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if humans were
BUILT TO LAST
Curved neck
Forward-tilting
upper torso
Extra padding
around joints
Reversed
knee joint
PERSON DESIGNED FOR A HEALTHY OLD AGE might possess
the features highlighted here, along with countless other
external and internal adjustments.
Rewired eyes
Bigger ears
Shorter limbs
and stature
By S. Jay Olshansky, Bruce A. Carnes and Robert N. Butler
Illustrations by Patricia J. Wynne
94
FAST-FORWARD
Bulging disks, fragile bones, fractured
hips, torn ligaments, varicose veins,
cataracts, hearing loss, hernias and
hemorrhoids: the list of bodily mal-
functions that plague us as we age is
long and all too familiar. Why do we
fall apart just as we reach what should
be the prime of life?
The living machines we call our bodies deteriorate
because they were not designed for extended operation
and because we now push them to function long past
their warranty period. The
human body is artistically
beautiful and worthy of all
the wonder and amazement it
evokes. But from an engi-
neer’s perspective, it is a com-
plex network of bones, mus-
cles, tendons, valves and joints
that are directly analogous to
the fallible pulleys, pumps,
levers and hinges in machines.
As we plunge further into our
postreproductive years, our
joints and other anatomical
features that serve us well or
cause no problems at younger
ages reveal their imperfec-
tions. They wear out or oth-
erwise contribute to the
health problems that become
common in the later years.
In evolutionary terms, we
harbor flaws because natur-
al selection, the force that molds our genetically con-
trolled traits, does not aim for perfection or endless
good health. If a body plan allows individuals to sur-
vive long enough to reproduce (and, in humans and
various other organisms, to raise their young), then
that plan will be selected. That is, individuals robust
enough to reproduce will pass their genes—and there-
fore their body design—to the next generation. Designs
that seriously hamper survival in youth will be weed-
ed out (selected against) because most affected indi-
viduals will die before having a chance to produce off-
spring. More important, anatomical and physiological
quirks that become disabling only after someone has re-
produced will spread. For example, if a body plan leads
to total collapse at age 50 but does not interfere with
earlier reproduction, the arrangement will get passed
along despite the harmful consequences late in life.
Had we been crafted for extended operation, we
would have fewer flaws capable of making us miserable
in our later days. Evolution does not work that way,
however. Instead it cobbles together new features by tin-
kering with existing ones in a way that would have
made Rube Goldberg proud.
The upright posture of humans is a case in point. It
was adapted from a body plan that had mammals walk-
ing on all fours. This tinkering undoubtedly aided our
early hominid ancestors: standing on our own two feet
is thought to have promoted
everything from food gather-
ing and tool use to enhanced
intelligence. Our backbone
has since adapted somewhat
to the awkward change: the
lower vertebrae have grown
bigger to cope with the in-
creased vertical pressure,
and our spine has curved a
bit to keep us from toppling
over. Yet these fixes do not
ward off an array of prob-
lems that arise from our bi-
pedal stance.
What If?
RECENTLY
the three of us
began pondering what the
human body would look
like had it been constructed
specifically for a healthy long
life. The anatomical revi-
sions depicted on the following pages are fanciful and
incomplete. Nevertheless, we present them to draw at-
tention to a serious point. Aging is frequently described
as a disease that can be reversed or eliminated. Indeed,
many purveyors of youth-in-a-bottle would have us be-
lieve that the medical problems associated with aging
are our own fault, arising primarily from our decadent
lifestyles. Certainly any fool can shorten his or her life.
But it is grossly unfair to blame people for the health
consequences of inheriting a body that lacks perfect
maintenance and repair systems and was not built for
extended use or perpetual health. Our bodies would still
wear out over time even if some mythical, ideal lifestyle
could be identified and adopted.
This reality means that aging and many of its accom-
www.sciam.com SCIENTIFIC AMERICAN 95
We would look
a lot different
if evolution
had designed
the human body
to function
smoothly for a
century or more
Continued on page 99
FLAWS
JOINTS THAT WEAR
As joints are used repetitively
through the years, their lubricants
can grow thin, causing the bones
to grind against each other.
The resulting pain may be
exacerbated by osteoarthritis
and other inflammatory disorders
BONES THAT LOSE MINERALS AFTER AGE 30
Demineralization makes bones susceptible to
fractures and, in extreme cases, can cause
osteoporosis (severe bone degeneration),
curvature of the spine and “dowager’s hump”
FALLIBLE SPINAL DISKS
Years of pressure on the spongy disks that
separate the vertebrae can cause them to slip,
rupture or bulge; then they, or the
vertebrae themselves, can press
painfully on nerves
LEG VEINS PRONE TO VARICOSITY
Veins in the legs become enlarged
and twisted when small valves that should
snap shut between heartbeats (to keep blood
moving up toward the heart)
malfunction, causing blood to pool.
Severe varicosities can lead
to swelling and pain
and, on rare occasions,
to life-threatening blood clots
MUSCLES THAT LOSE MASS AND TONE
Such atrophy can impede all activities,
including walking. In the abdomen, hernias
can arise as the intestines (always pulled by
gravity) protrude through weak spots
in the abdominal wall. Flaccid abdominal
muscles also contribute to lower-back pain
A NUMBER OF the debilitating and even
some of the fatal disorders of aging stem in
part from bipedal locomotion and an
upright posture—ironically, the same
features that have enabled the human
species to flourish. Every step we take
places extraordinary pressure on our feet,
ankles, knees and back—structures that
support the weight of the whole body
above them. Over the course of just a
single day, disks in the lower back are
subjected to pressures equivalent to
several tons per square inch. Over a
lifetime, all this pressure takes its toll, as
does repetitive use of our joints and the
RELATIVELY SHORT
RIB CAGE
Current cage
does not fully
enclose and protect
most internal organs
Pooled blood
Malfunctioning
check valve
Normal direction
of blood flow
96 SCIENTIFIC AMERICAN Updated from the March 2001 issue
WALK THIS WAY
EXTRA MUSCLES AND FAT
Would add weight on the bones, which would help
counter the effects of demineralization; they
would also cushion bones against
breakage during falls
SHORTER STATURE
Would provide a lower
center of gravity, perhaps
preventing the falls
that often fracture
demineralized bones
Smooth-
flowing
blood
FORWARD-TILTING UPPER TORSO
Would relieve pressure on vertebrae, thereby lessening the risk
of ruptured or slipped disks, which contribute, along with
weakening abdominal muscles, to lower-back pain
CURVED NECK WITH ENLARGED VERTEBRAE
Would counterbalance the tilted torso and enable the
head to stay up and face forward
constant tugging of gravity on our tissues.
Although gravity tends to bring us
down in the end, we do possess some
features that combat its ever present pull.
For instance, an intricate network of
tendons helps to tether our organs to the
spine, keeping them from slumping down
and crushing one another.
But these anatomical fixes—like the
body in general—were never meant to work
forever. Had longevity and persistent good
health been the overarching aim of
evolution, arrangements such as those
depicted below might have become
commonplace.
KNEE ABLE TO BEND BACKWARD
Would make the bones less likely to grind
and deteriorate, especially if the knee never
locked in place. But the absence of a locking
mechanism would make it hard to stand for
very long, so further modifications
would be needed
THICKER BONES
Would protect
against breakage
during falls
LEG VEINS WITH MORE
CHECK VALVES
Would combat
the development
of varicose veins
Extra
valves
THICKER DISKS
Would resist destructive pressures
LARGER HAMSTRINGS
AND TENDONS
Would help support
the leg and hip
CAGE WITH
ADDED RIBS
Could help prevent hernias
and other problems by
holding organs in
place more effectively
www.sciam.com SCIENTIFIC AMERICAN 97
FIXES
98 SCIENTIFIC AMERICAN NEW LOOK AT HUMAN EVOLUTION
VARIOUS PARTS of the head and
neck become problematic with
disturbing regularity as people
age. Consider the eye: the human
version is an evolutionary marvel,
but its complexity provides many
opportunities for things to go
wrong over a long lifetime.
Our vision diminishes as the
protective fluid of the cornea
becomes less transparent over
time. The muscles that control the
opening of the iris and the
focusing of the lens atrophy and
lose responsiveness, and the lens
thickens and yellows, impairing
visual acuity and color
perception. Further, the retina—
responsible for transmitting
images to the brain—can detach
fairly easily from the back of the
eye, leading to blindness.
Many of those problems would
be difficult to design away, but
the squid eye suggests an
arrangement that could have
reduced the likelihood of retinal
detachment. A few anatomical
tweaks could also have preserved
hearing in the elderly.
Suboptimal design of the
upper respiratory and digestive
systems makes choking another
risk for older people. A simple
rearrangement would have fixed
that problem, albeit at the cost
of severe trade-offs.
WEAK LINK BETWEEN RETINA
AND BACK OF EYE
This frail connection exists in part
because the optic nerve, which carries
visual signals from the retina to the
brain, connects to the retina only from
the inside of the eye, not from the back
COMMON UPPER PASSAGEWAY FOR FOOD AND AIR
When food travels toward the esophagus, a
flaplike tab of cartilage (the epiglottis) closes off
the trachea, or windpipe. With age, a progressive
loss of muscle tone decreases the tightness of
the seal, raising the risk of inhaling food or drink
FLAWS
FIXES
ENLARGED, MOBILE OUTER EAR
Would collect sound with greater
efficiency, to compensate for
internal breakdowns
MORE PLENTIFUL AND
DURABLE HAIR CELLS
Would preserve hearing longer
OPTIC NERVE ATTACHED
TO BACK OF RETINA
Might stabilize the retina’s
connection to the back of
the eye, helping to prevent
retinal detachment
Unwanted flow of food
Safer flow of food
RAISED TRACHEA
Would help food and drink to bypass the windpipe more
effectively. This design would need refining, though,
because it would disrupt breathing through the mouth
and the ability to speak
Trachea
Trachea
Esophagus
Esophagus
Epiglottis
Optic
nerve
Retina
PLAN A HEAD
EAR WITH FRAGILE
TRANSMITTERS
Hair cells of the inner
ear, which relay
sound information to
the brain, become
damaged by exposure
to loud noises
Detached retina
panying disorders are neither unnatural nor avoidable. No sim-
ple interventions can make up for the countless imperfections
that permeate our anatomy and are revealed by the passage of
time. We are confident, however, that researchers in the vari-
ous biomedical sciences will be able to ease certain of the mal-
adies that result from our extended life spans. Investigators are
rapidly identifying (and discerning the function of) our myriad
genes, developing pharmaceuticals to control them, and learn-
ing how to harness and enhance the extraordinary repair capa-
bilities that already exist inside our bodies. These profound ad-
vances will eventually help compensate for many of the design
flaws contained within us all.
Health, Longevity
OUR RESEARCH
interest in redesigning the Homo sapiens
body is a reaction to the health and mortality consequences of
growing old. We focus on anatomical “oddities” and “design
flaws” not only because they would be familiar to most read-
ers, but because they represent a small sample of lethal and dis-
abling conditions that threaten the length and quality of life. It
is important to recognize that we live in a world in which hu-
man ingenuity has made it possible for an unprecedented num-
ber of people to grow old. Our redesign goal is thus to draw
attention to the health consequences associated with the aging
of individuals and populations.
One critical message we wish to convey is that people were
www.sciam.com SCIENTIFIC AMERICAN 99
AN EXPERIENCED PLUMBER
looking at the anatomy of
a man’s prostate might
suspect the work of
a young apprentice,
because the urethra, the
tube leading from the
bladder, passes straight
through the inside of the
gland. This configuration
may have as yet unknown
benefits, but it eventually
causes urinary problems in
many men, including weak
flow and a frequent need
to void.
Women also cope with
plumbing problems as they
age, particularly
incontinence. Both sexes
could have been spared
much discomfort if
evolution had made some
simple modifications
in anatomical design.
Wall muscle
Direction of
urine flow Sphincter
Ligament
Bladder
Bladder
Ureter
Enlarged
prostate
MALE PROSTATE
side view FEMALE BLADDER
front view
FIX
URETHRA HUGGING OUTSIDE OF PROSTATE
Would not be squeezed if the
prostate became enlarged
FLAW
URETHRA PRONE TO CONSTRICTION
The prostate becomes enlarged in one of every two
males at some point in life. As it grows, it squeezes
the urethra, potentially obstructing the flow of
urine. Total obstruction can be fatal
Repositioned
urethra
Ureter
from
kidney
CALL A PLUMBER
Direction of
urine flow
Urethra
FLAW
MUSCLES AND LIGAMENTS THAT WEAKEN WITH TIME
Particularly after multiple pregnancies,
the muscles of the pelvic floor and the bladder, and the
ligaments that support the bladder, can sag,
leading to incontinence
FIX
STRONGER SPHINCTER MUSCLES IN BLADDER
AND MORE DURABLE LIGAMENTS
Would increase control over bladder function
Larger
sphincter
Stronger
wall
muscle
Larger
ligament
Continued from page 95
not designed by evolution for extended survival, so it is not their
fault that they ultimately suffer age-related ailments. Most of
what goes wrong with us as we grow older is a product of op-
erating our living machines beyond their biological warranty
period. Although we have considerable control over the quali-
ty of our lives, we still don’t have much control over the length
of our lives.
Even the term “flaw” requires clarification. Living things,
and everything they make, eventually fail. The cause of failure
is a flaw only when the failure is premature. A race car that fails
beyond the end of the race has no engineering flaws. In the same
way, bodies that fail in the postreproductive span of life may
contain numerous design oddities, but they have no design flaws
as far as evolution goes. Aging, disease and death are natural
by-products of bodies that were optimized for reproduction.
There are countless other aspects of human biology that
would merit modification if health and longevity were nature’s
primary objective. For example, gerontologists theorize that
aging is caused, in part, by a combination of the molecular
damage that inevitably arises from operating the machinery of
life within cells and the imperfect mechanisms for molecular
surveillance, maintenance, and repair that permit damage to
accumulate over time. If this view of the aging process is cor-
rect, then modifying these molecular processes to lessen the
severity or accumulation of damage, or to enhance the main-
tenance and repair processes, should have a beneficial impact
on health and longevity. These wondrous modifications, how-
ever, would have little effect unless the common sense that is
needed to avoid destructive lifestyles becomes more wide-
spread among people.
Living things are exceedingly complex, and experience
teaches us that undesirable consequences invariably arise when-
ever humans have taken over the reins of evolution in order to
modify organisms (microbes, plants and animals) to suit their
purposes. The most worrisome trade-off for genetic manipula-
tion directed toward living longer would be an extension of
frailty and disability rather than an extension of youthful health
and vitality.
Though cobbled together by the blind eye of evolution, hu-
mans have proved to be a remarkably successful species. We
have outcompeted almost every organism that we have en-
countered, with the notable exception of microbes. We have
blanketed the earth and even walked on the moon. We are also
one of the only species that has figured out how to escape pre-
mature death and survive to old age.
At this point in history, we need to exploit our expanding
knowledge of evolution to enhance the quality of our lives as
we grow older, because the single-minded pursuit of life exten-
sion without considering health extension could be disastrous.
Our fanciful designs of anatomically “fixed” humans are
not intended as a realistic exercise in biomechanical engineer-
ing. Given what is known today about human aging, if the task
of designing a healthy long-lived human from scratch were giv-
en to a team comprising the father of evolution, Charles Dar-
win, the great painter Michelangelo, and the master engineer
and scientist Leonardo da Vinci, they most certainly would have
fashioned a living machine that differs from the one we now oc-
cupy. Indeed, anyone who tries his hand at redesign would
probably construct a human body that would look unlike the
ones we’ve created on these pages. Yet we invoke this approach
as an instructive way of communicating the important message
from evolutionary theory that, to a significant degree, the po-
tential length of our lives and, to a lesser degree, the duration of
health and vitality are genetic legacies from our ancient ances-
tors, who needed to mature quickly to produce children before
they were killed by the hostile forces of nature.
100 SCIENTIFIC AMERICAN NEW LOOK AT HUMAN EVOLUTION
On Growth and Form. D’Arcy Wentworth Thompson. Expanded edition,
1942. (Reprinted by Dover Publications, 1992.)
The Panda’s Thumb: More Reflections in Natural History. Reissue
edition. Stephen Jay Gould. W. W. Norton, 1992.
The Blind Watchmaker: Why the Evidence of Evolution Reveals a
Universe without Design. Reissue edition. Richard Dawkins. W. W.
Norton, 1996.
The Scars of Evolution: What Our Bodies Tell Us about Human Origins.
Reissue edition. Elaine Morgan. Oxford University Press, 1994.
Why We Get Sick: The New Science of Darwinian Medicine. Randolph M.
Nesse and George C. Williams. Vintage Books, 1996.
The Olshansky and Carnes Web site is www.thequestforimmortality.com
The International Longevity Center Web site is www.ilcusa.org
MORE TO EXPLORE
We need to EXPLOIT OUR KNOWLEDGE of
evolution to enhance our quality of life as we grow older.
S. JAY OLSHANSKY, BRUCE A. CARNES and ROBERT N. BUTLER all
have an enduring interest in the processes that underlie human
aging. Olshansky is professor in the School of Public Health at the
University of Illinois at Chicago. He and Carnes, both senior re-
search scientists at the National Opinion Research Center/Cen-
ter on Aging at the University of Chicago, collaborate on studies—
funded by the National Institute on Aging (NIA) and NASA—of the
biodemography of aging (examining the biological reasons for
age-related patterns of disease and death in populations). They
are co-authors of The Quest for Immortality: Science at the Fron-
tiers of Aging (W. W. Norton, 2001). Butler is president of the In-
ternational Longevity Center in New York City and was founding
director of the NIA.
THE AUTHORS
