Just as the title says. Why do some organs come in pairs, but others come singly? What happens during the development of an embryo that causes two or one organ to develop?
Perhaps, but the mouth and sex organs have bi-lateral symmetry. Just like the body does with those organs we have two of.The evolution of two eyes seems very reasonable since depth perception is useful for both predator and pray, but I can't think of any reason why two mouths would be all that useful and two sex organs would just be damned confusing.
Well, obviously, but I was hoping for a little more detail you mangy mutt, you! *smacks Phinds with a newspaper* Off to the bath with you!As to why the embryo develops that way, that just genetics. It's evolution that causes the genetics to be that way.
By "Darwinian experiments", I was referring to the results of evolution. So my citation is you, in the corporal sense.Got any references for that, Scott?
That's not how it works here at PF. Do you have any actual references that support your explanation? Something that elaborates on what you've said? I'm just looking for something more detailed than general explanations, not contesting your post.By "Darwinian experiments", I was referring to the results of evolution. So my citation is you, in the corporal sense.
Do you mean the hypothalamic-pituitary complex? How does this region have any more of a tightly integrated form of redunancy than any other region? You need to provide references if you're going to make assertions like that.But the parts that decide when we're too hot, too cold, or too hungry, or control out sleep or blood pressure have more tightly integrated forms of redundancy.
That's an unsubstantiated hypothetical claim as far as I can tell. If we were to duplicate our already paired spinal columns, that would confer a measure of signal traffic confusion that would be unworkable. Nature would have selected that out immediately.We could have two spines carrying redundant data - but there would still have to a single decision point in the brain feeding both spines and muscles would have to decide while spine to listen to.
The entire neuraxis is a paired structure. It's not as if we have a paired left brain hemisphere and right brain hemisphere, and a single spinal column. The spinal cord also has a paired division, just like the brain. While motorically one hemisphere of the brain-spinal cord controls the contralateral half of the body, there is also a smaller measure of ipsilateral control which may serve a role of redundancy, but that is a matter of some speculation.According to the Darwinian experiments, one well-protected spine provides a better pay-off than redundancy.
That was my point, nature did select it out immediately - or quickly enough.If we were to duplicate our already paired spinal columns, that would confer a measure of signal traffic confusion that would be unworkable. Nature would have selected that out immediately.