JOURNAL OF ANTI-AGING MEDICINE Volume 4, Number 2, 2001 Mary Ann Liebert, Inc.

When Does Human Longevity Start?:
Demarcation of the Boundaries for Human Longevity

NATALIA S. GAVRILOVA and LEONID A. GAVRILOV

ABSTRACT

The scientific debates on the future of human life span and its possible biological limits revealed a great need for direct identification of longevity boundaries, if they really exist. The key question posed in this study is as follows: how can we possibly determine the age when human longevity starts? To address this problem, we studied the familial transmission of human life span from parents to daughters, since daughters did not have a high incidence of violent causes of death due to military service and are particularly responsive to parental life span. We found that the familial transmission of human life span from mother to daughter is essentially nonlinear with virtually no daughter-mother life span resemblance for shorterlived mothers (died before age 85) and very high familial resemblance (additive heritability) for longer-lived mothers.

This indicates that maternal age of 85 years could be considered as a demarcation point (lower boundary) for female longevity. Women who live above this age are fundamentally (presumably genetically) different from other women in the sense that their daughters live significantly longer. Thus, the age of 85 years could be considered as a threshold age when women mortality becomes much more selective.

A similar study of familial transmission of human life span from father to daughter revealed a demarcation point at 75 years, suggesting that this age might represent a lower boundary for male longevity.

These results are also consistent with predictions of the evolutionary theory of aging and mutation accumulation theory in particular, namely that the additive genetic variance for human life span should increase with parental longevity. In other words, human mortality should become more selective at advanced ages, and this prediction is confirmed in the present study.

INTRODUCTION

THE SCIENTIFIC DEBATES on the future of human life span and its possible biological limits revealed a great need for direct identification of longevity boundaries, if they really exist. The key question posed in this study is as follows: how can we possibly determine the age when human longevity starts? To address this problem, we studied the familial transmission of human life span from parents to daughters, since daughters did not have a high incidence of violent causes of death due to military service and are known to be particularly responsive to parental life span.

If human life span is inherited just as any other polygenic quantitative trait, then the monotonic linear dependence between offspring life span and parental life span is expected. In this case, no evidence for any boundaries of human longevity could be detected.

On the other hand, if a special age corresponding to longevity Center on Aging, NORC/University of Chicago, Chicago, Illinois. boundary does really exist, this could be detected as a breaking point in the offspring-parent life span dependence. In this study, we found evidence for breaking points at about 85 years for females (mothers) and at about 75 years for males (fathers) that allowed us to identify the lower boundaries for human longevity in males and females.

Main data source

In this study, we collected, computerized, and analyzed detailed genealogical records on life span of 5,779 adult daughters (301 years) and their parents, using particularly reliable and complete data on European royal and noble families for extinct birth cohorts (born 1800–1880).

RESULTS AND DISCUSSION

the dependence between daughters’ life span and maternal life span looks like consisting of two pieces. Daughters born to shorter-lived mothers (died before 85 years) seem to demonstrate very weak resemblance with maternal life span. It does not really matter for daughters’ life span whether their mothers lived 40 years only, or as long as 80 years—the corresponding increase in daughters’ life span is below 2 years for 40 years of additional maternal life span.

On the other hand, daughters born to longerlived mothers (died after 85 years) demonstrate remarkably steep increase of their life span with maternal life span . These graphical observations are confirmed by statistical analysis presented at Table 1. The familial transmission of human life span from mother to daughter is essentially nonlinear (consisting of two different lines) with virtually no familial resemblance for shorter-lived mothers (died before 85 years).

the age of 85 years could be considered as a threshold age when female mortality becomes much more selective, and this age threshold in death selectivity should be taken into account in biogerontological studies of human longevity as well as in forecasting human life expectancy for women. The dependence between daughters’ life span and paternal life span looks like consisting of two lines, but the breaking point between these two lines is observed at earlier parental age—about 75 years. Daughters born to shorter-lived fathers (died before 75 years) do not inherit paternal life span.

A study of familial transmission of human life span from father to daughter suggests a demarcation point at 75 years, indicating that this age may represent a lower boundary for male longevity. The familial transmission of human life span from father to daughter is also nonlinear (consisting of two different lines), with virtually no resemblance before paternal life span of 75 years. The obtained results are consistent with the predictions of the evolutionary theory of aging and mutation accumulation theory in particular, namely that the additive genetic variance for human life span should increase with parental longevity.

The results obtained in this study also explain the existing longevity paradox: although the heritability estimates for life span were reported to be rather low, it is well known that cases of extreme longevity have a strong familial association. This paradox is explained by our finding that heritability of human life span is low only when studied in the whole range of parental life span (because most of the parents did not live long lives in historical populations studied so far), but is quite high when estimated specifically for longerlived parents. The results of this pilot exploratory study justifies the need for further full-scale research project on trajectories of parent–offspring transmission of human longevity.

Further studies on larger samples with additional consideration of many other explanatory and confounding variables (such as parental ages at person’s birth, etc.) are planned and may shed more light on the mechanisms of life span inheritance and the boundaries for human longevity.