Tune in today (February 16, 2020) at 3pm CST to watch @NLents and @swamidass debate whether life is badly designed or not.
2 Likes
Will it be recorded for later viewing?
1 Like
Yes, at the same link!
1 Like
Looking forward to watching it tonight. We are talking about this in one of my classes right now.
1 Like
Great conversation @nlents. You did atheists proud. 
Thanks. I didn’t think so, actually, but I’ll watch the tape and see. It was definitely a fun conversation, though!
1 Like
@nlents what do you think of this paper?
My uni doesn’t subscribe to that journal, so I can’t get the full-text. Send me a PDF? I have to ay that I’m pretty skeptical based on the abstract. These rats were made vitC-deficient transgenically and yet they saw an immediate behavioral response kick in? With no history of such a response being needed or appropriate? Cmon. I need to see these data.
1 Like
It points to either behavior or a hardwire system that can do this generically for vitamins/nutrients, perhaps by pairing foods with how it affects health in plastic system.
Remember also they have much better sense of smell than us. So it also could be explained by smelling the vitamin C.
So that is two hypothesis that would explain this. I’d have to look it up where this was explored, but the fact that olfaction is so tied into the amygdala was offered as support for this idea, if I recall. A sort of hard wired and subconscious memory that emphasizes food. It is easy to see how that would be adaptive.
Now, I’m a bit skeptical of this specific paper too. It doesn’t look like it was cited by any one. But there is actually quite a bit of work done on specific hunger, and how it interacts with vitamin deficiency.
Not in animals with no history of requiring dietary vitamin C. Are the authors suggesting this instinct was just there waiting for the possibility that their GULO gene may one day be mutated? Cmon.
That’s really interesting, but I hope it’s more solid than the flight of fancy that this paper seems to be based on.
I read the paper, and it seems that the vitamin C-containing water was obviously more acidic (citric acid), and the vitamin C-deficient rats preferred more acidic water even when they used other acids. It seems to me that the vitamin C-deficient rats had a preference for more acidic water because of the association between low pH and vitamin C content, but There’s nothing to suggest the association goes any deeper than pH.
Unfortunately the authors didn’t do an experiment where they tested to see if the rats preferred vitamin C-containing water or water of the same acidity without vitamin C.
1 Like
Well that is my summary of a hypothesis I heard elsewhere, and it is more grounded than merely my comment.
More interesting though, do you know if any animals or animal remains that show signs of scurvy in a natural context?
Also, outside of long sea voyages which limit access to food choices, do you know of examples of scurvy in humans?
I though the VitC- mice had a stronger preference than WT. If that is the case, and it is good data, this does suggest something more than merely pH.
Scurvy was documented as far back as ancient Egypt: First probable case of scurvy in ancient Egypt at Nag el-Qarmila, Aswan - ScienceDirect
(And some good references in there.)
According to The WHO, scurvy is major health risk among refugees: https://www.unhcr.org/4cbef0599.pdf
Because of supplementation, the availability of natural sources, and the fact that you don’t really need much vitC, scurvy is pretty rare in the developed world, but it still exists: Scurvy Is Still Present in Developed Countries
1 Like
I don’t doubt that appetites/cravings for specific micronutrients can and have evolved. I do seriously doubt that they could emerge in a single generation in an otherwise GULO-capable species like rats.
1 Like
I don’t know of any, but you are asking for an exceedingly rare find. All extant supraprimates are the product of hundreds of millions of years of acquiring vitC in their diet, so they have overcome the defective GULO gene through behavioral adaptations. But animals are always exploring, expanding, trying out new habitats, lifestyles, foods, etc. The point here is that the boundaries of where primates can thrive are set by, among other things, availability of vitC in the environment. Before hominins, primates never successfully colonized Europe, but I think we can say with great certainty that it’s not because none ever tried. In fact, there is now a population of Barbary macaques in Southern Spain, having arrived as stowaways on boats arriving from Morocco. They are thriving because the Spain of today has plenty of vitC to be found from human human food waste, farming, etc. I think it sort of proves the point that, as soon as wild primates COULD thrive in Europe, they now are.
1 Like
They have a stronger preference for water containing vitamin C (which was acidic), and also a stronger preference for acidic water that contained other acids. From this data it’s impossible to conclude that their preference was somehow specific to vitamin C, in fact it shows the opposite - that they have a general preference for acidic water.
2 Likes
Ah I see. Thanks @evograd.
@nlents thanks for your response. I don’t want to muddy the water here with any more speculation. When I get a chance, I’ll look into a literature search and report back what I find if it is helpful
What drove this for me, to be clear, is curiosity. It is very possible you are right. Perhaps I just need to be educated.
1 Like