Final answer:
Heritability estimates might change over time due to environmental factors and genetic drift, as well as measurement error and sample size, which can affect the accuracy and representation of genetic variability in a population.
Step-by-step explanation:
Other than genetic mediation, there are multiple reasons why heritability estimates may change over time. One major influence is environmental factors, which can cause phenotypic variation independent of genetic differences. For example, exposure to the sun can lead to darker skin in individuals irrespective of their genetic makeup. Likewise, for some species, environmental conditions can dictate sex determination—a biological aspect usually governed by genetic factors. Genetic drift is another reason why heritability estimates can vary. This is due to chance events that result in certain individuals having more offspring than others, not necessarily because of advantageous traits, but often by mere luck, like being in the right place at the right time.
Additionally, measurement error in estimating heritability can lead to changes over time. Scientific measurements are never perfectly accurate, so variability in data collection or analytical methods might result in different heritability estimates. Sample size can also affect heritability estimates, as smaller populations may provide less accurate representations of genetic variability and could be more susceptible to random changes in allele frequencies.