A Wiki about biochemical individuality



FROM RACES AND PEOPLE BY William C.Boyd, Ph.D. and Isaac Asimov, Ph.D. Copyright 1955 Abelard-Schumann, New York

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William Clouser Boyd, blood type anthropologist, science fiction writer with Isaac Asimov and the discoverer of lectins (talk about a life!) used his work with blood types in Races and People to demolish the racist notions then commonly believed in this country during the 195O's. This section is on inheritance and constitutes one of the best handlings of a complex subject for the layperson

Fifty years later John H. Jenkins could still write of Races and Peoples:

"Asimov, as an unabashed liberal and champion of the essential value of any human being (partly because of his growing up as a Jew in an era when significant portions of the world found anti-Semitism innocuous or even virtuous), here attacks the notion of "race". He shows how it is hard to define and uses Boyd's research to demonstrate that the superficial characteristics which so many of us use to define "race" and determine our value vis-a-vis other human beings are utterly without value. In the end, again following Boyd, he resorts to blood typing as a method; not to determine race, but to trace the different overall "types" of humanity and show how they have moved back-and-forth across the world. This is truly a book which ought to be read much more today. (I speak as one who has unabashedly absorbed many of Asimov's liberal values.)

Boyd defined race as "not an individual, not a single genotype, but a group of individuals more or less from the same geographical area (a population), usually with a number of identical genes, but in which many different types may occur." For Boyd you got your racial characteristics from where you live more than from your genes, and this explained why the variability made the notions of race untenable.

Peter D'Adamo

The Advantages of Blood Groups

A person's blood group is one of his physical characteristics, just as a dark skin may be, or blue eyes or a hooked nose. Like other physical characteristics, blood groups can be used to divide mankind into races.

You may ask at once: But would they be any better for the purpose than skin color or any of the other physical characteristics we have talked about in this book?

The answer is that in some ways they would be.

  • They are "hidden" characteristics. You can't tell a man's blood group by looking at him. This reserves race classification to scientists who are interested in the development and evolution of man. It keeps a person from making judgments of his own about his neighbor's race and from building up superstitions and prejudices about it.
  • Unlike the more familiar physical characteristics, blood groups are inherited in known ways. The A, B, and O blood groups are controlled by a single gene series consisting of three genes. The M and N blood groups are controlled by a single gene series consisting of two genes. The Rh blood groups are controlled by a single gene series consisting of eight genes. In each case, we know which genes are dominant over which.
  • A man's blood group is determined the instant the fertilized ovum is formed and remains the same till the day he dies. Even after death tissues can be tested for blood groups. Blood groups aren't affected by age or diet or exposure to sunlight or by any kind of chemical or medical treatment. None of the things that affect the physical characteristics usually used to determine race will affect blood groups. Blood groups are permanent.
  • With one exception, which we will mention later in this chapter, blood groups have no drastic effect on the health of a man, the length of his life, when or whom he marries, or the number or health of his children. That means that the blood-group genes are all passed on from generation to generation according to pure chance. Blood groups would therefore show how human beings have mixed with one another, for there would be no confusion due to the workings of natural selection.

The Key Word: Frequency

The simplest situation we could imagine would be to have all people who live in one part of the world belong to blood type O; all people in another part of the world belong to blood type A, and so on. Actually, of course, nothing like this happens at all. The various blood groups are found all over the world. However, they are not found in the same proportions everywhere.

There are some tribes of American Indians in which as many as 98 percent of the people tested are of blood group O. The rest are of blood group A. Other Indian tribes have a great many people of blood group A, some as many as 80 percent of the people. The rest are of blood group O. Few, if any, "Pureblooded" American Indians, however, are of blood type B or AB.

Inhabitants of Asia are more commonly of blood type B than are people who live elsewhere. A group of people in Bengal, India, was tested, and it was found that 4O percent of them were of blood type B. Only 32 percent were of blood type O, and only 2O percent of blood type A. The rest were of blood type AB.

In general, over all the world, blood type O is the most common. Blood type A is next, and blood type B is after that. Blood type AB is the least common. It is very rare for even as many as 10 percent of a population to be of blood type AB.

Scientists try to go further than just the blood types. They try to determine how many of each type of gene are present. For instance, we know that every person of blood group O has two O genes and every person of blood group AB has one A gene and one B gene. However, a person of blood type A may have an O gene or may not. The same is true of a person of blood type B.

Fortunately, there are ways of calculating from blood-group figures how many O genes are hidden in persons of blood groups A and B. (You can't tell which particular persons have them, of course.) Once you've calculated the number of hidden O genes, you can tell exactly what percentage of each gene is present in a particular population.

In this way one determines the gene frequencies in a gene series.

Let's see what we get out of calculating our gene frequencies. Tests on the population of London show that, of the A-B-O gene series, 70 percent are O genes, 25 percent are A genes, and 5 percent are B genes.

In the city of Kharkov, Russia, on the other hand, tests show that of that gene series, 60 percent are O genes, 25 percent are A genes, and 15 percent are B genes.

Suppose that a sample of blood is brought to a scientist and he is told: "This blood is taken from either a Londoner or a Kharkovite. Can you tell me which?" The answer is, "No!" All three types of genes are found in both cities. But suppose a thousand samples of blood are brought, and they come either from a thousand Londoners or from a thousand Kharkovites. Now the scientist has a very good chance of making the right choice, for the gene frequency of B is three times as high in Kharkov as in London. If he gets a small number of blood group B and AB in his samples, they're from London. If he gets a fairly large number, they're from Kharkov.

In fact, if we pick convenient gene series such as that for the blood-group substances, we can have a genetic definition of race as follows: A race is a group hundred and shortly thereafter 25 out of a hundred. The gene frequencies for B are highest in the area surrounded by the isogene for 25 out of a hundred. This area includes central Asia, Manchuria, Iran, and northern India. As you move away from this region in any direction, the gene frequency of blood group B falls off. The areas that are farthest from this region are lowest in B.

(The very low frequency of B in Australia and the Americas applies only to the native population, the Indians and the Aborigines. The Europeans who have emigrated to the Americas and to Australia have the same gene frequencies as their ancestors since they brought the B gene with them.)

When a small area of the world is very carefully and thoroughly studied, a detailed isogene map can be made for it. Such a study has been made in Japan, for instance, and it has been found that the A gene has its highest frequency in an area near the western tip of the country. The frequency is over 30 out of a hundred there. As one travels eastward across Japan, the frequency gradually declines until at the eastern tip it is less than 24 out of a hundred.

Human History By Genes

Now we are ready to see how genetics can help us understand human history.

In the first place, we must understand that the O, A, and B genes are all very old. They are not the result of recent mutations. For one thing, tests on Egyptian mummies show the three blood-group genes to be present there in about the same proportions as in modem Egyptians.

Furthermore, blood-group substances O, A, and B, or substances very like them, are found in gorillas, orangutans, and other apes, as well as in monkeys and lower animals. In fact, when blood technicians want a supply of A substance, they get it out of ground-up hog stomach. Out of ground-up horse stomach they can get something very much like B substance.

It certainly seems, then, that the O, A, and B genes are the general property of many animals, just as the gene for forming melanin is. Mankind has had all three from the very earliest times.

But then, you may wonder, why is it that the Aborigines and American Indians have practically no B gene, and that some Indian tribes have practically no A gene either?

This is no easy matter to solve, and no one has proposed a theory that satisfies everyone.

About the most reasonable theory, so far, is one that supposes that modern man first developed in central Asia at a time when its climate was more favorable than it is now. This earliest group of modern man may have had gene frequencies of 25 A, 15 B, and 60 O out of every hundred A-B-O blood-group genes.

This is about the gene frequency found in central Asia today.

As the population increased, small groups would spread out, looking for new hunting grounds. These small groups would settle down in the new territory and could become the ancestors of large populations eventually.

Now remember that the predictions of probability hold best for large numbers. (We've mentioned this before.) When we say that out of every 100 blood group genes there are 25 A genes, what we really mean is that if a large number of cases are taken, that's how the results will average out.

Suppose you test 500 people, for instance. Each person has two genes of the A-B-O gene series; that makes 1,000 genes altogether. Suppose you find a total of 253 A genes. That's pretty close, since you expect 250 A genes. It's 3 off, but what's 3 in a thousand? Not much.

Suppose you take 50 people, with 100 genes, and find 28 genes for A instead of 25. That's still only 3 off, but 3 in a hundred amounts to more than 3 in a thousand.

Finally, suppose you take 2 persons with 4 blood group genes. You might easily find 4 genes for A. You expect only 1; so you're still only 3 off. But now 3 out of 4 is very important indeed. In fact, it would mean that these 2 persons have only genes for A, no genes for B and O at all.

Therefore, when a small group breaks off from a parent population and goes off to a new territory, it may happen that there is no B gene, let us say, among them. Or there may be a few B genes present, and the owners may happen to die or be killed before they have any children. In either case, you now have a group with only A and O genes. If this group is allowed to remain in isolation, and if no new emigrants from central Asia join them, all their descendants will have only A and O genes.

This is what may actually have happened. From central Asia, separate groups may have reached western Europe, northern Africa, eastern and southern Asia, Australia. None of them would have had any genes for B. Their gene frequencies would have been, say, 30 A and 70 O out of every hundred.

You may ask, "Isn't that too much of a coincidence? Why should it always be the B gene that disappears?" Well, the B gene is the least common to begin with, only 15 out of a hundred. Therefore, in any small group, it is the one that is most likely to disappear.

To go back to our migrating people, imagine now the new inhabitants of northeastern Asia, with only the A gene and O gene among them. They multiply also, and again small groups break away. One such crosses the Bering Strait into Alaska. In this small group, the A gene (which is less than half as common as the O gene among them) either did not exist or happened to die out.

Slowly, the immigrants and their descendants spread throughout the Americas, giving rise to Indian tribes that are almost pure O. Later, other groups, carrying A this time, may have entered Alaska. By modem times, the new groups had only the chance to drift down through North America. For that reason, South American Indians would remain almost entirely O while North American Indians would in some cases have considerable quantities of the A gene.

After that, as we approach closer to historical times and as the human population on Earth increases, there were larger and larger emigrations out of central Asia. These were large enough to carry the B gene with them. The regions that were nearest central Asia, such as Manchuria and northern India, got the most. Eastern Europe got the most in that continent, and the B gene trickles off as you move westward. Northeastern Africa got the most in that continent, and the B gene trickles off as you move westward and southward.

Apparently the first waves of B just reached the northern tip of Australia in quite recent times, and it is only now beginning to drift southward among the Aboriginal population. Peoples carrying the B gene, however never reached the American Indians, until first the Eskimos arrived and later Europeans began migrating into the Americas after the discoveries of Columbus.

The Human Races, By Genes

Suppose, then, that groups of human beings, splitting off from the original central Asian population, had different gene frequencies as far as the A, B, and O blood groups were concerned. It is very likely that the gene frequencies with respect to other physical characteristics were also changed. If these groups multiplied in isolation, they would finally become populations with marked differences in appearance. (This state of affairs is known as genetic drift.) Let us see whether we can detect these different-appearing groups or races, by just considering the A, B, and O blood groups, the M and N, and the Rh blood groups.

The American Indians and the Australian Aborigines are alike in possessing A and O and little or no B. They differ, however, in the M and N genes. Throughout most of the world the frequencies are about 55 M and 45 N out of every hundred. The exceptions are among the American Indians and the Australian Aborigines. The Indians are low in N and high in M; the Aborigines, on the other hand, are low in M and high in N.

The people of Asia and those of Africa generally have higher frequencies of the B gene than other people do. They differ from each other in the Rh series. The Asian peoples have a high frequency of a gene called Rhz to distinguish it from the other genes of the Rh series. The African peoples, on the other hand, have a high frequency of another Rh gene called Rho.

The most troublesome peoples to pin down are those that live in Europe. Here a problem arises in the Rh blood-group series.

In order to explain the problem, let's just say a few words about the Rh series. One of the Rh genes is usually written as rh (with a small "r.") The rh gene is recessive to all the other genes in the Rh series. Therefore, it is only when a person is homozygous for rh (that is, has two rh genes) that it can be detected. Such a person is said to be Rh-negative. A person with only one rh gene or none at all is Rh-positive.

Rh-negative blood is one type that can have a drastic effect on human health. (Remember, we said at the beginning of the chapter that there was one.) Sometimes a mother is Rh-negative and her unborn baby is Rh-positive (having inherited one of the other Rh genes from the father). When this happens, some of the baby's erythrocytes may be destroyed and other serious damage also results. Consequently, the baby will die before birth or very shortly after.

Nowadays, modern medicine can handle these babies, once they are born, by means of transfusions. In earlier times, however, no help was possible. As a result, you would expect the rh gene to disappear slowly. Rh-negative mothers would have fewer living children, and so the rh gene would be passed on less frequently than the other genes in the series.

Sure enough, the American, Australian, and Asiatic groups have little or no rh gene. The African group contains a small quantity of rh gene. The inhabitants of Europe (including Americans and Australians who are descended from Europeans), however, have a good deal of the rh gene; about one out of seven among them is Rh-negative.

Why should this be?

One answer is that there may once have been in Europe a race that was entirely or almost entirely Rh-negative. (That would be safe enough, you see. If everyone were Rh-negative, there would be no problem. It is only when both Rh-positive and Rh-negative are present that the trouble starts.) If there was such an Rh-negative race, then an Rh-positive group may have entered Europe later and intermixed with the earlier group. The one out of seven Rh-negatives in modern Europeans and their descendants would be the result. There may not yet have been time for the rh gene to disappear since the mixture took Place. (And some of the rh genes may have drifted far enough south to show up among the Africans.)

Such an early European race seems to have turned up in the group of people called Basques. These people live in the Pyrenees Mountains (which form the boundary between France and Spain) and adjacent regions. The Basques have interested anthropologists because their language is like no other language in the world. Now it turns out that their blood groups are like no others either. One out of three Basques is Rh negative. This means that the rh gene frequency among them is 6O out of a hundred. The Basques, then, are thought to be descendants of the early race; they hadn't mixed much with the later invaders because they lived in remote mountain fastnesses.

Now we can summarize our six genetic races: ~

1. Australian (Aboriginal): low B or none, low M, no A2

2. American (Indian): low B or none, low N, no A2

3. Asian: High B, high Rhz, no A2

4. African: High B, high Rho, some rh, high A2

5. European: moderately high rh, moderate B, moderate A2

6. Early European: very high rh, no B

~ The genes for O and A are so widespread among all groups of people that they are nearly useless in racial classification.

The six races (plus a seventh race which is less clear-cut) divide the world in an interesting manner. We can follow immigration waves that we could not follow if we used skin color or some other obvious physical characteristic. For instance, a group of immigrants high in A must have entered western Japan from Korea in the not distant past and spread eastward. That would account for the variation of frequency in the A gene in different parts of Japan.

As we learn more about the blood-group genes, and about other genes, too, and as we test more and more people all over the earth, we can expect to be able to trace man's evolution more exactly and to learn the stages by which he has populated the world.