In the days before DNA testing how did a "blood test" confirm or disprove paternity?  Not all children have their father's blood type. ?


For example, my wife is O negative.  Neither of her parents are.  

11 Answers

  • 4 months ago

    They did more than just ABO and the RH (there are actually 6 alleles here: CDE and cde) system. They did Kell, Lewis, MN, P, Duffy, etc. then they plotted it all out. Exclusions were fairly easy, the more system matches predicted, the closer it was to inclusion.

  • 4 months ago

    If you and your wife have A or O blood type and the baby is B, you can DISPROVE paternity.  There are perhaps a dozen to two dozen other typing factors, such as Rh+ or Rh-, and the combination of those dozen or so tests can be used to EXCLUDE candidates.  If you watch Maury Povich when he does his paternity test, you would note that he often says the man is excluded from being the father.

  • Anonymous
    4 months ago

    The blood type of a man and a woman can help determine is the man can be the father. It is not as precise as DNA testing, but it is better than nothing. For example, if the father is AA+ and the mother is BB+, and the child is BO+, then the man is almost certainly not the father since the child can only be AB blood type if he is the father. The child's real father is either BO or OO.

  • 4 months ago

    DNA pairing and Blood Group pairing are two different biological terms .

    Blood groups are not having hereditary characteristics but DNA do have !

    There are total 8 main blood types with Rh positive or negative  - 4 of them are common :

    1) A type blood has only A antigens on RBC ( Red Blood Cells )

    2) B type has B antigens

    3) AB has both

    4) O has neither A nor B antigens.

    By the way , people with O blood type have the lowest risk of Heart Diseases !

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  • Anonymous
    4 months ago

    It never confirmed, it just "ruled out" in some cases.

  • User
    Lv 7
    4 months ago



    there are some blood types

    that cannot possibly come from parents of specific other blood types.

    For example:

    two O-blood-type parents

    cannot produce a child with anything other than O-blood-type.

    SO: it doesn't work in all scenarios

    but in some scenarios

    blood type of two supposed parents can prove that the child is NOT the child of that particular pair of people.

  • Zirp
    Lv 7
    4 months ago

    it wasn't a bloodtest. It was a bloodtype-test. Scientists figured out quite soon that A, B and 0 all came from the parents. If both parents were A, the child would not have B, and vice versa. Stuff like that.

    then they tested a whole village and concluded that at least 10 % of the population was not the biological child of the legal father.

    Was cheating that common? maybe not, because later on it was discovered that some people have the alleles for A and B on the same chromosome. This means that one parent with type AB and one with type O can still have AB-children, which was previously considered impossible

    @update: well, that's perfectly possible if both her parents are carriers of the recessive allele for type 0 and the recessive allele for rhesus negative

  • 4 months ago

    Actually, it didn't, for a long time. As I recall, Charlie Chaplin was legally declared the father of a child he could not possibly have fathered.

    There are a few combinations that will not be possible. For example, an AB adult could not be the parent of a type O baby. Two type O parents could not have anything but type O children. Rh- is like type O in this regard. There are also other factors, like the MNO group, that could be tested for.

  • 4 months ago

    Before DNA all a blood test could do is prove you were NOT the father.   If the kid is Type A and the Mother is Type O  and the suspected father is Type O  there is no way that kid could be his.   The father would have to be Type A.   

  • 4 months ago

    It was never considered to be 100% conclusive, as blood-type analysis for any given child can only exclude about 30-40% of the population from being the father.  Of course, if you're in that 30-40%, you are guaranteed to be excluded.  And even 30-40% is better than a pure guess.

    As time went on, comparisons of other things beside blood type (usually serological proteins) dramatically improved exclusion rates.  By the 1960s, they were up to about 80%.


    Re: your example - 

    Two type-O parents can only produce a type-O child.  But type-O children can have other combinations of parents.  For instance, two type-B parents can have either a type-B or a type-O child.

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