E. Le Bourg

Reproductive life of french-canadians in the 17–18th centuries: A search for a trade-off between early fecundity and longevity

One of the predictions derived from Williams (1957) evolutionary theory of senescence is the existence of a trade-off between early fecundity and longevity. The population register of the French immigrants to Québec in the 17th century and of the first Canadians in the 17th and 18th centuries was used to detect such a trade-off in a noncontraceptive human population living at a time when longevity had not been prolonged by medical care and was not artificially shortened by wars, epidemics, or other external causes. No evidence for such a trade-off could be detected in these populations which had not yet reached the demographic transition phase (i.e., the historical period when longevity began to be extended and the progeny began to be reduced). Results are discussed in connection with the various studies aiming to test the Williams theory.

Hypergravity and aging in Drosophila melanogaster

The proboscis extension response threshold to sucrose has been measured in young, middle-aged and old male Drosophila melanogaster flies living at a gravity level of 1, 3.02 or 5.02 g until the experiment. The threshold increased with age and no effect of gravity level was observed at any age. These data are at variance with those of previously studied behavioral traits which showed that flies living in hypergravity seemed to age faster than 1-g ones.

Spontaneous locomotor activity and life span: a test of the rate of living theory in Drosophila melanogaster

The spontaneous locomotor activity and life span of approximately 600 individuals of both sexes and of three widely different genotypes of Drosophila melanogaster have been measured. Neither at the individual nor at the populational level could a significant correlation between spontaneous locomotor activity and life span be found. The results are discussed in relation with Pearls [The rate of living, London University Press, London 1928] rate of living theory. That theory has been tested in relation with environmental temperature, oxygen consumption and activity. It is shown that the theory has received no definite confirmation until now.

Hypergravity and Ageing in Drosophila melanogaster

Longevity of Drosophila melanogaster flies was observed at various gravity levels in three different breeding conditions of decreasing quality. A slight longevity decrease was obser

Decline in photopositive tendencies with age inDrosophila melanogaster (Diptera: Drosophilidae)

Phototaxis was measured in young, middle-aged, and oldDrosophila melanogaster flies of both sexes. The apparatus allowed us to measure the tendency to go toward light, independently of the time needed to do so; under such conditions, phototaxis is dissociated from locomotor activity. The percentage of photopositive flies decreased slightly with age (93.96, 80.17, and 78.97%, respectively, in young, middle-aged, and old flies). Results are discussed in connection with previous data for which the tendency to go toward light and the time to do so were not dissociated.

Evolutionary theories of aging : Handle with care

Background: Evolutionary theories are considered by a growing number of gerontologists as providing a basis to understand why aging occurs. Objective: In such conBackground: Evolutionary theories are considered by a growing number of gerontologists as providing a basis to understand why aging occurs. Objective: In such conditions, a risk could exist to favor evolutionary explanations rather than nonevolutionary ones, even when both equally fit the data. Methods: A paper recently published on longevity in ants is analyzed, and a study of fertility and longevity in human beings is done to illustrate this risk. Results: In the two cases, evolutionary and concurrent hypotheses may apply to the same data. Conclusions: When both kinds of explanations may be applied, the way to solve the problem is not to favor one explanation by relying on a priori preferences, particularly if the favored hypothesis is still controversial.

Aging and Habituation of the Tarsal Response in Drosophila melanogaster

The measure of the waning of an unconditioned response, viz. the extension of the proboscis in response to repetitive tarsal stimulations by sucrose, has been conducted in young and old Droso

Evolutionary theories of aging. 2. The need not to close the debate.

Background: Keller and Genoud [Gerontology 1999;45: 336–338] consider that a previous article of Le Bourg [Gerontology 1998;44:345–348] is an inappropriate criticism of evolutionary theories of aging and offer a refutation of this article. Objective: We answer that the article was not devoted to the criticism of evolutionary theories of aging but, rather, to the sometimes fast tackling of these theories on what is observed in the wild. Furthermore, we answer to the specific points contained in the Keller and Genoud’s article (longevity of ants, reproduction in mammals, and the case of the human species). Conclusion: The debate about evolutionary theories of aging is not closed: it would be an error to try to do it before a consensus has been reached.

Selection for increased longevity in Drosophila melanogaster: reflections on new data.

In recent papers, new data were presented on the late-age reproduction experiment initiated by Luckinbill and Clare in 1981: when early- and late-reproduced lines were compared simultaneously 10 years after the end of the original experiment, differences in the mean life span are observed between the lines. Yet the conditions in which these measurements were done are highly questionable. More fundamentally, using these data, the analysis of the selection process is impossible and conclusions about the determinism of life span are debatable.

Research on aging in France

This article gives some information on the French research on aging using a survey of the European Commission on research on aging in Europe and the answers to a questionnaire sent to the laboratories involved in aging research. France is involved in the European effort, but to a lesser degree than could be expected from its population size, and this picture has not changed during the last decade. The answers to the questionnaire allow us to know the opinion of colleagues on the strengths and weaknesses of French research: the lack of money and institutional recognition seem to hinder the development of experimental gerontology in France.