What are the causes of human longevity?

Tracking down the causes of aging

How immutable is the process of aging? Can it be slowed down or postponed? With the so-called allocation theory, scientists from Rostock explain why aging processes in nature are flexible and depend on species-specific compromises.

In an article in Science Magazin, Dr. Annette Baudisch, head of the research group “Model development for the evolution of aging” at the Max Planck Institute for Demographic Research (MPIDR), and Prof. James W. Vaupel, MPIDR director and head of the work areas “Aging and Longevity” and “Evolutionary Demography “Represents what distinguishes their approach from classical, evolutionary-oriented approaches of age research.

The scientists compared the aging patterns of different species with each other and calculated whether there was a connection to their reproduction. "Aging shows up here as a balance between wear and repair processes," explains Baudisch. “It's a kind of cost-benefit calculation. What percentage is a species in reproduction, how much in survival or growth? "

Compromises between growth, maintenance and reproduction

The decline in selection pressure is commonly seen as a fundamental cause of aging. It is assumed that senescence is inevitable for all multicellular species, which begins at the time of reproductive ability and is associated with an increasing probability of death and reduced fertility. In the opinion of the Rostock scientists, however, this is not the case at all. “In fact, you can see rising, constant, and falling mortality and fertility patterns across species. These represent three general variants, which underlie the rich variety of possible life curves in nature, ”says Baudisch.

In the allocation theory borrowed from economics, she sees a promising perspective for describing how life-course patterns are formed from the limitations of resources. "In nature, when distributing limited resources, compromises are made between growth, conservation, reproduction and defense against predators and pathogens," explains Baudisch. "In the early stages of life, survival is usually more important than reproduction, although the chances of reproduction at a later point in time are often higher due to the greater growth then achieved."

For some living beings, for example, it might make sense to spend more energy on growth than on reproduction for a longer period of time. Age research, based on evolutionary theory, does admit that there is a need for such compromises, but ignores their fundamental importance.

Insights into diverse demographic patterns in nature

In order to broaden horizons in this regard, the scientists advocate analyzing as closely as possible all the complicated decisions that living beings are subjected to during their entire existence due to the pressure of competition. As a result, they expect insights into the various demographic patterns that can be observed in nature.

Little is known about the conditions that lead to the development of such opposing aging patterns. It is assumed, among other things, that power distribution plays a central role. In order to test such hypotheses, the scientists propose to examine more closely the different palette of options of species, which are composed of the possible combinations of survival and reproduction at all ages over the entire lifespan.

Findings that shed light on the relationship between growth, maintenance, fertility and mortality in aging patterns are not yet available based on studies in the laboratory, in the zoo or in the wild. However, new statistical methods and new software could fill existing gaps in the observation data. “These mathematical models are very general,” says Baudisch, “but they help to understand general mechanisms.” They could also help to better understand the aging process in humans, which for modern humans differs significantly from other species.

 

Miriam Buchmann-Alisch

 

Additional information:

Annette Baudisch and James W. Vaupel: "Getting o the Roots of Aging - Why do patterns of aging differ widely across the tree of life?", Science, November 2, 2012, Vol. 338 no. 6107 pp. 618-619DOI: 10.1126 / science.1226467

Photo front page: © William Warby, Turtle's Head, Flickr