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Population heritability estimates Contributed by Michael Joyner
In the 1800s biometrics, the measurement and classification
of human phenotype, emerged as a field of study.
Early biometric studies showed for example that
parental height could account for about 40% of the variance
seen in children.
As ideas about the biological basis of both between
and within species phenotypic variability emerged
post-Darwin, there has been a long lasting effort to
determine the biological basis of heritability.
This accelerated in the early 1900s with the
rediscovery of Mendel’s work on clearly heritable phenotypic
variation in plants.
It also led to the coining of the terms gene,
genotype and phenotype, and also the discovery of
chromosomes as
the
cellular home of “genes”.
The idea that phenotypic variability had a clear cut
and mostly genetic explanation continued as the DNA centric
view of “what is a gene” emerged in the 1950s.
The shift in the definition of a gene also appears to
have contributed to the idea that variability in DNA
sequences would be the major driver of phenotypic
variability. In
this context, a frequently overlook concept is that
estimates of heritability are also dependent on relatively
stable environmental and cultural conditions.
For example heritability estimates for body mass
index (BMI, a measurement linked to body composition and
used in the study of obesity) are dependent on both the
socio economic status of the population being studied and
also any recent changes in the socio economic status of the
population being studied.
Likewise in Japan heritability estimates for height
since World War II are confounded by large generational
increases in height due to improved nutrition in the absence
of changes in DNA sequence.
For many human phenotypes including the prevalence of
many non-communicable diseases, migration studies show that
environment, behavior and cultural factors play a major role
in human phenotypic variation in the absence of DNA sequence
differences.
Observations such as these highlight the limitations of the
DNA centric view of human phenotypic variation.
They emphasize the idea that complex multidirectional
interactions between the environment, behavior,
physiological regulation and adaptation, and the genome
explain human phenotypic variation.
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| The MUSIC of Life: Biology Beyond the Genome ©Denis Noble |
