|Why humans do not have tail?
|Question Date: 2014-08-16|
I think it would be really cool to have a tail
that could grab onto things (a prehensile tail).
Unfortunately, humans and our closest relatives
(the apes) don't. We do have what's called a
"vestigial" tail, meaning that it's a sort of
evolutionary leftover. It's visible in embryos,
but by the time we're born, we just have a few
small bones that can't be seen from the outside.
Most people don't even know they have tailbones
unless they break one. Occasionally, a baby will
be born with a tail, but it is usually removed
Why did the ancestor of the apes and people
lose their tails? No one really knows. Things
don't disappear just because they are not being
used. One gene can cause many different things. It
is possible that a gene that was helpful to this
species had a few effects, including the loss of
the tail. It is also possible that having a tail
came with a price. Individuals that had small or
no tails would have been able to leave more
offspring with the no-tail gene. Can you think of
any ways that a tail might be a problem?
People often confuse apes (chimps, gorillas,
orangutans, gibbons, etc.) with monkeys. They're
not. Apes don't have tails.
Thanks for asking,
A very interesting question with a subtle answer.
If you look at the end of the spine of a human,
you'll find a peculiar feature....
here to see, please
There is something that looks strikingly similar
to a tail, which is appropriately named the tail
bone (aka coccyx); in rare cases, some people are
born with something tail-like, which is considered
a congenital defect. So, what is this tail bone
It is accepted that the tail bone is vestigial,
an organ or trait in humans that have lost their
original function through evolution. The tail bone
is actually a part of a larger group of features
that have gone out of use. You can read more about
You may even be familiar with other vestigial
parts of the human body, such as the appendix or
wisdom teeth, which people often have removed for
health or medical reasons.
Why did the tail bone become a vestigial
There are several theories as to why this
happened. If you think about a few animals with
tails, you might notice that they tend to move on
four legs (e.g. cat) or use the tail itself for
locomotion (e.g. fish). Tails in animals are
observed to have function, such as balance, brush
away insects, or grabbing things. A possible
explanation is that humans became bipedal (i.e.
walk on two legs) and so the need for a tail faded
Why did humans become bipedal?
There are also a lot of theories for this as well.
You can read a more in-depth article click
here to read article.
Theories range from being able to carry
objects (the wonders of opposable thumbs! There's
even a whole Wikipedia article about the thumb)
to exposing less surface area to the sun where
there's a lot of sun.
Here's an excerpt from the hyperlinked article:
Twentieth-century theories proposed a wide
array of other factors that might have driven the
evolution of hominin bipedalism: carrying objects,
wading to forage aquatic foods and to avoid
shoreline predators, vigilantly standing in tall
grass, presenting phallic or other sexual display,
following migrant herds on the savanna, and
conserving energy (bipedalism expends less energy
than quadrupedism). Furthermore, if the early
bipeds were regularly exposed to direct midday
tropical sunlight, they would benefit from
standing upright in two ways: less body surface
would be exposed to damaging solar rays, and they
would find relief in the cooler air above the
Who knows, with a few more years of evolution, the
tailbone might disappear altogether! What do you
think could end up being like a vestigial trait
with our ever changing lifestyle and usage of
Hope this helps!
Humans are apes, and apes for reasons of evolution
that are not currently known have lost their
tails, unlike their closest relatives, the
monkeys, who still retain their tails. Sometimes
humans are born with very short tails, but they
are cut off by the doctors when it happens.
The easiest answer to this is that there was a
genetic pressure to no longer have a tail. That
means, at some point in evolution, it became more
favorable for survival to have no tail. Thus,
monkeys without tails were more successful at
reproducing, creating more monkeys without tails,
and leading them to take over. What was this
pressure? We don't know for certain, but with our
ancestors being able to swing from trees with
hands, tails became redundant and a waste of
energy. When walking, we also did not need tails.
So, it became more common to not have tails over
millions of years.
What is REALLY crazy is that the genes that
make tails are turned off in humans, but random
mutations in a baby's development can turn them
back on. This is probably how we lost tails in the
first place (random mutations turning off tail
development). But even today, very very rarely a
human will be born with a fully functioning tail.
This points to our evolutionary past, but can be
pretty scary for parents. This has happened over
20 times in the past 100 years.
here to read more
This is an interesting question! Actually, a
tail is present for a few weeks during human
embryonic development, and is most visible around
the time the embryo about 31-35 days old!
Eventually, however, the tail disappears and all
that is left is the coccyx, which is a sort of
"vestigial tail" if you will. The coccyx itself is
a point of attachment for several soft tissues,
such as muscles, ligaments, and tendons.
While the answer to your question is not known
exactly, it may be useful to think about what
other animals use tails for. Depending on the
animal, tails can be used for balance, as
something to rest on, for swatting insects away,
keeping cool, or as an extra appendage that can
grab/hold things. Because of our bone structure,
we are able to balance without a tail. We also
don't need a tail to swat insects away or grab
things, because we have hands (with opposable
thumbs). So, having an extra body part that that
does things other body parts can do just as well
would be costing the body extra energy to sustain
that part without it actually doing anything
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