa. Thus, all contemporary human beings are descended from immigrants. For example, as shown on one of the maps on this panel, France was occupied by modern men for the first time about 40,000 years ago. Cro-Magnon Men, who were the first known modern "Frenchmen", were the first immigrants to come to France from the Middle East.
(Graphic maps show the peopling of the world over 100,000 years).
1. 150,000 to 100,000 years ago: the appearance of the first modern men.
2. 60,000 to 50,000 years ago: the peopling of North Africa, South-East Asia, and Oceania.
3. 40,000 years ago: the peopling of Europe, Central Asia, and China.
4. 30,000 years ago: the peopling of Siberia and Japan. The establishment of the ancestors of contemporary Africans.
5. 20,000 years ago: the peopling of eastern Siberia and of the Pacific rim of North America.
6. 10,000 years ago: the spread of people over the Americas.
7. 6,000 years ago: the peopling of Northern Europe, the northern reaches of Alaska and Canada and the peopling of Central and Southern Africa.
8. From 5,000 years ago to the tenth century AD : the peopling of Micronesia, Polynesia, New Zealand and Madagascar. The last population move...into Greenland.
Panel 16: The illusion of race
It is an illusion that there are races. The diversity of human beings is so great and so complicated that it is impossible to classify the 5.5 billions of individuals into discrete "races".
Some of our physical differences give the impression that it is possible to divide us into races. But when these physical characteristics are subjected to detailed study, that cannot be concluded at all. Instead it becomes obvious that our physical diversity reflects continuous changes from one extreme to the other of the continents (refine). To place any boundaries within this continuous diversity would be, therefore, completely arbitrary. Human diversity is in fact infinitely more complicated than the idea we have constructed of it. This is why attempts to make racial classifications don't yield any coherent results; there is nothing scientific about "races".
The science of genetics teaches us that it is impossible to attribute physical resemblance to genetic resemblance.
As the genetic network shows, the populations of Africa and of Melanesia, who very much physically resemble each other, are genetically very far apart. Inversely, Melanesian and Oriental populations, genetically very similar, differ very much from each other in their physical traits.
The idea that it is impossible to classify us is not new. As early as 1784, the German philosopher and naturalist, Herder, concluded, "There exist neither four nor five human races ... The term race refers to a difference of origin which is non-existent for humans ... All physical types are inter-twined and follow hereditary characteristics ... and in the end are only the shadows of a single large picture which extends through all the ages and over all the continents."
We had to wait for contemporary genetics to finally recognize the modernity of this two hundred year old idea.
Panel 17: All of us related .....
We all share the same ancestors multiple times.
As we know, thanks to our genes, we all have the same ancestors. But the awareness of our ancestors is limited to a few generations; consequently, we have great difficulty believing that all of us in the world are all more or less attached. However, by comparing a hypothetical number of unique ancestors to the number of human beings that have really existed throughout the course of human life, we can better understand how we are all, inevitably and necessarily, related.
1. Any one of us has two parents, 4 grandparents, 8 great grandparents, 16 great great grandparents, etc.
2. Following this formula to seven generations back, which takes us approximately to the year 1800 AD, each one of us has 128 ancestors. (2,4,8,16,32,64,128 or 2 to the seventh power)
3. If we extend this logic back to the beginning of the Christian era (1 AD) each of us would need to have had 1 million billion billion (10 to the 24th power) ancestors. If the 5.5. billion people alive today each had a unique set of ancestors, there would have to have been 5.5 million billion billion (10 to the 33rd power) of ancestors for all of us.
4. The problem with the prior argument, however, is that there were only a few hundred millions of people on the earth at that time. Indeed, the world's population didn't reach one billion until approximately 1800 AD.
5. Hence the reality is that 5.5 billion people alive today share, over and over again, the same ancestors. Our forefathers (and foremothers) married their relatives, often without being aware of it, simply because early people were very few in number, a few million at most.
Because all individuals have some common ancestors, we are all necessarily relatives!
That is the reality for all human beings alive today.
Panel 18: ........Each of us unique.
It is estimated that 80 billion human beings have lived on Earth over the time since our common origin. With the exception of true identical twins, never have any two among them have had exactly the same genetic heritage. Thus, each is unique.
To each generation, the parents transmit a novel combination of their genetic variants to their children. This "genetic brewing" results theoretically in as many possible individuals as there are combinations of all the genetic characteristics. Applying this logic only to the genetic variants ABO, Rhesus, and ALA, would already produce :
1,291,178,228,421,950,000 different individuals!
(This result is obtained by multiplying the numbers presented on panel 10; viz., 6 x 3 x 861 x 1891 x 171 x 1830 x 190 x 741.)
This colossal number illustrates that merely three genetic characteristics suffice to produce at least 200 million times more unique individuals than actually exist on the Earth today -- approximately 5.5 billion.
Applying this logic to all the variable genetic characteristics of humans, it is easy to show that the number of different possible human individuals is many times greater than the number of atoms in the universe!