true preferences, including those for child
health. This is an important area for further
exploration because it implies that seem-
ingly paternalistic policies, or expenditures
that change outcomes relative to what would
be chosen independently, may help people
to arrive at outcomes that they would them-
selves choose in the absence of scarcity.
Banerjee and Duflo (
) have recently
made the case for improving well-being by
reducing the number of decisions that people
have to make. They argue that in the United
States, people do not have to decide whether
to chlorinate their drinking water—it comes
that way; similarly, many employers enroll
people into retirement plans by default, less-
ening the need to actively make a choice to
save. In developing countries, on these topics
as well as others, people must make choices,
decisions, and trade-offs. The evidence from
. provides another argument for
why having so many choices can result in bad
outcomes; scarcity makes quality decision-
making difficult. Under such circumstances,
defaults and guide rails, such as default
option retirement plans, make quality deci-
sion-making easier and can have big payoffs
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Transforming Traditional Agriculture
Univ. Press, New Haven, London, 1964).
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4. E. Duflo, in
, A. Banerjee, R. Bena-
bou, D. Mookherjee, Eds. (Oxford Univ. Press, Oxford/
New York, 2006), chap. 24.
5. A. K. Shah
338, 682 (2012).
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Bank and Oxford University Press, Washington, DC,
7. E. Miguel, M. Kremer,
72, 159 (2004).
8. A. V. Banerjee, E. Duflo, R. Glennerster, D. Kothari,
340, c2220 (2010).
9. J. Cohen, P. Dupas,
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125, 1 (2010).
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Q. J. Econ.
126, 145 (2011).
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Annual Review of
2, 237 (2010).
12. M. Kremer, E. Miguel,
Q. J. Econ.
122, 1007 (2007).
13. P. Dupas,
3, 1 (2011).
14. H. Holla, M. Kremer, in
What Works in Development?
Thinking Big and Thinking Small
, J. Cohen, W. Easterly,
Eds. (Brookings Institution Press, Washington, DC, 2009),
15. A. Banerjee, E. Duflo,
Poor Economics: A Radical
Rethinking of the Way to Fight Global Poverty
Affairs, New York, 2011).
Getting to the Root of Aging
and James W. Vaupel
2, 3, 4
Why do patterns of aging differ widely across
the tree of life?
As people live longer, the question arises of how malleable aging is and whether it can be slowed or
postponed. The classic evolutionary theo-
ries of aging (
) provide the theoretical
framework that has guided aging research
for 60 years. Are the theories consistent
with recent evidence?
At the heart of the theories lies the obser-
vation that the old count less than the young:
Unfavorable traits are weeded out by evo-
lution more slowly at higher ages (
that are beneficial early in life are selected
for despite late life costs (
); and resources
are used to enhance reproduction at younger
ages instead of maintaining the body at ages
that do not matter much for evolution (
decline in the force of selection with age is
viewed as the fundamental cause of aging
). It is why, starting at reproductive matu-
rity, senescence—increases in susceptibility
to death and decreases in fertility—should be
inevitable in all multicellular species capable
of repeated breeding (
). Yet, this is not the
case. Increasing, constant, and decreasing
mortality (and fertility) patterns (see the fig-
ure) are three generic variants that compose
the rich diversity of life trajectories observed
in nature. For vertebrates, reproductive tra-
sus maintenance versus repro-
duction versus escaping preda-
tors and pathogens. The scar-
city of resources available for
competing needs requires that
an organism “makes difficult
choices” at every moment of life.
For instance, more energy dedi-
cated to growth at one moment
may reduce reproductive output
but improve chances of survival
to the next breeding opportunity,
when conditions might be bet-
ter and reproductive potential
(because of growth) higher (
Current theory of aging acknowl-
edges the necessity of such
) but neglects
their fundamental importance.
Because the declining force of
selection with age dominates
evolutionary thinking about
aging, classic theory focuses on
life-history choices that specifi-
cally confer early-life advantages at the cost
of late-life losses.
By widening horizons to consider not only
early- versus late-life compromises but all
the difficult choices an organism must make
in allocating limited resources to competing
needs over its life span, it is possible to gain
insights into the diverse demographic patterns
observed in nature (
). Even the effects
of purely deleterious mutations that act only
CREDIT: Y. HAMMOND/
Aging patterns. The illustration is a schematic view of how species
age in radically different ways. The life courses of humans and of
many mammals and birds, at least at the oldest ages, are gener-
ally marked by rising mortality. For the tortoise
) and many other reptiles, amphibians, fish, and plants, mortal-
ity decreases throughout adult life. For the freshwater polyp
) and various other species across the tree of life, daily
survival is more or less constant with age.
1Max Planck Research Group for Modeling the Evolution of
Aging, Rostock, Germany. 2Max Planck Institute for Demo-
graphic Research, Rostock, Germany. 3University of South-
ern Denmark, Odense, Denmark. 4Duke University, Dur-
ham, NC 27705, USA. E-mail: firstname.lastname@example.org
jectories are commonly hump-shaped, and
death rates may start rising much later than
reproductive maturity (
). Thus, a new view
on the fundamental causes of aging is needed
to explain the clash of theory and data.
Allocation theory, which seeks to explain
how resource limitations determine life-his-
tory patterns, provides a possible, promising
). Nature strikes compromises
in allocating limited resources to growth ver-
in this issue
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