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Thread: Heritability vs Heredity

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    the baby-eater
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    Heritability vs Heredity

    Wiki article if you need a primer (or need to get to sleep in a hurry): https://en.wikipedia.org/wiki/Heritability

    I suspect it's common for people to conflate heritability and heredity (inheritance).

    Heredity is the passing on of traits via genes. (This is the easy one that everyone understands.)
    Heritability is the degree to which genes are responsible for variations in traits.

    Robert Sapolsky gives two examples to illustrate how intuition gets us confused on this:

    1. The heritability of the number of fingers on one of your hands is virtually zero. Variation in the numbers of fingers on your hand is very, very rarely caused by genes. People are most likely to have a different number of fingers due to environmental factors (like using a bandsaw with your eyes closed). (timestamped link to video).

    2. Suppose you have a hypothetical society in which women always wear earrings and men never do. In that society, one's sex chromosomes are 100% responsible for one's earring-wearing behaviour, therefore earring-wearing has 100% heritability. (timestamped link to video)

    This shows that heritability is a completely different idea than heredity, and if we laypersons conflate the two when talking about, say, heritability of IQ in humans, then we are guaranteed to come to the wrong conclusions.

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    Veteran Member James Brown's Avatar
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    So, heredity is that your genes determine who you are, while heritability is that your genes determine what you do.

    Do I have that right?

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    Quote Originally Posted by James Brown View Post
    So, heredity is that your genes determine who you are, while heritability is that your genes determine what you do.

    Do I have that right?
    From Wikipedia:

    Heritability is a statistic used in the fields of breeding and genetics that estimates the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population
    Phenotypic variation means variation in outwardly visible characteristics - hair colour, skin colour, extraversion, size etc. So heritability would measure the degree that this variation was caused by genes.

    Using skin colour as an example we have two extremes - very white and very black. Where you fell on the spectrum of those two extremes would depend on a unique mix of alleles. Roughly, 7 black alleles, 3 white alleles mean you're more black than white. Where 7 white, 3 black might make you light-skinned.

    IOW, skin-colour would have high heritability.

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    Veteran Member James Brown's Avatar
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    Quote Originally Posted by rousseau View Post
    Quote Originally Posted by James Brown View Post
    So, heredity is that your genes determine who you are, while heritability is that your genes determine what you do.

    Do I have that right?
    From Wikipedia:

    Heritability is a statistic used in the fields of breeding and genetics that estimates the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population
    Phenotypic variation means variation in outwardly visible characteristics - hair colour, skin colour, extraversion, size etc. So heritability would measure the degree that this variation was caused by genes.

    Using skin colour as an example we have two extremes - very white and very black. Where you fell on the spectrum of those two extremes would depend on a unique mix of alleles. Roughly, 7 black alleles, 3 white alleles mean you're more black than white. Where 7 white, 3 black might make you light-skinned.

    IOW, skin-colour would have high heritability.
    Then that would differ with bigfield's example of women wearing earrings, wouldn't it?

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    the baby-eater
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    Quote Originally Posted by James Brown View Post
    So, heredity is that your genes determine who you are, while heritability is that your genes determine what you do.

    Do I have that right?
    I don't think it's useful at this point to distinguish between "who you are" (your phenotype, social status etc.) and "what you do" (your behaviour), as both of these are determined by in part by your genes and partly by your environment.

    Some of those traits are passed on to you from your parents. Rousseau's skin colour example is a pretty good example. This is inheritance, or more specifically, Mendelian inheritance (because the trait is passed down in the genes).

    However, inheritance/heredity can coincide with heritability. Skin colour is highly heritable, since it's largely determined by the genes you inherited. However it's not 100% heritable since your skin colour is also determined by your exposure to UV light and your diet. If you wanted to know how much heritability skin colour had in a species, you would need to make sure the test population all ate the same diet and had the same UV exposure. (And make sure no-one gets a spray tan or uses skin whiteners.)

    Heritability determines the extent to which your genes, rather than your environment, make you different from other people. Heredity determines whether or not you can pass on a trait to your offspring..

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    Mazzie Daius fromderinside's Avatar
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    Get the degree. Go to the lab. Conduct the experiments. Write the report.

    Above is the environment one would use those terms. For others it's a parlor game where nobody gains anything. That's especially true for those in the field to which the terms apply.

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    Member Peez's Avatar
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    Quote Originally Posted by fromderinside View Post
    Get the degree. Go to the lab. Conduct the experiments. Write the report.

    Above is the environment one would use those terms. For others it's a parlor game where nobody gains anything. That's especially true for those in the field to which the terms apply.
    Yes and no.

    Behind the technical definitions of these terms are important concepts. Not everyone needs or wants to understand these concepts, but some do. Beyond that it is easy for some people to be carried away when news reports talk about "heritability".

    To the discussion of heritability, I would add the following emphasis: the heritability of a trait is estimated for a population, and depends on the environment the population experiences. In other words, exactly the same trait in two identical populations that experience different environments can have very different heritabilities.

    Peez

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    Formerly Joedad
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    Quote Originally Posted by Peez View Post
    Quote Originally Posted by fromderinside View Post
    Get the degree. Go to the lab. Conduct the experiments. Write the report.

    Above is the environment one would use those terms. For others it's a parlor game where nobody gains anything. That's especially true for those in the field to which the terms apply.
    Yes and no.

    Behind the technical definitions of these terms are important concepts. Not everyone needs or wants to understand these concepts, but some do. Beyond that it is easy for some people to be carried away when news reports talk about "heritability".

    To the discussion of heritability, I would add the following emphasis: the heritability of a trait is estimated for a population, and depends on the environment the population experiences. In other words, exactly the same trait in two identical populations that experience different environments can have very different heritabilities.

    Peez
    Okay, now I want to say that heredity does not require an environment but heritability does. But everything requires an environment so that doesn't work. So when you say "two identical populations" you must mean two genetically identical populations.

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    Member Peez's Avatar
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    Quote Originally Posted by T.G.G. Moogly View Post
    Quote Originally Posted by Peez View Post
    Quote Originally Posted by fromderinside View Post
    Get the degree. Go to the lab. Conduct the experiments. Write the report.

    Above is the environment one would use those terms. For others it's a parlor game where nobody gains anything. That's especially true for those in the field to which the terms apply.
    Yes and no.

    Behind the technical definitions of these terms are important concepts. Not everyone needs or wants to understand these concepts, but some do. Beyond that it is easy for some people to be carried away when news reports talk about "heritability".

    To the discussion of heritability, I would add the following emphasis: the heritability of a trait is estimated for a population, and depends on the environment the population experiences. In other words, exactly the same trait in two identical populations that experience different environments can have very different heritabilities.

    Peez
    Okay, now I want to say that heredity does not require an environment but heritability does. But everything requires an environment so that doesn't work. So when you say "two identical populations" you must mean two genetically identical populations.
    Yes, two populations that are identical in every way except for the environment that they experience. The point I wanted to emphasize is that heritability is not a property of the trait of the organism, it is sensitive to the amount of variability in the trait that is generated by the environment. It is never correct to make a statement like 'brain size has X heritability', without reference to the context.

    Peez

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    Mazzie Daius fromderinside's Avatar
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    Quote Originally Posted by Peez View Post
    Quote Originally Posted by fromderinside View Post
    Get the degree. Go to the lab. Conduct the experiments. Write the report.

    Above is the environment one would use those terms. For others it's a parlor game where nobody gains anything. That's especially true for those in the field to which the terms apply.
    Yes and no.

    Behind the technical definitions of these terms are important concepts. Not everyone needs or wants to understand these concepts, but some do. Beyond that it is easy for some people to be carried away when news reports talk about "heritability".

    To the discussion of heritability, I would add the following emphasis: the heritability of a trait is estimated for a population, and depends on the environment the population experiences. In other words, exactly the same trait in two identical populations that experience different environments can have very different heritabilities.

    Peez
    Maybe you should go back and read the history of Eugenics again. No way for other than sound empirical based study to approach these racist vox populi cast terms in public discussion. ... and the problem stems from those who don't want to understand these concepts. Leave your "you betcha" pal at home when you venture into these concepts otherwise you'll wind up in brown shirt in some swastika parade.

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