|Why do we have not useful body parts in our body
that can be removed with no effect?|
|Question Date: 2017-09-12|
Great question, Rebecca. Evolution
shapes organisms into efficient beings, not unlike
factories strive to be efficient. Suppose your
business made cars. If you added parts to the car
that served no function, that would add
unnecessary cost. As a result, your company would
lose customers, and slowly you'd go out of
business. Organisms generally lack "useless"
parts, for the same reason cars do. Useless
parts put an organism at a competitive
disadvantage, making that organism less likely
to produce offspring compared to its more
Good question. There aren’t many parts
we can lose without it causing some problems, but
there are some. For example, “wisdom teeth” are
molars that we often need to have removed because
we don’t have enough room in our mouths for
them. But before tooth brushing and dental
visits, people probably lost more of their
permanent teeth, so they may have actually been
useful before not too many generations ago.
Tonsils are an example of something that
is useful, but we’re sometimes better off without.
Tonsils are part of our immune system. They help
protect us from the germs that are constantly
entering through our nose and throat. But when
they are swollen and painful too often, they can
be removed and other parts of the immune system
can take over their job pretty well.
The appendix is a small tube that comes
off of the place where our large and small
intestines connect. It is a dead end tube off of a
dead end tube, so sometimes things get stuck in
it. It can also get infected without anything
trapped in it. Sometimes it has to be removed when
that happens, but these days, they may just give a
person antibiotics to clear up the infection.
The appendix really has no function in us, but in
our ancestors, it was probably larger and was
important in breaking down plant material. The
appendix is very large in some animals that eat
Some people believe that these evolutionary
leftovers (also called “vestigial parts”)
will just disappear over the course of evolution.
This only happens if making or having those parts
is costly enough to make people with those parts
less likely to reproduce. But having tonsils, or
wisdom teeth, or an appendix rarely kills anyone,
and probably doesn’t make them less likely to have
kids. So future generations will probably have
Can you think of any other parts of the body
that seem useless?
Thanks for asking,
Your question is touching on evolution,
or the change in genetic traits of a biological
population across numerous generations. As
organisms evolve, certain features or body
structures may be lose purpose when it is no
longer necessary for successful continuation of
that organism. The loss of function may occur
due to a change in environment, such as the
development of impermeable eggs for organisms that
first began laying eggs on land (positive
selection), or due to a structure becoming
harmful, such as a mutation that causes
infertility (negative selection).
Sometimes a feature may be neither helpful nor
harmful, therefore it may not be phased out
through natural selection as its presence persists
across the generations. The retention of these
features that have lost some or all of their
original function through evolution is called
vestigiality. Humans maintain several
vestigial features: the tailbone (or coccyx),
wisdom teeth (or third molars), the inner corner
of the eye (or plica semilunaris), the appendix,
goose bumps (arrector pili), and tonsils.
Since these features are not advantageous,
it is alright if they are removed.
Body parts are expensive: they take energy
to make. Because it is more efficient
energy-wise to have only the body parts that you
need, natural selection favors those animals that
have only the needed body parts. Any animal
that has unneeded body parts will evolve to lose
Why would we have useful parts in our body
that can be removed with no effect? If we had
too many parts like that, we would be wasting
energy building them and keeping them alive,
and people without those body parts might evolve
and win out over the people who were wasting all
that energy on those body parts that aren't
On the other hand, things don't just disappear
from plants and animals because they're not used.
They only disappear if the plants or animals
without those things win out over the plants and
animals that have those useless things.
I think we actually do have some body parts
that can be removed with no effect. On part is
the appendix. The appendix can be removed
with no effect. The appendix is a tiny piece of
the intestine in humans that is much bigger in
herbivorous animals like the guinea pig, where it
is called the caecum ['SEE-cum']; and it
has microbes that digest all the cellulose the
guinea pigs eat in the grass they eat.
We used to think our appendix didn't do
anything useful, but now some scientists think the
appendix stores useful microbes that go into our
intestines after we have diarrhea:
Appendix (Anatomy): Appendix Picture, Location,
Definition, Function ...
Another body part that can be removed is the
kidney, because people can donate a kidney to
And our wisdom teeth can be removed without
Hello! You’ve asked a really interesting
question that plays into the mechanisms of evolution.
Evolution is the process by which organisms
change through generations in order to be better
suited for their environment. The way this
works is that organisms with traits that help them
survive better will be more likely to have
children and pass these traits onto the next
Imagine an especially long-necked giraffe that is
able to reach more leaves. It will be healthier
than the other giraffes because it is able to eat
more. Since it is healthier, it is more likely to
have more children and pass on its long-necked
traits to its children. An important idea to note
is that traits will only develop if they
ultimately help the organism produce more
This preliminary explanation may have seemed
unrelated, but let’s get back to your original
question. These body parts that are not useful to
us anymore (called vestigial structures)
were at one point useful in our ancient ancestors.
Our appendix used to aid in digestion when our
diets were different, but now it is no longer
useful. Having an appendix didn’t hurt people, it
just did nothing. Since people who were born
without an appendix aren’t any healthier (and by
extension, can produce more children) than people
who have their useless appendixes, there’s no
evolutionary drive to remove the appendix.
This goes for any other vestigial structures;
there’s no reason to remove them!
As a fun fact, I’d like to add that many other
animals have vestigial structures. One of the most
bizarre is the pelvic (hip) bone in whales.
Whales evolved from land mammals so they used to
have legs. At some point they returned to the
ocean and their legs shrank through generations.
At some point they disappeared completely but it
was never advantageous to remove the tiny pelvic
bone so they still have it. Thank you for your
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