All across the animal spectrum, you’ll find tails. Fish have them in the water, birds have them in the air, and land creatures have them. There are even some animals where you can’t easily tell where the tail ends and the body begins, like snakes, worms, and eels.
It is actually pretty difficult to come up with an animal that doesn’t at least have a stump of a tail. The octopus doesn’t have a tail, nor do frogs. However, the animal family that has universally gotten rid of their tails is Hominidae. There aren’t many creatures in this family, just the orangutan, bonobo, chimpanzee, gorilla, and us. Yep, this is our extended family – a bunch of fascinating members without a tail in sight.
How and why did humans lose our tails?
What happened? How did we evolve into this family of tailless creatures that are clearly so different than other animal families?
The easy answer is mobility.
The full answer is a good bit more complicated since the changes came about over tens of thousands to hundreds of thousands of years. It’s also something that can only be explained through speculation.
1. It’s about mobility
Tails provide stability when animals are moving, as well as providing additional maneuverability. When you watch large cats chasing down prey on TV, they are putting that long muscular tail to work helping them shift their balance to change direction.
For other primates, like lemurs and monkeys, the tails provide greater mobility in the trees too. Or, if you’ve seen squirrels running along branches and jumping from tree to tree, you’ve seen just how their tails move and help them quickly navigate through highly difficult situations. And they look very comfortable doing it.
2. It’s about balance
Despite what has been said in movies, the average human head actually weighs around 11 pounds. Between the dense brain and the bony skull, there is a lot of weight housing the part of you that controls everything else in your body. It’s not just humans that have heavy heads, but a universal fact for the vast majority of animals.
Consider that most land animals walk on four legs. This means that there is a lot of weight that has to be balanced on their front legs. The tail provides a way of offsetting some of that weight.
When Hominidaes started walking in a more upright position, the shift in posture significantly shifted the balance of the head against the rest of the body.
3. Walking upright
Animals that are able to walk in an upright position don’t need the benefits of a tail. Gravity takes care of balance as that heavy head is evenly balanced over the full body. In fact, this is one of the biggest benefits of walking upright – gravity takes care of most of the work.
Animals that walk on four legs expend a lot more energy to balance those heavy heads. The tails compensate, but it takes more energy to move around on all fours – gravity is working against them.
It’s also important to remember that gravity is also compressing your spine when you walk upright – which isn’t as much of a problem for most other animals. Good posture and not staying in one position for long periods of time can help to alleviate problems with your spine.
4. Other uses for tails
While tails work as a way of improving balance and mobility, animals have become very creative with how they use tails. When you think about monkeys, you know that they have prehensile tails that work in ways that are similar to hands. This is a very unique and specific use that few other animals have adapted.
More often, tails are used as a way of slapping away bugs. Horses, elephants, and other large animals have hairier tails to whip little pests away from their bodies.
Kangaroos have their own unique use for tails – they allow kangaroos to more easily fight. By balancing on their tails, they can use their powerful legs to “box” other kangaroos or animals, sometimes to devastating effect.
Dogs have famously learned how to communicate their emotions with their tails. They let us know that they are incredibly happy to see us, or they can warn us when they are angry. You do have to read other body language clues from them to know what their wagging tail means, but the movement will definitely catch your attention so that you know to actually look for those other signs of what that tail is trying to convey.
5. Humans have other solutions
No matter how many fascinating uses other animals have for tails, humans have other solutions to all of those problems. Since we walk upright, we have hands to grip things or to fight – though we are admittedly not nearly as effective as kangaroos. And we make tools to get rid of bugs.
By walking upright, we humans have literally freed up our hands to do so many other things. With our hands free, we didn’t need to find other uses for tails, so over time, they got smaller and smaller until they were gone.
6. Trying to pinpoint when
When humans lost their tails is nearly impossible to determine. After all, we still have remnants from our tails in the form of the coccyx, better known as the tailbone. Given that being tailless is pretty universal for all of the animals in our family, it is hard to know exactly when Hominidaes started losing their tails. It is thought that apes started to really get rid of their tails when they started walking upright. Over time, tails became unnecessary, shrinking until a genetic mechanism kicked in and the tail stopped growing altogether. We still have tails as embryos, but in most cases, the tail is gone by the time we are born.
It may be a bit of a bummer, but humans aren’t likely to get their tails back since we don’t really need them. Now, all we can really do is imagine what it would be like, then enjoy the full use of our hands, our own very unique appendage that is rare among animals.