"Peter D'Adamo has either made a very significant contribution to the study of human dietetics, or he has revolutionized the field of nutritional medicine."

-Jonathan Wright, M.D.

Advanced Topics in Blood Type Diet



Copyright 1955 Abelard-Schumann, New York


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 1950'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-à-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


It is quite common to hear people talk of blood as though it differed according to race or nationality. You may have heard talk of "Negro blood" or "French blood" or even "Jones blood' or "Smith blood." During World War II some people wanted the American Red Cross to keep the blood it received from white people separate from that which it received from Negroes. Supposedly this was to keep white soldiers from receiving transfusions of "Negro blood."

Actually, this is nonsense and superstition. If a scientist or a doctor were given a sample of normal blood, there would be no way in the world be could determine for sure whether it came from a man or a woman, a Frenchman or a German, a Negro, an Aboriginal, a Chinese, or an American. Nor could your body, if the blood were put into your veins.

Yet there are ways in which your blood may be different from your neighbor's, or even from the blood of your closest relatives. Let us see how.

Every once in a while, during an operation or as a result of a serious wound, a man or woman may suffer considerable loss of blood. To keep the patient alive, it is sometimes necessary, then, to transfer blood into his body from that of some healthy person (called a donor) who is willing to give his or her blood for the purpose. (A person in normal health can easily give up a pint of blood without pain or any harmful effect. The body quickly manufactures new blood to replace that much.)

Such a transfer of blood is called a transfusion.

When a patient needs a quick transfusion of blood, it is not enough just to grab any healthy person as the donor. The blood of one donor may save the patient's life. The blood of another, equally strong and healthy, may kill the patient. The use of a relative as a blood donor is no insurance. The blood of the patient's own mother or sister may be deadly, while the blood of a complete stranger, of a foreigner, or of a member of a different race, may be life-saving.

Why is this so? Let's consider blood a bit more closely.

The liquid portion of blood is called plasma. Plasma is mostly water, but it contains many dissolved substances of great importance to body chemistry. Floating in the plasma are various kinds of cells. The most numerous of these cells are the red cells, which are also called erythrocytes. These are very small and simple cells. They are so simple that they do not even contain nuclei. The erythrocytes are the only human cells which do not contain nuclei.

The erythrocytes do contain small quantities of certain chemicals known as blood-group substances. Two important kinds of blood-group substances are referred to simply as A and B. In any one person, all the erythrocytes are alike in the kind of blood-group substances they contain. In one case, perhaps, all the erythrocytes contain A, and none of them contain B. A person with such erythrocytes is said to possess blood type A.

In the plasma of a person of blood type A there is dissolved a substance that has no effect on A. However, if that substance in the plasma were to come in contact with erythrocytes containing B, it would combine with those erythrocytes and make them clump together in one large sticky mess. The substance in the plasma is therefore called anti-B. Anti-B is said to agglutinate erythrocytes containing B.

On the other hand, a person of blood type B has a substance dissolved in his plasma, which will agglutinate erythrocytes containing A. It is called anti-A.

We have now described two types of people. One kind has A in his erythrocytes and anti-B in his plasma (the two always go together). The other kind has B in his erythrocytes and anti-A in his plasma.

Suppose, now, a patient who is of blood type A needs blood quickly. A healthy volunteer offers his blood. He is also of blood type A. The donor's blood mingles with the patient's without any bad effect, and the patient's life may be saved.

But suppose the healthy volunteer is of type B. As his blood entered the patient's veins, the anti-B in the patient's Plasma would quickly agglutinate the B containing erythrocytes of the donor. The patient would get no good out of such a transfusion. In fact, the resulting clumped-up erythrocytes in his blood vessels would probably kill him.

The same trouble would result if one were to pump type A blood into a patient whose blood was of type B.

There is a third type of blood. Each erythrocyte of some persons may contain both A and B. Such persons are said to have blood type AB. A person of blood type AB has neither anti-A nor anti-B in his plasma. (If he did have anti-A or anti-B, he would agglutinate his own blood and die.) Do you see what this means? Without anti-A or anti-B, he can be given blood not only from a donor of type AB, but also from a donor of type A or B. (Of course, donors of type A and type B have anti-B and anti-A in their plasma, which could agglutinate the patient's AB erythrocytes. This is rarely serious, however. It is the donor's erythrocytes that make trouble. If they are not agglutinated by the patient's plasma, then all is well.)

Blood from a donor of type AB can't be given to a patient of type A, for the B in the donor's erythrocytes causes them to be agglutinated by the anti-B in the patient's plasma. The AB donor isn't good for a patient of type B, either, for the A in the donor's erythrocytes causes them to be agglutinated by the anti-A in the patient's plasma.

In other words, an AB donor can give blood only to another AB, but an AB patient can take blood from anyone.

There is still a fourth type of blood. A person may have erythrocytes containing neither A nor B. He is said to be of blood type O. Such a person has plasma that contains both anti-A and anti-B. He can't accept blood from anyone but another O. On the other hand, since his erythrocytes contain neither A nor B and so can't make trouble, he can give his blood to a person of any blood type. He is a universal donor.

Sometimes it is only necessary to give the patient plasma, and that makes things simpler. Plasma contains A and B, but only in solution; there are no cells to be agglutinated. Furthermore, if the plasma of several donors is mixed, the B in one counteracts the anti-B in another and the A in one counteracts the anti-A in another. It is generally true, then, that plasma can be transferred from any donor to any patient. It is when whole blood (plasma plus cells) is needed that the rules of transfusion must be observed.


A single gene series controls the production of the blood-group substances we have mentioned. Whether a person is of blood type A, B, AB, or O depends on the nature of the genes of that series which he has inherited. Every person has two genes of that gene series, one on each of a pair of chromosomes. He inherits one gene from his father and one from his mother.

Three types of homozygotes are possible among these blood groups. A person can be homozygous with respect to blood group A; that is, he can carry an A gene on both the chromosomes involved. Let's call him AA. A person can have a B gene on both chromosomes or an O gene. He would then be BB or OO.

The gene for A is dominant over the gene for O. Suppose, for instance, that a man who is homozygous for blood type A marries a woman who is homozygous for blood type O. The man will produce sperm cells which will all carry the A gene. The woman will produce egg cells that will all carry the O gene. Any fertilized ovum will therefore possess one A gene and one O gene. All the children of such a marriage will be heterozygous. We can call them AO.

Since A is dominant over O, only the A will appear when scientists test the blood. An AO person will be classified as belonging to blood type A. (Here is a case where a mother is of blood type O and all her children are of blood type A. The children could not give blood to their own mother, but any stranger of blood type O could.)

Suppose a person is of blood type A. Is there any way of telling whether he is homozygous (that is AA) or heterozygous (that is, AO)? The only way one can sometimes tell is by considering the man's children. We have already said that a marriage between an AA and an OO produces children that are all of blood type A.

Suppose, however, that an AO man marries an OO woman. Half of the man's sperm cells contain an A gene and half contain an O gene. All the woman's egg cells contain O genes. You can see that the fertilized eggs could be either AO or OO. In the first case the child would be of blood type A; in the second case he would be of blood type O.

So, you see, if a person of blood type A marries a person of blood type O and has even one child of blood type O, we have found out something. We have discovered that the person of blood type A is AO and not AA. If he were AA, children of blood type O would be impossible.

Of course, as we have just said, an AO-OO marriage can produce either AO or OO fertilized ova. Suppose, just by chance, that all the children produced in the marriage happened to be AO. Here you would have a case where all the children were of blood type A; yet you couldn't be sure that the parent of blood type A was AA, In other words, you can be guided by the type of children produced in a marriage sometimes, but not always.

The gene for blood type B is also dominant over the gene for blood type O. This means that people who are BO are of blood type B. Blood tests cannot tell the difference between BO and BB. The difference shows up (sometimes, not always) in the blood types of the children of such people.

Neither the gene for blood type A nor the gene for blood type B is dominant over the other. Here is a case of incomplete dominance. If an AA person marries a BB person, all the children are AB.

We can now summarize the state of affairs in connection with these blood groups.

1. All people of blood type O are homozygous. They have two O genes. You can see that this must be true. If they had one A gene or one B gene, they would no longer be of blood type O.

2. People of blood type A fall into two groups. They can be homozygous, having two A genes, or they can be heterozygous, having one A gene and one O gene. For transfusion the difference doesn't matter. AA blood and AO blood behave exactly alike in transfusion.

3. People of blood type B fall into two groups. They can be homozygous, having two B genes, or they can be heterozygous, having one B gene and one O gene. In transfusion the two groups behave the same.

4. People of blood type AB are all heterozygous. They carry one A gene and one B gene.


By now you can see one very practical use for blood groups. Suppose some mother had the notion that the hospital had accidentally got her baby mixed up with another baby. She might find out whether this was so by having her blood and the baby's blood tested.

You'll remember, perhaps, that King Solomon, in the Bible, found it necessary once to decide which of two women was the mother of a child. His decision in that matter is the most famous example of the "wisdom of Solomon." With modern blood-group tests the problem might have been very easy.

Suppose, for instance, that one of the women facing Solomon was of blood type O. She would then have two O genes. Suppose that the other woman was of blood type A. She could be either AA or AO. Now what if the child were of blood type AB? it would have one A gene inherited from one parent and one B gene inherited from the other parent. But the woman of blood type O possesses neither an A gene nor a B gene to pass on to the child, and she could not possibly be the mother. The woman of blood type A could be the mother. (Of course, if both mothers were of blood type A, blood tests involving only this gene series would not help.)

In modern times, a woman of blood type O, bringing home a child of blood type AB from the hospital, would know that the hospital must have mixed up her baby with another's. (Such mix-ups rarely happen.)

Blood tests may also be helpful in deciding whether a certain man is the father of a certain child.

Suppose a man and his wife are both of blood type O. Both must possess two O genes. Now suppose that one of their children turns out to be of blood type A. Immediately one can see that something is wrong, for the A gene could not have come 'from the child's supposed parents. It doesn't I t matter whether the child is AA or AO. It must have at least one A gene, and neither its father nor its mother could have supplied it.

In that case either the supposed mother is not the real mother or the supposed father is not the real father. (Or perhaps neither parent is the real parent.)

Suppose, though, that the child turns out to be of blood group O, like both its parents. Does that prove the child is really theirs? It doesn't. It shows the child might be theirs, but it doesn't prove it is. The hospital might have mixed it up with another O-type baby. Or the real father might also be of blood group O.

We can make a general rule. A blood test can prove a supposed parent is not the real parent. It cannot prove a supposed parent is the real parent.

Unless a blood test proves that a supposed parent is not the real parent, it is inconclusive. A decision must then be reached by other types of evidence.

You know enough already to take other cases and see for yourself which blood types are possible among the children of a marriage and which are not. If the father is of blood type O and the mother is of blood type AB, then all the sperm cells carry the O gene, while half of the egg cells carry the A gene and half the B gene. The fertilized ova can only be either AO or BO. It follows that the children of such a marriage must be either of blood type A or of blood type B. Children of blood type O or blood type AB are impossible. This is an interesting case because it is one in which it is impossible for children to be exactly like either their mother or their father in this physical characteristic.

Here is another interesting case. Suppose the father is of blood type A and the mother of blood type B. The father might be AA or AO; it would be impossible to tell which. The mother might be BB or BO; again impossible to tell which. Suppose they were AO and BO. In that case half of the sperm cells would carry the A gene and half the O gene. Half of the egg cells would carry the B gene and half the O gene. The fertilized ova could possess any of these combinations of genes:

OO (blood type O), AO (blood type A), BO (blood type B), and AB (blood type AB)

So you see that, if one parent is of blood type A and the other of blood type B, the children could belong to any of the four types. It would be impossible to prove that any child at all did not belong to this couple if only this gene series were considered.


It is not necessary to give up in despair over this A-B marriage we have just discussed. The scientist who tests blood is not at the end of his rope. There are two varieties of A, called A1, and A2, and these can be told apart by careful testing. This may help in making the decision. (As far as transfusions are concerned, it doesn't matter which variety is present in either donor or patient.)

Then, too, there are other blood-group substances in the erythrocytes which are controlled by different gene series altogether. They are inherited completely independently of the A, B, and O genes.

There is, for instance, a gene series controlling the so-called M and N blood-group substances. One gene of that series causes the formation of M, the other of N. Neither is dominant over the other. If you have two of the M genes, you are of blood type M. If you have two of the N genes, you are of blood type N. If you have one of each, you are of blood type MN. (The M and N blood groups are of no importance in transfusion, by the way.)

Now the M and N blood groups have no connection with the A, B, and O blood groups. A person can be of blood type M, N, or MN, regardless of whether he is also of blood type A, B, O, or AB.

Suppose, then, that both parents are of blood type O and so are all their children. Only O genes are involved. But suppose that both parents are also of blood type M and so are all their children except one. That one is of blood type MN. He must have got the N gene somewhere. One or both of the supposed parents can't be the real one.

Still another gene series controls the formation of a number of blood-group substances of the Rh series. (The "Rh" refers to the fact that they were first discovered in experiments with the Rhesus monkey.) There are a large number of genes in this series, and as many as a dozen different Rh types (including some heterozygous ones) can be tested for. These, too, can be used to help decide parentage problems. The more types of blood groups we use, the greater the chance of settling such questions satisfactorily.

There are difficulties, too, of course. The methods used to test for the different blood groups can be quite complicated, especially in the case of Rh. It is necessary to understand the exact way in which all the various Rh genes can be inherited. It is also necessary to be certain that you have the proper chemicals to work with. (The most important chemicals are in the liquid portion of clotted blood, called serum, obtained from certain people or animals. It is sometimes a very delicate matter to determine whether the serum being used is just right for the purpose.) To run blood tests properly, an experienced laboratory man is required, and there are not very many of those.

Blood tests, by the way, can also be used in murder cases. It is possible to tell whether a blood stain is human or not. If it is human blood, one can sometimes tell whether it is of the same blood type as that of the murdered man. Even ancient Egyptian mummies have been successfully tested for blood type.

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