The usage of the term blood when speaking about relatives, like blood relatives, blood right, bloodline is not obvious at all, when I start to think about it. I wonder what are the origins of it, namely did people use to think that blood is something that is shared between relatives? To my surprise I have not found any comprehensive treatment of this question on Internet, hence I'm asking it here.

Since this useage is something that is met not only in English, but also e.g. in Latin and many of its derivative languages, I guess it may fit some other community better (perhaps https://linguistics.stackexchange.com/) so feel free to transfer my question where it will better belong. Thank you.

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    As you say, not really an English language question - but, yes, people used to believe that heredity was somehow transmitted in the blood. Sep 11, 2022 at 14:48
  • The blood type of parents directly affects that of their offspring. Sep 11, 2022 at 14:51
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    @YosefBaskin: I'm pretty sure, the usage of this term precedes the discovery of blood types
    – Ilya
    Sep 11, 2022 at 14:53
  • @KateBunting: indeed, my question is - why would they think about blood in particular as a transmitter of kinship
    – Ilya
    Sep 11, 2022 at 14:54
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    @JohnLawler It's true that heredity is contained in the blood, but ironically red blood cells are the one type of cell in the human body which don't show it, in the sense that they lack both nucleus and mitochondria. Sep 12, 2022 at 6:22

2 Answers 2


The origins are in human nature. As you yourself note, blood is used in most languages to describe kinship. Biologically, we are born of the flesh of our parents. Their blood is said to flow in our veins and modern discoveries of genetics and DNA prove that.

Thought.co has an article about kinship and enumerates its types, of which the first is of course:

Consanguineal (of the same blood): This kinship is based on blood—or birth: the relationship between parents and children as well as siblings, says the Sociology Group. This is the most basic and universal type of kinship. Also known as a primary kinship, it involves people who are directly related.

Blood is what it is, and flesh is too. Indeed, in times of old flesh and seed were also used to describe lineage:

...concerning his Son Jesus Christ our Lord, which was made of the seed of David according to the flesh. (Rom. 1:3 KJV)

Blood is described as a means of transmitting filiation and identity in this article:

During the past several decades, historians of Rome have been considering a series of questions raised by anthropologists about the symbolic meanings of bodily humors, especially blood. It is becoming evident that in ancient Rome, bloodthe fluid substance linked with filiation and the transmission of identity—was the object of a set of perceptions much more complex than used to be thought.
(Moreau, Philippe. “The Bilineal Transmission of Blood in Ancient Rome.Blood and Kinship: Matter for Metaphor from Ancient Rome to the Present, edited by Christopher H. Johnson et al., 1st ed., Berghahn Books, 2013, pp. 40–60)

Here is an interesting thread which claims that the origin of the use of blood to describe kinship lies in Aristotle. This may be the answer you are looking for:

We talk about bloodlines and blood relatives because of Aristotle. The short version is that Aristotle believed that semen was a highly purified form of blood, and that menstrual blood was similar but less purified, and the blending of the two resulted in the conception of a child. Since much of Western philosophical and scientific thought centered on Aristotle for many centuries, some of his terminology has stuck long after science has moved past the ideas behind it.

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    Interesting: if by seed they imply male reproductive cells, that would be somewhat earlier than discovery of them causing pregnancy. Also, in case of JC that definitely should not have been the reason according to the Bible. Anyways, thanks for question, but that does not really explain why would blood be used so often, rather than flesh.
    – Ilya
    Sep 11, 2022 at 14:58
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    Me neither, but at least it gives you an idea of the dimensions of the problem: anthropological, sociological, theological, biological, philosophical, etc. etc. It gives you directions for your research.
    – fev
    Sep 11, 2022 at 15:06
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    Definitely. I've upvoted and will accept if nothing more comprehensive appears as an answer. Thanks a lot
    – Ilya
    Sep 11, 2022 at 15:08
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    I have added the link from Google Books for "Blood and Kinship". You can search inside the book, and even read large passages from it.
    – fev
    Sep 11, 2022 at 15:16
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    @Ilya — Knowledge of the relationship between semen and pregnancy seems evident from the Old Testament injunction against spilling one’s seed on the ground. Whether this refers to coitus interruptus or masturbation, it is reasonable to suppose it arose from society’s need for procreation for survival. And to suggest sheep farmers were unaware of this connection…
    – David
    Sep 11, 2022 at 22:54

"Blood" (the fluid matrix, not the specific English word) has historically been related to life and vitality. From the Bible:

"For the life of the flesh is in the blood: and I have given it to you upon the altar to make an atonement for your souls: for it is the blood that maketh an atonement for the soul." Leviticus 17:11 KJV

"Only be sure not to eat the blood, for the blood is the life, and you shall not eat the life with the flesh." Deuteronomy 12:23

I use the Bible as an example here, but blood is considered a sacred fluid across many cultures. It's abundantly clear, even in ancient times, that losing blood directly and immediately relates to loss of life.

"Line" is a word with many definitions. One of which means: "Family; Lineage" (https://www.merriam-webster.com/dictionary/line)

"Blood" (the English word this time) also has many definitions. One of which is: "Human stock or lineage. Broadly: Life." https://www.merriam-webster.com/dictionary/blood

Furthermore, your specific blood type is entirely dependent on the blood type of your parents. If both parents are A, it will be impossible for you to have type B or type AB blood. So there is a certain "passing on" of blood down the family line.

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    Thanks, though it does not answer the origins clearly. Definitely, not the latter point you've mentioned
    – Ilya
    Sep 11, 2022 at 15:27
  • That's fair, I missed you asking specifically about origins so apologies
    – Lemons
    Sep 11, 2022 at 15:36

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