American schoolchildren often begin their study of U. I distinctly remember a story we were told about how sailors eventually learned to carry potatoes or limes on their long voyages in order to prevent the what animals cannot make vitamin c called scurvy. We now know that scurvy is caused by a deficiency in ascorbic acid, also known as vitamin C. Without it, we cannot make collagen and our tissues lose integrity, bones become brittle, we bleed out of various orifices, and our bodies basically fall apart.
However, have you noticed that neither dog food nor cat food contains any citrus fruit? Both dogs and cats can get by on meat and rice, with no vitamin C whatsoever, and they never develop scurvy. How do they do it?
They make their own vitamin C. In fact, what animals cannot make vitamin c, the cells of nearly all animals on the planet make plenty of their own vitamin C and thus have no need for it in their diets. Humans and other primates are pretty unique in our need to have vitamin C in our diet. This is an example where our ancestors clearly had more functionality than we have now.
Somewhere in our lineage, we actually lost the ability to make vitamin C. How did we lose it? We have the gene, but it has been mutated to the point of being nonfunctionalmaking it a so-called pseudogene.
Somewhere in the ancestor of primates, the gene suffered a mutation, rendering it inoperable, and then random mutation continued, littering the gene with tiny errors. We can still easily recognize the gene. You can easily see that it is still a car, what animals cannot make vitamin c. In fact, you would have to look very carefully to see that anything was wrong at all. But yet, it cannot function as a car, even slightly. The spark plug was removed by a random mutation.
Random mutations happen all the time. Often, they are of no consequence, but sometimes they occur right smack in a gene. When that happens, it is almost always bad because the mutation disrupts the functioning of the gene. The individuals suffering this mutation are then a little worse off or a lot worse off and harmful mutations are eventually eliminated from the population. This begs the question: The consequences of this mutation ought to have been quick and harsh.
What if this disrupting mutation happened to a population of mammals that already had lots of vitamin C in their diet anyway?
There would be no consequence of losing the ability to make vitamin C, if they were already eating foods that contain it. What foods contain a lot of vitamin C? And where do citrus fruits mostly grow? And where do most primates live?
Since that time, primates have pretty much stuck to the rainforests and their inability to make vitamin C might be part of why that is. A few other animals have this also. Not surprisingly, the ones that tolerate having a broken GULO genes are ones what animals cannot make vitamin c get plenty of vitamin C in their diet.
Take fruit batsfor example. They eat, um, fruit. Interestingly, our bodies, like those of other animals that have lost the ability to make vitamin C, what animals cannot make vitamin c, have attempted to compensate by increasing our dietary absorption of it. Our inability to make vitamin C puts strict constraints on our diet, upon pain of disease and death. Our broken GULO gene is an example of how the human body, though intricate, efficient, and beautiful, is definitely not perfect.
There are a few design flaws under the hood. Nathan, I was reading your spot on vitamin C and saw your response to the bacterial flagellum argument.
I find this interesting because the community thinks this problem was solved by Judge Jones ruling in Dover, PA. Somehow Ken Miller and others gave the impression that the evidence must have been presented that showed a detailed evolutionary account of this organelle. But in a flagellum review article published by Academic Press in four years after the Dover TrialS. Aswawa has this quote:. If the flagellum has evolved from a primitive form, where are the remnants of its ancestors?
How was it possible that the flagella have evolved without leaving traces in history? So one of the preeminent scientist working on this structure contradicts the consensus. To be fair, both Aizawa and Kelly Hughes have made Salmonella flagellar gene knockouts and found compensatory mutations that restored motility in one or two genes in attempts to refute irreducible complexity but this is a far cry from demonstrating an evolutionary pathway.
But I agree it is a beautiful molecular design. If we discover a long lost prokaryotic clade, that may help clarify how it evolved. Actually, we have a pretty good idea of how the erythromycin animal evolved. Reblogged this on pankeahomtfy. Could ancestral primates also have gotten sufficient vitamin C from diets high in leaves, what animals cannot make vitamin c, which I understand contain some vitamin C as well?
As early humans left Africa in waves, how did they get enough vitamin C when they got to higher latitudes? Vegetables or other fruits must have been vital to their diets, or could they have gotten vitamin C from a high-meat diet?
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