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When mummifying their kings and queens, ancient Egyptians would remove the brain and all the
internal organs, except for one: The heart.
Believing it held all thought and feeling, the deceased would need it in the afterlife,
when they… rose again.
By 2000 BC Chinese doctors had uncovered the heart’s role in pumping blood throughout
the body, Western thinkers from Aristotle to the Renaissance believed the heart governed
the emotions, a notion so powerful that it still persists today, in… a different form.
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The heart symbol’s resemblance to the real thing is… debatable. Its origins are uncertain,
but we see it as far back as the 6th century BC. Coins from Cyrene, in what is now Libya,
carry the familiar emblem, representing silphium, a now-extinct plant used as a cooking spice,
perfume, aphrodisiac, and… contraceptive.
In the 17th century, St. Mary Margaret Alacoque reported seeing a vision of the sacred heart
of Jesus, surrounded by thorns, and the symbol has since been associated with love and devotion.
Today we know that love, along with all of our thoughts, desires, and emotions, comes
from our brain, not our chest.
"Where is fancy bred… in the heart or in the head? Shall we roll on?"
I guess most people don’t find it that romantic when you say “I love you with all my limbic
system”.
But even though love lives among our neurons, we can feel it here in a very real way.
Physical pain activates the same regions of our brain as emotional loss. That neurological
stress can overstimulate the body’s vagus nerve, causing nausea, dizziness, and physical
pain… real, actual heartbreak.
It’s not all bad. When we see of a loved one, our brain stimulates the release of epinephrine
and norepinephrine from our adrenal glands, causing our heart to beat faster.
But yes, one can desire too much of a good thing. Heart rates of 200 to 250 beats per
minute could kill you or me, but to a pygmy shrew that would feel tame.
This thumbnail-sized relative of the mole has a resting heart rate of 1300 beats per
minute, about this fast. Even beating a hummingbird’s hyperactive heart, and more than 15 times
the average human’s.
A pygmy shrew will live just a year and a half, but in that time their heart will beat
about a billion times.
An elephant? About a billion beats. A rabbit? About a billion.
In fact, animals of all sizes seem to get about a billion heartbeats in a lifetime.
The heart isn’t some sort of ticking clock counting down to six feet under, but there
is some truth to the billion heartbeat hypothesis.
Because they have a larger ratio of surface area to mass, small animals lose heat more
quickly than larger animals, so they have higher metabolic rates and their cells wear
out more quickly. Scientists think that lower metabolic rates are directly linked with longer
lifespans.
As mass goes up, heart rates scale to the minus one-fourth power. So a cat is about
100 times more massive than a mouse, and its heart beats about one-third as fast. It works
for lifespan too, only larger mass scales to the positive one-fourth power. That cat,
100 times larger than the mouse, lives about three times as long.
Biologists call this the quarter-power scaling principle, for different sized animals, measures
of metabolism scale in multiples of one-fourth.
Except for us. We seem to be an outlier. Following that rule of size, we live about three times
as long as we should, we get about twice as many heartbeats as you’d expect. The advancements
of modern science and medicine have extended our lifespans… caring for one another helps
us live longer.
That’s a lovely thought. Stay curious.