From Wikipedia:

Human embryos have a tail that measures about one-sixth of the size of the embryo itself. As the embryo develops into a fetus, the tail is absorbed by the growing body.

How are we sure that it is a real tail and is not a superficial resemblance of something else?

I ask this because some creationist guy challenged me in this regard.

  • 2
    $\begingroup$ I just want to ask one thing: what else could it (tail-like thing) be, another hand or another leg? $\endgroup$ Mar 28, 2016 at 7:59
  • 7
    $\begingroup$ It is an extension of the vertebrae. Isn't that a good reason? $\endgroup$
    Mar 28, 2016 at 8:31
  • $\begingroup$ @user40602 If you consider your question has been answered, you can check your favourite answer. $\endgroup$
    – Remi.b
    Oct 14, 2017 at 15:43

3 Answers 3


We can be sure it's a tail because it is an extension of the vertebrae, and we define "tail" as an extension of the vertebrae, among other things.



noun: tail; plural noun: tails

  1. the hindmost part of an animal, especially when prolonged beyond the rest of the body, such as the flexible extension of the backbone in a vertebrate, the feathers at the hind end of a bird, or a terminal appendage in an insect.

Emphasis mine. Source: www.oxforddictionaries.com

  • $\begingroup$ Some mention of the identical embryology would make this better, the human tail is not just a tail because of its location. not all tails are the same. the human tail is homologous with other vertebrate tails. $\endgroup$
    – John
    Apr 12, 2019 at 21:42

Well, what would you call it? Have a look at the images below (source):

carnegie collection embryos

If you would call what other species have tails, then the human one should also be called so. After all, they are extremely similar (the last image, k, is human):

Mammalian embryos

a Echidna or spiny anteater (Tachyglossus aculeatus). Because of the extreme rarity of monotreme material we were only able to obtain this embryo, which is younger than the tailbud stage. b Brush-tailed possum (Trichosurus vulpecula). c Eastern Australian native “cat” (Dasyurus quoll). d Domestic cat* (Felis catus). e Domestic dog (Canis familiaris). f Domestic sheep (Ovis aries). g Scaly anteater (Manis javanica). h Rat (Rattus norvegicus). i Rabbit (Oryctolagus cuniculus). j Hedgehog (Erinaceus europaeus). k Human (Homo sapiens).

The above image was taken from M.K. RIchardson et. al.,Anat Embryol (1997) 196:91–106 (a PDF can be found here)



Let's start with a fun fact!

In some rare cases, humans can get born with a tail. These tails can then be removed by surgical procedure. Such procedure are quite simple and are a relatively old procedure (see Speigelmann et al. 1985).

What is a tail?

The tail is the section at the rear end of an animal's body [..]. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds

Source: Wikipedia

Sacrum and Coccyx are the last parts of the vertebral column. A tail is therefore, just an extension of the vertebral column.

How does it look like in humans?

enter image description here

enter image description here

Is it really a tail that we see?

Yes! Human embryo have been dissected and histologic analyses were performed. There are no doubt, it is a tail!

See Dao and Netski (1984), Belzberg et al. (1991) and Fallon and Simandi (2005) for further description and evidence.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .