If humans spent their first 9 months of existence in fluid, why can't we breathe underwater?

Question

I know no one really knows the answer but have any of you ever thought about this?

Answer 1

Although it would seem logical that the gills which appear and disappear in the course of mammalian (including human) embryotic development would transform into lungs, as Dr. What suggested, lungs actually evolved from swim bladders used by fish to adjust their density helping them to go up or down. Gills work on a different principle from lungs in order to transfer oxygen from one liquid to another, which is of no use to air breathers, whereas swim bladders provided a ready-made air-filled cavity that transfers air in and out of the blood for evolution to work with. Bird lungs, perhaps not surprisingly, work on a sort of reverse principle from those of humans, wrapping the air passages around the blood vessels rather than the other way around, making bird lungs much more efficient and less prone to problems, which is why birds can easily go up and down without suffering ill effects that humans suffer when they try to go up too fast.

Regarding the answer to this question in particular, the umbilical cord of course is the right one. Human fetuses don't absorb air from embryotic fluid. For one thing, the embryotic fluid lacks Hemoglobin, the iron-rich vehicle for carrying oxygen. Rather, fetuses get oxygen piped in from the mom in her blood through the umbilical cord, by the same vehicle that the mom's own cells are supplied with oxygen (thus requiring no additional mechanisms of moving oxygen into yet another liquid). Along with nutrients the oxygen crosses a membrane into the fetus's blood. Sometimes blood leaks across the membrane. If the mom's and baby's Rh types are incompatible, the mom can suffer a rather to painful death, something that happened to a family friend of my wife many years ago. Modern medicine luckily has made available preventive intervention. Carbon dioxide and other wastes are transferred the other direction from the embryo's blood back into the blood of the mom, who then expells the embryo's wastes along with her own.

Answer 2

Pretty simple.  In the womb, we are getting our oxygen via the umbilical cord not the mouth,nose or lungs.  Without an umbilical cord attached to someone who can breathe the air with a mouth and nose and process the air in the lungs, we are lost.

However, there is a procedure I've read about with preemie newborns that puts them into a breathable fluid to help their tiny lungs develop.

Answer 3

because their lungs were not inflated with anything before birth.they got every thing through the umbillical cord

Answer 4

We can breathe underwater - using SCUBA gear. However, we can not breathe water.

Answer 5

We could breath underwater but we couldn't survive long.  We can't extract enough oxygen to survive because the density is too high.  It would also rapidly mess up the electrolytes in the blood.  There are some fluids that can be breathed for a time.  They are usually a perfluorocarbon.

http://en.wikipedia.org/wiki/Liquid_brea...

Answer 6

The amniotic fluid is not water.  In the womb, we obtained oxygen via the umbilical cord, not via our breathing methods outside of the womb.

The only liquid we can breathe is liquid oxygen.

Answer 7

...iunno...a teenager can only know so much in his free time...

Umm ima go with.

The fluid we are in isn't really water, I think. Maybe the fluid has some special proporties that allow the babies to live?..

Ugh..

Answer 8

I actually had a biology professor address this question, and the answer was really surprising.

It turns out we sort of could.  At least our lungs would be able to extract oxygen from the sea water (regular water wouldn't work).  

The first  problem is that water is much much denser than air, and our diaphragm is not strong enough to suck in and blow out enough water to keep the oxygen levels high enough to support life.

If there was a superhuman who could keep the water moving, they would run into the second problem which is that they would never be able to return to breathing air, because they wouldn't be able to clear the water from the deeper parts of their lungs.

Who'da guessed.

Answer 9

our gills evolved into lungs.

Answer 10

We had an air-tube with us for those 9 months though.  If you need to see evidence, look for that little hole in your abdomen.

We got all the O2 & nutrients we needed; and we sent out all the waste through it.