Many epigenetic changes are heritable to a degree. Many personality traits have a genetic component and are highly heritable. Historically, some phenomena not necessarily heritable have also been described as epigenetic. Relatively large body mass may be a heritable trait. Such techniques take advantage of the stable and heritable RNAi phenotype in plant stocks. Therefore, the chronotype is genetically heritable. As mentioned above, some define epigenetics as heritable. Quantitative studies of heritable traits throw light on the question. Most of these are single-gene defects, usually heritable. Evolution is change in the heritable characteristics of biological populations over successive generations. The second was to argue that the acquired traits were heritable. This method of selection will only be effective for highly heritable traits. This process differs from somatic cell engineering, which does not result in heritable changes. These magnitudes are considered small because they do not explain much of the heritable variation. It found that telomere length was 70% heritable.