Between Zeus and the Salmon The Biodemography of Longevity (1997) / Chapter Skim
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11 Intergenerational Relations and the Elderly
11 Intergenerational Relations and the Elderly
Pages 212-233
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From page 212... ...
Austad indicates that 24 percent of female short-finned pilot whales survive past the physiological reproductive age, at which point their remaining life expectancy is 14 years. In some killer whale populations, about 30 percent of females are postreproductive, and postreproductive life expectancy is over 25 years.
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From page 213... ...
, although often the sterility of the couple is due to sterility of the male rather than the female. Evidence for survival in high-mortality populations comes from a variety of sources that include skeletal data, contemporary preagricultural populations who retain traditional life styles, high-mortality agricultural populations, and extrapolation from agricultural populations using statistical methods to generate model life-table systems.
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From page 215... ...
concluded that the Mung had a life expectancy at birth of about 30 years in the past, although in recent years it appears to have been much higher. She also found that the Mung lit may be questioned whether these model life tables, based as they are on extrapolation from the experience of modern high-mortality agricultural populations, are appropriate for preagricultural populations.
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From page 216... ...
, indicating that in a stationary female population, 28 percent would be postreproductive.2 Further evidence is summarized by Wilmoth (1995) , who surveys a large number of estimated life tables for high-mortality populations and for each tabulates estimated life expectancy at birth and at age 50 (these are the only data he provides)
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From page 217... ...
Looking to the future, Table 11- 1 also shows data projected to the year 2065, at which point the life expectancy at birth is 90 years, 50 percent of the stationary female population would be postreproductive, and 28 percent would be at or above age 65. We can conclude that in our preagricultural past, postreproductive females probably made up a substantial proportion of the population.
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From page 218... ...
Causality might run from prosperity to coresidence of the grandparents, rather than the reverse, at least in human populations. Grandparents with a number of adult children might choose the most prosperous to live with, and grandparents might be sent away when food is inadequate to support them.
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From page 219... ...
This view contrasts starkly with one of the best-known theories of fertility for traditional human societies (Caldwell, 1976~. Caldwell's theory is based on the premise that in traditional societies, children transfer resources to their parents and are in other ways instrumentally useful to them: The key issue here, and, I will argue, the fundamental issue in demographic transition, is the direction and magnitude of intergenerational wealth flows or the net balance of the two flows one from parents to children and the other from children to parents over the period from when people become parents until they die....
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From page 220... ...
The thick arrows are most useful for comparing different kinds of transfer flows within the same population, such as child support, bequests, or a public sector pension system. il This diagrammatic approach provides a way to assess the overall direction of nter-age transfer flows in a population, thereby answering the first question about net direction of transfer flows in a population.
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From page 221... ...
They all point distinctly downward, indicating that the direction of transfer flows is, on net, from older to younger. This contradicts the statement from Caldwell quoted above, if his statement is taken to refer strictly to transfers of foods and other easily measured physical items.
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From page 222... ...
permit younger members of the population to be more productive, or they make tools for younger hunters (Hill and Hurtado, 1996:235-236~. For these reasons, some degree of upward-flowing physical transfers from adult children to elderly parents could be consistent with the demands of reproductive fitness.
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From page 223... ...
Such services make it very difficult to assess a broader version of Caldwell's theory, and clearly at times it is this broader version that Caldwell has in mind.3 So far I have discussed only preindustrial transfer flows. In the preindustrial societies for which I have presented data, the public sector was small, and its tax and transfer role was minimal.
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From page 224... ...
However, the net flows up to surviving elders are overwhelmed in value by the value of net flows downward from parents to children earlier in the life cycle, so the net direction of transfers flows overall is definitely downward, as shown earlier in Figure 11-2. There is an obvious reason why the elderly in the United States continue to make net transfers to their adult children, in contrast to most preindustrial societies so far examined (except for those studied by Kaplan, 1994~.
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From page 225... ...
. NOTES: The four arrows represent bequests to children at death of parent; interhousehold transfer flows between no-longer coresident parents and children; parental costs of higher education; and parental costs of child rearing, net of children's earnings as teenagers.
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From page 226... ...
Indeed, when the upward transfers through the public sector are combined with the downward transfers through the family shown in Figure 11-3, the net direction of transfer flows is still up
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From page 227... ...
argued that fertility is low in industrial societies because wealth flows have been reversed in these societies, with children now imposing substantial net costs on their parents rather than being the source of upward transfer flows. In fact, we have just seen that in the United States, net transfer flows are upward, not downward.
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From page 228... ...
Furthermore, a gene for reneging would convey lower reproductive fitness in this example, because it also would be transmitted to offspring, and reproductive fitness would return to the original baseline level, which is by hypothesis lower than that with the repayment gene. In this way, evolution could lead to life-cycle patterns of intergenerational transfers in which some parental investment in children is subsequently "repaid" by the child at a later life-cycle stage that is, patterns in which transfers in both directions occur between parents and children, at different ages.
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From page 229... ...
Indeed, the ownership of property is one of the major ways in which elderly parents have induced their children to transfer flows of resources upward to them, as in the example given above in which inter vivos transfer of the farm to a child carried a contractual obligation on the part of the child to provide food for the elderly parents. Because it appears from Austad (in this volume)
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From page 230... ...
· Widely available data would support the analysis of the effect on infant and child mortality of the presence of a grandparent in human agricultural households, if direction of causality can be established. · Although upward transfer flows may be altruistic in humans, it is also possible that because the elderly can increase the reproductive fitness of their adult children, their children could enhance their own reproductive fitness by transferring resources to their parents.
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From page 231... ...
I have argued that postreproductive females and older males were quite prevalent in preagncultural human populations and that they probably raised the reproductive fitness of their children through leadership, knowledge, and food transfers. It is unknown, however, whether the longevity of humans can, in fact, be explained by the usefulness of older humans.
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From page 232... ...
McDaniel, and C Grushka 1993 New model life tables for high-mortality populations.
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From page 233... ...
U.S. Social Security Administration 1992 Life Tables for the United States Social Security Area, 1990-2080.
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