Why dont humans all have tails?

Question

I accept the theory of Darwin`s evolution/”survival of the fittest”. However, I do not understand how a non-life threatening evolution can take place, for example as I hear, in our own evolution we lost our tails. How would having a tail be life threatening and not always be an advantage?

OK, we lost the "need" for them. We also dont "need" eyebrows, the appendix, tonsils or male nipples. Why do we have those but not a tail, which would add to our lives? I cant see how those without tails would have an advantage.

Is not "needing" something consistant with the harshness of "survival of the fittest"?

I wouldnt have died because I had a tail. If we all stopped using our left arm, would it drop off? How and why?

Answer 1

Losing something like the tail doesn't always happen because it is detrimental in any way. It can simply be that a mutation happens that is simply not harmful - ie neutral.

One of our ancestors had a mutation that caused it not to develop a tail (probably several ancestors and several mutations, but this is a simplifcation). Because the creatures were no longer living in trees, losing the tail was neither good or bad - it was neutral. And because it didn't actually harm the individual animal, it successfully bred and passed on the trail to its descendants - and it eventually spread amongst the whole population.

Another excellent example of a mutation due to this process is our inability to manufacture vitamin C. Almost all mammals have the ability to make the vitamin in our bodies. However in one of our ancestors, the gene responsible for this mutated and no longer works. However, at that time the creatures were living in forests and lived mainly off fruit, which contains plenty of vitamin C - so losing the ability to make it ourselves didn't matter. However, millions of years later when descendants of these animals - now humans - took to the seas for long voyages, scurvy began to be a problem because people weren't getting enough vitamin C from their diet.

So here we can see the development of what is now a harmful trail from something that was initially neutral. Don't forget that evolution doesn't care about the "best" result - just what's good enough for survival.

Answer 2

Tails were required as balance and supports for when we lived in trees.
I agree with the Daniel R when he said that the lack of a tail was a random mutation that spread down the generations.

However, I think that the lack of tails was also partly to do with humans starting to become bipedal (i.e. walk on two legs).
A tail is detrimental to this as it requires a slightly different positioning and layout of the spine.

Bipedalism the first thing that separated chimps from anatomically modern humans.

Unfortunately, I can't tell u if the mutation for lack of tail came before the impetus (whatever it was) for bipedalism.

So, we lost our tails.
Tails may have been life threatening as they impedded our ability to walk upright and on two legs.

However, if we lost our tails first, then its a blooming good job, cos we wouldn't be talking about this right now if we hadn't! We'd still be in the trees eating each other's fleas.

Answer 3

some people are born with tails,but most of use loss ares when in the womb, having a tail would be very difficult you would get it caught a lot and you would have to change the style of your cloths as so the tail would fit comfortable . And it would not look very nice on a man a tail hes already got one so two would look horrilble ..

Answer 4

Ground living primates don't need them. Not for balance, not for signaling. A few still have them, baboons do I think, theirs are sort of abbreviated.

An appendage that doesn't serve to enhance survival rates is open to being altered. Either co-opted for some other purpose or just being minimized into non existence. Maintaining a complicated body part that serves no purpose and is generally a liability is a waste of metabolic energy.

Our posture would make even a short tail troublesome. It would get in the way when we go to the bathroom, would be unhygienic if it pointed downward and easily injured if it stuck outward.

A giant elongated finger sticking out of the back of your pelvis, filled with fragile bones, fine capillaries and sensitive nerves, one you couldn't see without awkwardness. Not needed for balance in running or climbing, not prehensile, we weigh too much for that to work. Just something to burn vital resources that our brain would be robbed of, something to get damaged and get infected.

Answer 5

Mornin'

Don't know about all of that, but there was a bodybuilding programme on UK tv last year that showed a female British bodybuilder going over to the USA for the World Championships.

She got 'ripped' SO MUCH that you could see quite clearly the part of her body where her 'tail' would originally have been!

It was HORRIBLE!!!

Answer 6

We we all had tails before when we were climbing trees where tails were extremely useful. As we stopped that behaviour, tail has lost it's significance and slowly disappeared into the body. The remains of it is called appendix.

It's nature's rule that anything that has no purpose has to get destroyed.

Imagine now having tails. It will be extremely difficult to maintain them. At least we can't drive the car properly... and it's easy to pull someone...

Answer 7

It's more of a case that the tail was no longer needed. Where we developed the use of our hands, and become bigger in mass, that little tail would become useless, whereas those little ancestors used their tails to move things or reach for food, the bigger evolved ancestors would use their hands, and their intelligence to find other ways to get by.

Answer 8

River girl is right, even though somebody rated her answer as bad. Human embryos have tails in the early stages of development. The tail shrinks and is absorbed by the embryo as it grows.

Answer 9

Because we have evolved a complex vocal ability in which to communicate with each other. Dogs ect use their tails for balance and to show different emotions.

Answer 10

Well, if we had tails then we would get them caught in doors and stuff. So in a way it would be life threatening.