IDIOT’S GUIDES: SCIENCE MYSTERIES EXPLAINED
Why can’t birds taste chili peppers?
Unlike mammals, birds can gobble as many crazy hot chilies as they like, straight from
the bush. They simply don’t feel the burn. Why not, and why is the chili plant so selective
about whom it tortures?
Birds lack the taste receptors on their tongues to feel the burning sensation from chili. Humans do have
the receptors and can feel the pain. Lots of pain! But ironically, chili may have a medical role to play in pain
One of the fascinating things about the plants we
eat is that many of them contain toxins the plant
has spent millions of years evolving—just so ani-
mals like us won’t eat them!
Only humans seem to be perverse enough to
actively seek out plants that actually hurt us to eat.
Little does the poor chili realize, but the correct
amount of capsaicin (the chemical that makes the
burn) actually enhances the ﬂavor of carefully pre-
pared meals. But only because humans are crazy!
As anyone who has been naughty or unlucky
enough to be hit by capsicum spray will agree, cap-
saicin burns any tissue it comes into contact with.
The plant is deﬁnitely sending us a message: don’t
eat my fruit!
Birds don’t get that message. Their taste
buds don’t react to capsaicin. It simply doesn’t
register in their mouths, and so birds can hap-
pily eat chilies with no ill eects. Later, the bird
ﬂies o, poops out the seeds, and a new chili
plant germinates. Everybody wins!
We mammals, unlike birds, have a nasty
habit of chewing our food, and our powerful
back teeth grind up and destroy many seeds.
Chili plants evolved capsaicin in their seeds
to discourage mammals from eating the fruit.
Plants without capsaicin got munched by an-
cient herbivores and didn’t propagate as widely
or successfully as those with spicier seeds.
Humans have learned to love the burn of
a good chili. As far as we know, we’ve always
enjoyed spicy food. Part of the explanation may
have to do with the way the brain releases en-
dorphins as the burn of the capsaicin fades.
Humans actually compete with each other to produce
the most powerful chili-based concoctions, ranking them
on the so-called Scoville scale. Tabasco® sauce has a rating
of 2500–5000, cayenne pepper 30,000–50,000, habanero
chili 100,000–350,000, and the Trinidad moruga scorpion
(a new variety of chili, not a killer arachnid) tops out at a
face-melting two million.
One step up from crazy foods, we use capsaicin as a
nonlethal weapon, spraying it in the eyes of rioters or
rowdy criminals in hope the tears and pain will convince
them to mend their ways.
Oddly, though, hyper-concentrated capsaicin can also
be used as a painkiller. It works basically by overloading
pain receptors so you don’t feel pain while the capsaicin
is on your skin. Note: you’ll get a topical anesthetic from a
nurse ﬁrst. Without it, this particular cure would be worse
than the disease.
It’s also possible that capsaicin has an important role
to play in reducing cancer tumors, and even curing leuke-
Incidentally, chilies feel hot because the capsaicin
causes certain pathways in your pain receptors to open.
These pathways normally don’t open unless your skin
gets very hot—114°F, to be precise. Capsaicin makes the
channel open even when your skin is normal body tem-
perature, which is why you get the false sensation of real
heat on your skin or tongue if you come in contact with
Human Tongue Cross-Section