Evolution of blood

Factual Questions
1

I know that many people who deny evolution have trotted out the eye as a complex organ that could not have possibly evolved in stages, and that in response, there is an evolution book which directly addresses the issue of how the transitional stages of the eye could indeed have been viable organs. Fine.

But recently, while reading about a shortage of blood-bank blood, it occurred to me to wonder if there are any prevailing theories on how blood could have evolved in stages. After all, blood as a transport medium (let’s momentarily forget its infection-fighting function) is a very specific formulation, but such a complex one that even with gallons of blood available to copy from, scientists are unable to replicate its properties artificially. Yet somehow, the first species with a circulation system (earthworm types?) must have evolved the correct formula for nurtient/oxygen/waste product transportation at random, because if it got the formula wrong, it wouldn’t be able to convey these vital substances to the proper parts of its body for handling them. And that ignores the fact that said circulatory system (heart, arteries, veins, capillaries) had to be in place as well, because what survival benefit would the production of the proto-blood substance be to the creature if there’s no delivery mechanism? And what benefit would the delivery system be if it evolved prior to the delivered substance?

I’m not trying to start a debate here, and I’m not trying to be some anti-evolutionary “witness.” Most SDMB regulars know my religious beliefs, and I’m leaving those out of this post. I’m asking, out of sheer curiosity, if there are any theories as to how creatures with circulatory systems developed, in stages, from creatures without.

2

After studying Zoology, I can see how various systems of modern animals evolved. Earth still has many creatures that stopped at lower rungs of the evolutionary ladder, giving examples of how our predecessors might’ve looked and functioned.

One of the comparisons my teacher made was to compare the human embryo to theoretical ancestors of humans.
[ul][li]A 1-cell creature (protozoan) relates to a just-fertilized egg[/li][li]A many-celled polyp (jellyfish and their kin) compare to an undifferentiated hollow ball of cells at the next stage of embryo development[/li][li]Hi, Opal.[/li][/ul]
and so on. There’s even a point where the human embryo has 10 bones, 5 per side, on the face laying parallel, where fish then develop gills. But instead of gills, two pairs of them become the lower jawbone, and 3 pairs become the middle ear bones: hammer, anvil, stirrup.

3

I have started a thread with a very similar topic in GD called “Evolution Mechanics” here:

http://boards.straightdope.com/sdmb/showthread.php?threadid=78775

I have a theory on blood. Life originated in the oceans. Even today our blood has many of the same characteristics as sea water (similar pH, concentrations of a few salts, etc.) The first then life did (arguably) is develop a cell membrane. This closed off some of the surrounding water for the proro-organisms use. This is where the nutrients, proteins, nucleic acids, etc. were.

As multicellar life developed, a mechanism was needed in order to exchange resources between the cells. This isn’t all that complicated. Just more membranes to prevent the stuff from leaking out into the surrounding environment. The fluids were exchanged by osmosis.

Then life got more complicated with muscles and such. The movement of the organism itself would slosh the fluid around when cells squeezed together. Over time muscles developed for the sole purpose of squeezing memrbanes for better circulation. A rudimentary circulation system. Insects have something similar to this. Their heart pumps blood in and out of a central cavity (like a swimming pool pump) and the internal organs are literally bathed in the insects blood. From here its a small step to evolve the more complicated circulatory systems of the vertebrates. Remember that creatures didn’t appear on land till they could take a bit of the sea (their blood) with them.

The blood evolved at the same time. As the circulatory system developed and organisms got more complicated, dedicated cells were needed. They behave much like single celled organisms. If you take away the red and whites what you have left is quite a bit what we believe the tidal pools where life first appeared were like.

I assume blood is so hard to reproduce because of the erythrocytes (the red ones). These come from stem cells in the bone marrow and have no DNA of there own. How the *$#@& stem cells can be cultured or reproduced is well beyond us right now. (and a different topic entirely). Without the cells they might as well use saline (and they do).

As far as the evolution of the eye goes, check the top of this post for the link, it might give you a better starting point.

-Beeblebrox

“What the hell, he thought, you’re only young once, and threw himself out of the window. That would at least keep the element of surprise on his side.”

4

Sorry about all the &*#@# typos

5

This site has some interesting info on blood, and has this to say about blood evolution –

“In the more primitive beings, the liquid which flows among the cells has a composition very close to that of the water and performs modest functions. If you go up the evolutionary tree, this liquid assumes new and more complex functions. While in the invertebrates, the blood, called hemolymph, wet the organs and only in a part flows inside vessels, in the vertebrates blood flows in a vascular system which is entirely contained by walls and the cells are wetted by lymph instead. In the vertebrates, the blood also carries out complex functions of transport, homeostasis and defense.”

6

So… screw cloning red blood cells, why not just clone bone marrow in a scaffold of sorts and bathe it in the proper nutrients until it starts cranking out red blood cells.

–Tim

7

Blood evolution is actually pretty clearly spelt out in biology, if you know where to look.

Very primitive organisms were, and are, small enough that they don’t need blood - stuff can diffuse in and out all on its own.

Moving up the ladder, we come to, oh, let’s say sponges. Sponges are very large structures, compared to the distance stuff can diffuse, but they’re riddled with channels. Any given cell in the sponge is within diffusion distance of a nearby channel of water.

It’s really not hard to see how a sponge-like organism could come up with some proteins it could secrete into its channels to make the process more efficient, thus allowing it to reduce the channel size, and, eventually, closing them off completely as its fluids became specialized enough.

Coming at it from the other end, humans have several nonfunctional copies of genes related to hemoglobin - evolutionary leftovers. Going back further, you find animals that use myoglobin rather than hemoglobin - hemoglobin basically consisting of 4 attached myoglobin-like molecules. (I can’t remember off the top of my head where the myoglobin/hemoglobin cutoff is, evolutionarily) Hemoglobin, incidentally, is far more efficient than myoglobin, because the subunits cooperatively increase oxygen and CO[sub]2[/sub] binding rates. Anyway.

Finally, primitive circulatory systems, like in insects, don’t have blood vessels or anything of that type. Take the grasshopper as an example (I’m thinking back a few years to remember this, so forgive me if I’m not right on). It basically has a tube running down its back and one down its ventral side. Blood (well, not really blood - their version) comes out of the top tube, runs down over all the organs, including the respiratory ones, and pools in the bottom, where it’s pumped back to the top.

So, yeah, the existence of blood doesn’t overturn evolution or anytihng.

8

Rats. Perfectly good post screwed up with a typo in the last word. Figures.

9

If you can figure out a way, you will have the Nobel Prize. Currently we can only harvest stem cells from human fetuses. That obviously has some problems.

Smeghead, very good discussion on hemoglobin (which, by the way cmkeller, is only in the erythrocytes). Love the sig.
-Beeblebrox
42!

10

Actually, Homer, Beeblebrox, there are cases - certain leukemias, for instance - where they extract specifically the blood precursor cells from the bone marrow, grow them up, and reinject them to fight the side effects of chemotherapy. Eh. Bad sentence. Let me rephrase. Chemo tends to kill rapidly-dividing cells, like blood cells. So before they start chemo, they’ll extract a goodly amount of blood cell precursors from the bone marrow and grow them in culture. Then, when chemo has depleted these cells, they can reinject them, and since they’re from the same person, there’s no rejection problem.

The problem with doing this commercially is that even these precursors are only viable for a couple of dozen divisions. In other words, there’s a limited time span when they’ll keep growing. They die in culture fairly quickly. I suppose you could immortalize them, like they do with lab cultures, but that introduces more problems.

So the problem isn’t getting the stem cells - we can do that without needing fetuses - but keeping them alive long enough to make the idea viable.

11
12

Damn good point. Do you want to donate bone marrow, though? The procedure lays you out for a couple of weeks. If you are a cancer patient, however, it’s better than the alternative (i.e. death).

Also, as I understand, the extracted cells are not true stem cells (stem cells can develop into anything - liver cells, neurons, whatever). They have already differentiated, but they will still make blood cells. My saying “stem cells” earlier might have been a misnomer.

One thing. I have done plenty of cell cultures but never heard the term “immortalize”. What do you mean?

13

Yeah. I think we’re on the same page, really.

Immortalized cell lines have been hybridized with cancer cells. One of the characteristics of cancer cells is that they grow more than normal cells. Ideally, the hybrid cells should retain all of the characteristics of the original cells, plus the ability to grow abnormally, though it’s not always that simple.

14

I’m not a biologist, but I thought they could now immortalize cells by adding telomerase rather than mixing them with cancer cells. My understanding is that cancer cells are immortal because, like stem cells, they have the gene for telomerase activated, unlike ordinary cells which have it deactivated.

15

There’s usually more than one change required for a cell to become immortalized. Telomerase is an important and very active area of research, but it’s only one piece of the puzzle.

16

So…

Can anyone tell me why research groups aren’t paying for women’s hospital and birthing costs in exchange for the rights to the stem cells which are found in the cord blood and placenta? Why the hell aren’t these research groups exchanging hospital and birthing costs for the much-wanted and much-needed stem cells?

Can you imagine how much easier life would be for women if instead of having to have insurance kick them in their sewn-up junk after having a kid, they walked (or rolled) into the hospital, signed a waiver, and had it all taken care of by a research group? They show up with a bloated gut and leave with a kid and no expenses.

–Tim

17

Cord blood is routinely harvested and researched. A last ditch option for children needing a bone marrow transplant is for the parents to have another kid – nowadays, embryo selection has even been used to select the HLA matching sibling. Even before birth I believe cord blood can be harvested and used for a bone marrow transplant.

Stem cells are routinely cultured and forced to differentiate by addition of certain growth factors to the media. Bone marrow stem cells have been made to differentiate into other things – at my school, they can make primitive muscle cells from bone marrow and blood cells from the satellite stem cells in muscle. Recently, IIRC, neuronal cells have been made from satellite cells. The stem cell picture is quite unclear at present and rapidly changing. Also, a bone marrow donation won’t lay you out for a couple of weeks – maybe a day or so, IIRC from medical school.

I’ll also add that Jose Carreras had an autologous bone marrow transplant when he had leukemia. It involves whole body irradiation to kill off all of the bone marrow and then transplantation with carefully washed bone marrow which you bank before. All blood cells (including the cancerous leukemiac ones) are killed in the irradiation, and after transplantation all blood cells should be derived from the carefully washed banked ones. IIRC it is still quite an experimental therapy, fraught with complications as you become severely immunosuppressed while waiting for the new bone marrow to grow.

To the OP: The heart and blood are organs which are very highly developed for a certain purpose. As Smeghead pointed out, we are surrounded by numerous examples of different paths taken to provide a similar function. Insects have a hemolymph, crustaceans use a copper-based oxygen transport scheme. Hearts come in all shapes and sizes, from simple pulsating tubes to the highly folded and complex mammalian heart. Blood vessels are also highly varied. Even the phloem of plants can be thought of a similar means to an end.