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From Part One
Human Pachyderms
Snakes don’t get wrinkles. Instead, they shed their old skins and sport
shiny new ones in their place. Birds don’t get wrinkles. Worn feathers
are replaced when the birds molt. Mammals, in contrast, keep the skins
in which they are born. While it is true that the outermost layer of
any mammal’s skin constantly sheds dead cells, our true skin (dermis)
remains with us all our lives. The need to be “comfortable in our own
skin” is something we mammals need to take seriously; we have no place
else to go.
Humans are (nearly) hairless mammals, and that is an important fact
when our skin and its wrinkles are being considered. For the first two
hundred million years of mammalian evolution, skin was rarely, if ever,
exposed to the powerful rays of the sun. Among the proven benefits of
being covered with fur, as nearly all mammals are, is that fur protects
delicate mammalian skin from damage by the ultraviolet rays in sunlight.
If you doubt that hair is nature’s own sunscreen, look closely at a
balding man. Notice how the wrinkled brow, which has been exposed to
the sun for decades, gives way to a scalp as smooth as a baby’s bottom.
Hairlessness, as most middle-aged men would agree, is not the natural
state for mammals. Indeed, most of our fellow “naked” mammals live in
environments that shelter them from the sun. Hairless burrowing rodents
take refuge underground; seals and whales live underwater. Humans, however,
bathe in sunlight—with inevitable consequences.
As decades pass, the collagen that holds our skin together becomes less
elastic. You can demonstrate this change by grasping a fold of skin
on the back of your hand. Pull it outward and then let go. Because their
skin is highly elastic, children and young adults will see it snap back
into place immediately. Older readers will note that this fold of skin
relaxes more gradually. The difference is due to age-related changes
in the composition of collagen. Decades of exposure to free radicals
(aggressive chemical compounds that can damage other molecules) gradually
modify the way our bodies can make and repair the collagen building
blocks that hold our skin together. Tobacco smoke is loaded with free
radicals, which is why smoking accelerates the loss of our skin’s youthful
suppleness. The warning label on cigarette packages could easily include
premature facial wrinkles as one of the many hazards of smoking.
So, what does it take to make a wrinkle? The essential ingredients include
- prolonged exposure of hairless skin to sunlight,
- longevity sufficient
to experience age-related changes in skin collagen, and
- exposure
to free radicals that can alter skin proteins.
The ideal candidates
for wrinkle formation are long-lived, hairless, terrestrial mammals.
Humans share these characteristics with just one other species. We,
like elephants, get wrinkles. If you have ever seen an elephant up close,
you have surely noticed its elephantine wrinkles. We are the elephant’s
dermatological first cousins. We are human pachyderms.
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