Science
Knows Why ...
- You get goose bumps. When you
feel a chill or see something scary,
your body releases a surge of adrena-
line. The point is to make your body
hair stand up—which helped our
animal ancestors stay warm and also
made them look larger in the face of
predators. Getting those individual
hairs to stand at attention requires
the teeny skin muscles at the base of
each follicle to contract, making your
skin look vaguely like a goose’s post-
plucking—hence, goose bumps. - You grow wisdom teeth. Wisdom
teeth are actually a third set of mo-
lars. They allowed our forebearers to
munch on rough food such as roots,
nuts, and meat, especially when other
teeth fell out (alas, our ancestors had
poor oral hygiene). About 35 percent
of people never develop wisdom teeth,
partly because of an evolutionary shift
that means the human jaw is often too
small for them. The rest of us start de-
veloping them by age ten, though they
don’t fully emerge until young adult-
hood, which is when we (allegedly)
acquire full-grown wisdom.
3.Your fingers and toes wrinkle in
water. When you’re in the bath, water
seeping into your skin makes the up-
per layers swell. That causes the bloodvessels below to constrict, which in
turn causes some of the upper lay-
ers of skin to collapse. The irregular
pattern of swelling and falling skin is
what we see as wrinkles on our finger-
tips and toes.- Your knees crack after sitting for
a long time. The sounds you hear
are probably caused by gas being re-
leased from the spaces between your
joints—just like when you crack your
knuckles. Meanwhile, muscles or ten-
dons rubbing against your bones may
also make your joints creaky. “We say
motion is lotion,” Kim L. Stearns, MD,
an orthopedic surgeon at Lutheran
Reader’s Digest
58 june 2019
No.5
What
Gives
Yo u a
Stitch