I can't imagine that, for it is always less than one!! .Regards.

Consider a base pair substitution at say a SNP. would this do what you are asking if this was the first occurrence of that mutation. The model I am considering arises from considering a model like that in the attached paper. Best wishes David Booth

This Heritability number can range from 0 (no genetic contribution) to 1 (all differences on a trait reflect genetic variation)

1) Heritability can be greater than 1 due to a greater than expected relatedness between individuals included in the study.

2) Inbreeding in a small population could cause heritability this high.

3) Measurement error can also cause this result

I agree with Rafat's view. I may add absence of sex linked effects, additive x additive interactions,epistasis and highly uniform prevalence of environmental interactions this minimising total phenotypic variance in the denominator ratio. Small SAMPLE SIZEstudied and unreliable standard error of h2 value are the major reasons for this situation to happen

The answers I got from the artificial intelligence of the chatGPT about this:

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is it possible that heritability be more than one?

ChatGPT

No, heritability cannot be more than one. Heritability is a measure that quantifies the proportion of observed variability in a trait within a population that can be attributed to genetic differences among individuals. It is usually expressed as a value between 0 and 1, or as a percentage (0% to 100%).

A heritability of 0 means that the trait is not influenced by genetic factors, and all observed variability is due to environmental factors. A heritability of 1 (or 100%) implies that the trait is entirely determined by genetic factors and has no environmental component.

In practice, heritability values for complex traits in humans and other organisms are typically less than 1. For example, a heritability of 0.5 indicates that 50% of the observed variability in a trait is due to genetic differences, while the remaining 50% is due to environmental factors.

It's important to note that heritability estimates are population-specific and context-dependent. They provide insights into the relative contributions of genetic and environmental factors to the observed variation in a trait within a specific population at a particular point in time.

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but i heard that if there are social interactions, heritability will be more than1. what is your opinion?

ChatGPT

It's not accurate to state that heritability can be more than 1, even in the presence of social interactions. Heritability is a measure that ranges from 0 to 1, representing the proportion of phenotypic variation in a population that can be attributed to genetic differences. A heritability of 1 means that all observed variation is due to genetic factors, while a heritability of 0 means that genetic factors do not contribute to the observed variation at all.

Social interactions and environmental factors can certainly influence the expression of traits, and they are taken into account when estimating heritability. However, heritability values themselves remain bounded between 0 and 1.

It's possible for the heritability of a trait to increase in the presence of gene-environment interaction or social interactions, meaning that the genetic influence on the trait may vary across different environments or social contexts. In such cases, researchers might refer to "context-dependent" or "conditional" heritability. However, these values are still constrained to the 0 to 1 range.

If you've heard statements about heritability being more than 1, it might be a misunderstanding or a miscommunication. It's crucial to interpret heritability estimates carefully and understand the context in which they are presented. It's not a measure of the absolute influence of genes but rather the proportion of phenotypic variation attributed to genetic factors within a specific population and environment.

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" In stark contrast to classical theory, the total heritable variance in a trait can be larger than the phenotypic variance in the trait, Var(TBV) > Var(P)..... In that case, a population contains a heritable variance which is greater than the observed phenotypic variance. Social interactions, therefore, result in hidden heritable variation ".( In book : Julius van der Werf et al. 2009 Adaptation and Fitness in Animal Populations - Page 116 ) Can Piter Bijama's sentence in the book be interpreted in this way: If in the formula heritability, genetic variance is greater than phenotypic variance, the heritability would be greater than one.! What is your response?

ChatGPT

The statement from the book by Julius van der Werf et al. suggests that the total heritable variance (Var(TBV)) can be larger than the phenotypic variance (Var(P)), which might seem counterintuitive at first. However, it's important to understand the terminology and concepts being used in this context.

The total heritable variance (Var(TBV)) refers to the overall genetic variability in a trait, including both additive genetic effects and any non-additive genetic effects (such as gene interactions or dominance). On the other hand, the phenotypic variance (Var(P)) includes all sources of variation, both genetic and environmental.

The key idea in the statement is that, in certain situations with social interactions or gene-environment interactions, there can be hidden or unobserved genetic variation that contributes to the total heritable variance even when the observed phenotypic variance may not fully capture it.

Now, let's address your interpretation of Piter Bijma's sentence. If, in the formula for heritability (h^2), the genetic variance is greater than the phenotypic variance, it would not imply that heritability is greater than one. Heritability is calculated as the ratio of the additive genetic variance to the phenotypic variance (h^2 = Var(A)/Var(P)). The heritability value itself is bound between 0 and 1.

If the additive genetic variance is greater than the phenotypic variance, the heritability would be close to 1, indicating that a large proportion of the phenotypic variance is attributable to genetic factors. However, it would not exceed 1.

In summary, the key point in the book's statement is that the total heritable variance (which includes both additive and non-additive genetic effects) can be larger than the observed phenotypic variance due to hidden or unobserved genetic variation influenced by social interactions or other factors. This does not imply that heritability, as defined by the ratio of additive genetic variance to phenotypic variance, can be greater than 1.

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Sorry, but I'm not satisfied. Small SAMPLE SIZE studied and unreliable standard error of h2 value could be the major reasons for this situation to happen.

ChatGPT

I appreciate your follow-up, and your point is valid. Small sample sizes in genetic studies can indeed lead to unreliable estimates of heritability and inflated standard errors. When sample sizes are small, the estimates of genetic variance may be imprecise, and as a result, heritability estimates can become unstable. This can potentially lead to situations where the estimated heritability appears to be larger than the phenotypic variance.

In statistical terms, the standard error of the heritability estimate is an important factor. The standard error reflects the precision or uncertainty of the estimate. With a small sample size, the standard error tends to be larger, making the estimate less reliable.

It's crucial to interpret heritability estimates in the context of their standard errors and confidence intervals. If the standard error is large relative to the estimate itself, it indicates greater uncertainty in the estimate.

Researchers often emphasize the need for caution when interpreting heritability estimates, especially when sample sizes are limited. Large standard errors and wide confidence intervals should be considered as indicators of the uncertainty associated with the estimate.

In conclusion, small sample sizes and unreliable standard errors can indeed contribute to situations where the estimated heritability appears to be larger than the phenotypic variance. It underscores the importance of using caution when interpreting heritability estimates, especially in studies with limited sample sizes.

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Can be Heritability greater than 1 due to a greater than expected relatedness between individuals included in the study?

ChatGPT

No, heritability cannot be greater than 1, regardless of the relatedness between individuals in a study. Heritability is a measure that ranges from 0 to 1, representing the proportion of phenotypic variance in a trait within a population that is due to genetic differences among individuals. A heritability of 0 means that genetic factors do not contribute to the observed variation, while a heritability of 1 means that all observed variation is due to genetic differences.

The formula for heritability (h²) is:

h2=Genetic Variance/Phenotypic Variance​

The numerator (genetic variance) is always a subset of the denominator (phenotypic variance). Therefore, heritability is constrained between 0 and 1.

Relatedness between individuals in a study can affect the precision of heritability estimates, particularly when estimating heritability through family-based or twin studies. However, even in cases of high relatedness, heritability estimates remain within the 0 to 1 range.

If you encounter situations where the estimated heritability seems unusually high, it's crucial to examine the methodology, sample size, and statistical procedures used. It's also important to consider the possibility of environmental influences and other factors that may affect the interpretation of heritability estimates.