Why don't humans walk on four feet?

Question

My 10 year old daughter wants to know!

Answer 1

Because we only got two. Children need rational answers to develop their imagination. What if... Imagine if...

Answer 2

Here's what probably happened:

1) The species that humans originated from were ape-like, and used their hands and legs to walk on the ground on the occassions that they had to.

2) As that species' enviornment changed from many trees to fewer and fewer trees, the ape-like species had to move to the ground more and more often.

3) As they lived more and more of their life on the ground (as there were fewer and fewer trees in their environment), they had to be able to do things differently. For example, they had to be able to see land based predators (lions, other ape species, etc.) without the benefit of a tree to climb. Those that could stand up on 2 legs and see over the high grasses had a better chance at spotting predators earlier, and could get away sooner, and had a better chance at survival. They also had to see over the grasses to get a better view of prey; the more prey they could hunt, the more food they had for their social group ("family"), the more they impressed the opposite sex and mated, etc.

4) Because this happened over hundreds of thousands of years, the traits and the things that arose because of those traits (the increase in brain size, the use of tools, the care for children) they built up until in the species until we became what you see today.

Probably not the greatest answer for a 10-year old, but pretty scientifically accurate, according to evolutionary theory. Or, you could just tell her it's because we only have 2 legs, and give her this answer when she's ready for it.

Answer 3

We used to walk on four feet, if you believe the evolutionary theory. Several still-existent aspects of our body point to this fact, that we used to be built like other animals. But humans, having developed a larger and more complex brain, found other ways to survive. Gradually we started using tools and other things, and we needed to free our hands, so we, more or less, 'stood up'. That's what science says we did. It was probably more gradual than that, of course, but that's the idea.

We used to walk on all fours, then we learned to walk on two so we could do stuff.

Answer 4

It may be because as human brains grew larger, babies were born more helpless (being born before fully developed so the brain could do a lot of growing outside the mother) and mothers had to walk more upright in order to carry a more helpless baby.

Many think upright walking occurred because the males had to hunt and protect the females, but it seems to me like the need to carry more helpless babies makes more sense. Maybe you will tell your daughter for me that we need more women studying these things so we get a better female perspective!

Answer 5

It's because of evolution, correct.

Humans actually started moving with bipedal motion before the brain became more specialized. The advantages to walking upright allowed us to see further, so that we could either hunt better for prey or escape predators. It's much easier to stand up than to climb a tree. Also, it allowed us to carry things - food, weapons, babies - which was especially convenient, thanks to our opposable thumbs that are used for grasping.

There is strong evidence that our ancestors did walk on all fours. Our bone structure is similar to that of other mammals that are quadripeds. Other primates occasionally or always walk on all fours. The common and excessive problems that humans have with their backs is a result of adapting a structure that was meant to be quadripedal to that of a bipedal organism. The bones weren't meant to walk upright; it puts too much pressure on lower backs and knees. However, evolution has to work with what it has, so here we are today.

Answer 6

The erect posture, bipedal locomotion, is precisely what freed the hands to carry objects, allowing the specialization of the upper appendages as effectors; to touch, feel objects, build tools, carry things, and use weapons.

As long as our ancestors used all 4 limbs to walk, they were prevented from evolving to the level we are now. What triggered this is the climbing in trees of apes, with an eventual stop of this tree climbing life; meaning that some land dwelling apes found themselves with hands that were not really required to climb up trees all the time anymore.

Answer 7

we don't walk on four feet because we were created by something. That something is GOD. In the bible it says we are created in his image, which means to a point we all look like him but different from him. There may be a scientific answer out there, but its wrong, this is the easiest answer to that question, and i cant believe the scientists don't even see it or let alone acknowledge it.

Answer 8

Well since it´s your daugther :) just tell her it´s really hard on her jeans. But this is of course due to evolution, me not being so smart when it comes to the history of man and our evolution....I´ll let someone else answer this one ;)

Answer 9

Check out this website for some indepth information regarding your question: http://education.yahoo.com/reference/encyclopedia/entry/humanevo

Answer 10

Because we have adapted to our surroundings and become bipedal so that we have hands to carry stuff.