Between Zeus and the Salmon The Biodemography of Longevity (1997) / Chapter Skim
Currently Skimming:
8 Population Biology of the Elderly
8 Population Biology of the Elderly
Pages 127-160
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 127... ...
For example, it does not consider circumstances in which only older adults, particularly females, overwinter and regenerate the population in the spring (Izquierdo, 1991) , in which the elderly provide infant care, or in which the older matriarchs or patriarchs provide critical leadership and cohesion.
|
From page 128... ...
Just as certain morphological traits in animals, such as antler type, leg length, wing shape, visual acuity, gut length, and ear design, have been successfully related to the ecology and life histories of different animal species, we expect longevity and mortality patterns to be interpretable in the same context. We believe that this approach will provide insight into questions such as: What aspects of natural history favor the evolution of greater longevity?
|
From page 129... ...
Life-Course Premises Many of the premises outlined by Riley (1979) for the life course and demography of older humans are general and thus relevant for understanding the life course, population dynamics, and aging of populations for any species.
|
From page 130... ...
First, long life prolongs opportunity to accumulate social and biological experiences. For example, long-lived individuals in social species may possess unique knowledge, such as the location of water during a drought or how to manufacture and use tools.
|
From page 131... ...
Diamond (1996) supports the occurrence of altruistic postreproductive females by stating that aging human females can, evidently, "do more to increase the number of people bearing her genes by devoting herself to her existing children, her potential grandchildren, and her other relatives than by producing yet another child." An example of altruism in a nonsocial species is given by Blest (1963~.
|
From page 132... ...
lists several "special properties" of dominance order that have important bearing on understanding the role of the elderly in social species. First, "the peace of strong leadership" refers to how dominant animals of some primate societies, including those of gorillas, chimpanzees, macaques, spider monkeys, and squirrel monkeys, use their power to terminate fighting among subordinates.
|
From page 133... ...
Information that can only be transmitted through learning includes home range, migratory pathways, location of food sources, tool construction and use, acceptability of food items, parental-care skills, and social relationships, such as pair bonding and alliances (Bonner, 1980~. THE ELDERLY IN NATURE: SELECTED CASE STUDIES Although there are few papers published on the elderly in nature, the biological literature contains a surprising amount of information on nonhuman elderly that has never been compiled and synthesized.
|
From page 134... ...
There are only two extant species, the African elephant and the Asian elephant, although there are a number of subspecies within each group (Estes, 1991~. The African forest elephant lives in the West African rain forest, whereas the savanna race inhabits lowland forests, low-lying swamps, flood plains, and woodland.
|
From page 135... ...
Juvenile Male Musth Bull pop Juvenile Female Matriarch Family FIGURE 8-2 The social organization of elephants includes a central family core consisting of the matriarch, other adult females, sexually mature and immature female offspring, and sexually immature juvenile males. The sexually mature juvenile males roam in isolated bachelor groups.
|
From page 136... ...
Therefore, older females tend to be the largest of their sex in the herd and, because elephants' social organization is matriarchal, the oldest females are usually the leaders (DiSilvestro, 1991; Redmond, 1991~. Despite disease and deterioration, aging females still have an important role in elephant society, and the movements of the herd are adaptable to an aging animal (Freeman, 1980~.
|
From page 137... ...
However, they were in their prime, although solitary as almost all adult males are, and in search of estrous females from many different herds (Poole and Moss, 1981; DiSilvestro, 1991~. The third major role of elderly elephants involves essentially the collective knowledge of the matriarchs.
|
From page 138... ...
summarizes the six main types of social organizations in primates that include: solitary territorial animals, monogamous pairs, matrilines, one-male territorial troops, multi-male societies, and one-male harems. First, solitary territorial animals, such as the pottos, inherit their home ranges from their mothers.
|
From page 139... ...
The life spans of most nonhuman primates have been estimated conservatively, in that the recorded age represents the time in captivity. Thus the ages of animals captured in the wild are underestimated by their age at entry into captivity; the ages of those still living are underestimated by the time they will continue to live.
|
From page 140... ...
As a consequence little attention has been given to old animals in the vast literature on primate behavior." The social rank of macaque females increases with age. For example, a daughter of a high-ranked female may adopt a home range overlapping her mother's range.
|
From page 141... ...
She referred to these as the "altruists." The concept of inclusive fitness offers an explanation for a ranking system that favors youthful females of high reproductive value combined with a defense system in which old females take great risks (Hamilton, 1964~. The rise and fall by age in the dominance hierarchy of three adult male chimpanzees from the long-term study by Goodall (1986)
|
From page 142... ...
In contrast, Jomeo was apparently not motivated to attain high social status despite his apparent physical capabilities. Cetaceans Whales and Dolphins Ecological Background Cetacea consists of two extant suborders Mysteceti, baleen whales, and Odontoceti, toothed whales (Carroll, 1988~.
|
From page 143... ...
Other behavioral differences between the suborders, including migration, foraging, communication, mating, and offspring care, can be seen as artifacts of their social organizations. Therefore, analysis of the dichotomous life histories of baleen and toothed whales may give insight into why they live as long (or as briefly)
|
From page 144... ...
Baleen whales reach a length and age that is almost twice that of toothed whales. The ratio of longevity to length clearly increases from baleen whales to toothed whales and then increases dramatically in dolphins (Table 8-3~.
|
From page 145... ...
a Baleen whales Balaenoptera acutorostrata Minke whale 47 28 1.7 Balaenoptera borealis Sei whale 74 47 1.6 Balaenoptera musculus Blue whale 110 67 1.7 Balaenoptera physalus Fin whale 114 45 2.6 Eschrichtius robustus Gray whale 70 46 1.5 Megaptera novaeangliae Humpback whale 77 46 1.7 Toothed whales Globicephala macrorhynchus Pilot whale 49.5 17 2.9 Orcinus orca Killer whale 50 24 2.1 Physeter catadon Sperm whale 77 44 1.8 Dolphins Stenella coeruleoalba Striped dolphin 34 9 3.8 Tursiops truncates Bottlenosed dolphin 35 9.8 3.6 aThis ratio was calculated by dividing longevity by length. Note: For species in which male and female data were supplied, the average was used.
|
From page 146... ...
Also, in pilot whales, females have an exceptionally long postreproductive period, ceasing ovulation at about 40 years, although they often live until age 63. In Japanese fisheries, 25 percent of females captured are postreproductive and 25 percent of the postreproductive females are lactating.
|
From page 147... ...
Evolution of Eusociality in Wasps Wasps are in the insect order Hymenoptera, which is thought to have evolved about 200 million years ago (Edwards, 1980~. This order contains a wide variety of species including the sawflies, parasitic hymenopterans, and most extant social insect species, including social wasps, ants, and bees.
|
From page 148... ...
Vertical bands or blocks represent length of association between parent and individual offspring; for example, stage I shows short duration of association between a solitary parasitoid wasp and its offspring. The parasitoid lays eggs in a sequence of hosts but provides no parental care, thus "abandoning" each offspring directly after oviposition.
|
From page 149... ...
Here the degree of parental care strongly increases the bond between adult and offspring. The assumption is that progressive provisioning arose from delayed provisioning (Evans, 1966~.
|
From page 150... ...
Phase IV Generation Overlap/Primitive Eusociality The female's life is prolonged and overlaps that of the progeny that remain with her in the nest to form an extended family. Females at this phase lay eggs into an empty cell, a trait thought important in permitting evolution of the extended brood care of social wasps (Evans, 1958; Carpenter, 1991~.
|
From page 151... ...
However, in more advanced groups, when queen longevity is several fold greater than workers, the worker life span is probably determined by needs of colony defense, predictability of food resources, and colony-maintenance requirements. TABLE 8-4 Maximum Size of Social Insect Colonies Given Different Worker Life Expectancies and Queen Daily Egg Production Queen Daily Egg Production Life Expectation 100 1000 10,000 100,000 20 days 2,000 20,000 200,000 2,000,000 50 days 5,000 50,000 500,000 5,000,000 100 days 10,000 100,000 1,000,000 10,000,000 200 days 20,000 200,000 2,000,000 20,000,000 SOURCE: Carey (1993; tables 5-12)
|
From page 152... ...
. It is important to recognize differences in evolutionary scales because the macroevolutionary scale provides context for broad differences in life spans, which may shed light on more subtle, microevolutionary differences.
|
From page 153... ...
This value is consistent with predictions of life spans based on correlations between longevity, brain weight, and adult size (Hayflick,1994~. Our approach combines biological and demographic logic with perspectives on the life histories of other species.
|
From page 154... ...
First, perspectives on the natural history of the elderly will provide a broader and deeper biological foundation for life-course analysis in demography, including the integration of concepts in demographic sociology (Riley and Riley, 1986) , those in sociobiology (Wilson, 1975)
|
From page 155... ...
Buss, I.O., and N.R. Smith 1966 Observations on reproduction and breeding behavior of the African elephant.
|
From page 156... ...
Douglas-Hamilton, I 1987 African elephants: population trends and their causes.
|
From page 157... ...
1973 Population dynamics of the African elephant (Loxodonta africana)
|
From page 158... ...
Wursig, eds., The Hawaiian Spinner Dolphin. Berkeley, CA: University of California Press.
|
From page 159... ...
1994 Sex differences in the behavior of African elephants.
|
From page 160... ...
154:235-248. 1971 The Natural History of the African Elephant.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.