bleistift2@sopuli.xyz
on 10 Jan 2025 21:53
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Damn, this got long. A while back, I read “Only a trillion”, a collection of science essays by Dr Isaac Asimov (yes, the Isaac Asimov; he was professor in biochemistry). I found it mind-blowing how animals evolved out of water and back, and by what traces we can infer that. So here’s a longish excerpt from chapter 9 of that book.
Consider the manner in which life-forms moved out of the sea […] into fresh water and onto land. That involved not only the familiar morphological evolution, but biochemical evolution as well. In the sea, cells developed in a liquid containing certain ions […] in certain concentrations.
Life made the adjustment to those concentrations once and apparently that was it for all time.
When animals grew more complicated and became a group of cells enclosed in some form of shell, skin, protective membrane or what have you, the individual cells remained immersed in an inner liquid resembling sea water in ionic composition. The outer portions of the body, as well as many other things, changed to suit altered conditional liquid, the liquid with which the cells were in actual contact, remained about the same. Our own blood […] is remarkably like a quantity of trapped sea water, and so is the interstitial fluid that exists in the spaces between our cells.
In other words, we’ve never left the sea; we’ve taken it with us.
[…]
Primitive sea creatures have no trouble maintaining the ionic composition of their internal fluids because it is mostly in even balance with sea water, and they have learned, with the millions of years, to tolerate slight changes that may develop in sea water and hence in their own fluids. But when a sea creature invades the fresh water (which, biochemically, is as difficult a feat as the invasion of land) a completely new situation develops.
When a sea creature tries to live in fresh water, it must somehow counteract the natural tendency of the ions within itself to leak out […].
It is considered that any creature that can keep a surplus of ions inside its body against a deficiency on the outside must have had some ancestor that adapted itself to fresh-water. All vertebrates apparently come into this classification and so it is deduced biochemically that the original vertebrate from which all others are descended developed in fresh-water.
To be sure, a number of fresh-water vertebrates migrated back to the sea, to become the ancestors of the marine fish and […] sharks […]. They had the reverse problem now; to keep surplus ions from entering […].
You can find details […] in an excellent little book by Ernest Baldwin called Comparative Biochemistry, published by the Cambridge University Press in 1948.
The conquest of the dry land involved a whole new series of biochemical modifications. One of these concerned the matter of waste-disposal.
[…]
Now for any creature living in fresh water, there is no problem. Carbon dioxide and ammonia are soluble in water, and water is just water. Dump all three substances into the river.
[…]
In fact the only suspicion of risk involves ammonia which is highly poisonous. One part in 20,000 in blood is enough to kill.
[…]
The sharks […], after migrating from their fresh-water origin back to the sea, were faced with keeping ions from the ocean surplus from invading their body. Instead of developing ion-excreting mechanisms as the marine fish did, they worked out the trick of breaking down nitrogen compounds to urea instead of ammonia. Then they allowed urea to concentrate in the blood as they could never have done with ammonia.
In fact they allowed urea to accumulate to a concentration of 2 per cent, which is enough to kill other creatures. Through the ages, shark tissue acclimated itself to urea. The urea in the blood acted as the ions did, in a way, and made the total ion content of shark blood higher than that of the ocean. The problem was therefore once again to keep the ions from leaking out and the sharks could use their old fresh-water adaptations for the purpose instead of having to invent new mechanisms, as the sea fish did.
Incidentally, some sharks migrated back to fresh water after having developed the urea-waste mechanism. Once in fresh water, the presence of urea in the blood was not only unnecessary, it was down right embarrassing. It made the ion content of the blood artificially high so that it was harder than ever to keep it steady against the ion-free fresh water. The fresh-water sharks did the best they could by cutting down the urea concentration in blood from 2 percent to 0.6 per cent, but there they reached their limit. Shark tissue had grown so accustomed to urea, it had become positively dependent upon it. Shark heart, for instance, won’t beat in blood containing no urea. (Our hearts would do fine.)
[…]
A
The_Che_Banana@beehaw.org
on 10 Jan 2025 22:13
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bleistift2@sopuli.xyz
on 11 Jan 2025 17:28
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Thank you!
fossilesque@mander.xyz
on 11 Jan 2025 18:06
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😎
LordTrychon@startrek.website
on 11 Jan 2025 10:27
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Isaac Asimov is considered one of the greats of 20th century science fiction. Again, while most famous for writing science fiction he wrote much more than just that.
Isaac Asimov has won scores of Hugo Awards for stories and for Best Editor; dozens of Nebula Awards; several World Fantasy Awards; over a dozen Theodore Sturgeon Awards and Homer Awards; and multiple Sidewise Awards1. He has won Hugo Awards for Best Related Work, Best Novelette, and Best Editor.
cyrano@lemmy.dbzer0.com
on 10 Jan 2025 22:27
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Thanks for sharing
Bademantel@lemmy.world
on 11 Jan 2025 06:28
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Absolutely fascinating! Now I have a new entry at the top of my list of books that I need.
bleistift2@sopuli.xyz
on 11 Jan 2025 09:54
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Be advised that the book isn’t all about evolution or even biology.
Bademantel@lemmy.world
on 11 Jan 2025 14:16
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Thanks for the heads-up. I looked into it and I’m very interested. I ordered the new print because there are not many used versions around.
bleistift2@sopuli.xyz
on 11 Jan 2025 14:27
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Have fun, but beware of the rabbit hole that is Asimov’s life work.
flora_explora@beehaw.org
on 12 Jan 2025 11:48
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Very interesting indeed! It’s fascinating how many adaptations there are that aren’t as obvious as anatomical ones.
Although I would take the validity of this excerpt with a grain of salt. The evolution of different kinds of fish is really messy (as they are a paraphyletic group anyways). I couldn’t find any info on how any fish or sharks evolved in freshwater conditions for example (just that their urea content is indeed higher). If you have any info on that, I would be glad to read it :)
The only interesting bit I did find was this pbs eons episode on how armored fish evolved to probably store minerals like calcium and potassium and how other vertebrates today use their endoskeleton to store those same minerals.
bleistift2@sopuli.xyz
on 12 Jan 2025 13:05
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I would take the validity of this excerpt with a grain of salt
Indeed. The quote was first published in 1957 and may be heavily outdated. I cannot judge for myself, because I know next to nothing about biology, but Asimov’s astronomical essays are plain wrong by today’s knowledge.
Also keep in mind that this was written for science fiction readers. So there are necessarily simplifications that may not survive close scrutiny (again: I’m not an expert here).
flora_explora@beehaw.org
on 12 Jan 2025 21:32
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Ah OK, thanks for the context :)
jabathekek@sopuli.xyz
on 10 Jan 2025 22:14
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It’s free real-estate.
satans_methpipe@lemmy.world
on 11 Jan 2025 08:54
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I’m only upvoting as a means of pointing at the gif of the same comment above your comment in my feed.
marduk@lemmy.sdf.org
on 10 Jan 2025 22:22
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Ha, and Scientists actually want us to Believe this‽
OutlierBlue@lemmy.ca
on 11 Jan 2025 00:35
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No, they want you to look at the evidence and understand that it happened.
marduk@lemmy.sdf.org
on 12 Jan 2025 06:13
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I have considered the evidence
CeruleanRuin@lemmings.world
on 12 Jan 2025 13:48
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Have you indeed?
marduk@lemmy.sdf.org
on 13 Jan 2025 00:13
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Indeed I have
chuckleslord@lemmy.world
on 11 Jan 2025 04:33
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They don’t ask you to believe anything. This is what the evidence points to, it doesn’t require belief at all.
angrystego@lemmy.world
on 11 Jan 2025 08:01
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They played us for absolute fools.
marduk@lemmy.sdf.org
on 12 Jan 2025 06:15
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“They went back into the water” - statements dreamed up by the utterly Deranged
troyunrau@lemmy.ca
on 10 Jan 2025 23:12
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Land whale. My new favourite phrase
GJdan@programming.dev
on 10 Jan 2025 23:38
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Isn’t that just what you call OP’s mom?
jabathekek@sopuli.xyz
on 11 Jan 2025 17:59
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OOOOOOOHHHHHHHHHHHHH!!!
ryedaft@sh.itjust.works
on 10 Jan 2025 23:47
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And nobody has echo location
OutlierBlue@lemmy.ca
on 11 Jan 2025 00:34
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ryedaft@sh.itjust.works
on 11 Jan 2025 09:58
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Yep, we know. Mammalian ears are so advanced that echolocation can be enabled without extra evolution. This allowed mammals to enter both the seas and the sky - ecological niches where there was already a lot of competition and predators.
threaded - newest
<img alt="" src="https://lemmy.world/pictrs/image/7f5bee02-502f-4764-88f3-acf4f40b168f.gif">
This version is unsettingly high quality
idk why, but I only see a blank comment ;-;
<img alt="" src="https://sopuli.xyz/api/v3/image/7f5bee02-502f-4764-88f3-acf4f40b168f.gif">
It’s still not working :S
Damn, this got long. A while back, I read “Only a trillion”, a collection of science essays by Dr Isaac Asimov (yes, the Isaac Asimov; he was professor in biochemistry). I found it mind-blowing how animals evolved out of water and back, and by what traces we can infer that. So here’s a longish excerpt from chapter 9 of that book.
Very, very much enjoyed reading this
I didn’t want it to end
Then I have good news! Isaac Asimov published 357 books during his lifetime, and edited/annotated many more. You can keep reading for years!
en.wikipedia.org/…/Isaac_Asimov_bibliography_(chr…
See…now that just sounds like homework :(
He wrote 40 novels and a lot of short stories, and is a great read almost always. He also wrote textbooks because he was just amazing.
Well don’t stop now that I’m getting all excited about him
Hunting for his books is a bitch, though.
www.vialibri.net
Thank you!
😎
Isaac Asimov is considered one of the greats of 20th century science fiction. Again, while most famous for writing science fiction he wrote much more than just that.
Isaac Asimov has won scores of Hugo Awards for stories and for Best Editor; dozens of Nebula Awards; several World Fantasy Awards; over a dozen Theodore Sturgeon Awards and Homer Awards; and multiple Sidewise Awards1. He has won Hugo Awards for Best Related Work, Best Novelette, and Best Editor.
Thanks for sharing
Absolutely fascinating! Now I have a new entry at the top of my list of books that I need.
Be advised that the book isn’t all about evolution or even biology.
Thanks for the heads-up. I looked into it and I’m very interested. I ordered the new print because there are not many used versions around.
Have fun, but beware of the rabbit hole that is Asimov’s life work.
<img alt="" src="https://sopuli.xyz/pictrs/image/71406bf0-46f0-4d63-a328-dd2b79a503d8.webp">
(In no way complete)
Very interesting indeed! It’s fascinating how many adaptations there are that aren’t as obvious as anatomical ones.
Although I would take the validity of this excerpt with a grain of salt. The evolution of different kinds of fish is really messy (as they are a paraphyletic group anyways). I couldn’t find any info on how any fish or sharks evolved in freshwater conditions for example (just that their urea content is indeed higher). If you have any info on that, I would be glad to read it :)
The only interesting bit I did find was this pbs eons episode on how armored fish evolved to probably store minerals like calcium and potassium and how other vertebrates today use their endoskeleton to store those same minerals.
Indeed. The quote was first published in 1957 and may be heavily outdated. I cannot judge for myself, because I know next to nothing about biology, but Asimov’s astronomical essays are plain wrong by today’s knowledge.
Also keep in mind that this was written for science fiction readers. So there are necessarily simplifications that may not survive close scrutiny (again: I’m not an expert here).
Ah OK, thanks for the context :)
It’s free real-estate.
I’m only upvoting as a means of pointing at the gif of the same comment above your comment in my feed.
Ha, and Scientists actually want us to Believe this‽
No, they want you to look at the evidence and understand that it happened.
I have considered the evidence
Have you indeed?
Indeed I have
They don’t ask you to believe anything. This is what the evidence points to, it doesn’t require belief at all.
They played us for absolute fools.
“They went back into the water” - statements dreamed up by the utterly Deranged
Land whale. My new favourite phrase
Isn’t that just what you call OP’s mom?
OOOOOOOHHHHHHHHHHHHH!!!
And nobody has echo location
en.wikipedia.org/wiki/Human_echolocation
Yep, we know. Mammalian ears are so advanced that echolocation can be enabled without extra evolution. This allowed mammals to enter both the seas and the sky - ecological niches where there was already a lot of competition and predators.