My response to the toothache thread.

This is one of those question/topics which isn't super easily explained and can be misinterpreted. So immunity doesn't change and grow down the bloodlines if a particular pathogen is present, a person immunity is cultivated during their lifetime by constant exposure to pathogens and the random generation of antigen receptors on immune cells. This is not to be confused with genetic mutation which can help mitigate the effects of certain illness like sickle cell anemia in regards to malaria.

I'm sure our more sugar heavy diets have played a significant role in our health but even if you didn't eat a more western diet you'd still be in danger of infection either way. We also don't know if our ancestor's suffered from tooth problems either as teeth do tend to go missing from skeletal remains and the teeth we do find can still harbor the evidence for bacterial infection but we can't be 100% certain that bacteria originated from the tooth or if the infection was systemic in nature.

Anyways, take home message is our immune systems don't evolve to fight a particular pathogen even if it's present in our environment over generations. If this were true we wouldn't have need a vaccine to beat smallpox or any of the really old diseases.

Since you brought up the subject of evolution, I found this interesting. It appears species evolution can occur in as little as 2 generations through natural hybridization and that evolution through mutations over time is not the only way for species differentiation.

https://sciencealert.com/darwin-s-f...pecies-in-real-time-two-generations-galapagos

So it's a bit strange you bring that up. I read through the article you posted and went to the link provided to the journal Science. My university gives me access to the journal so I wanted to read the author's report and skim through their sequencing data but the link to the full article is dead and it's not listed in the table of content. I wonder if someone has already spotted something a miss in their findings and the article was pull due to it.

Barfus said:

So it's a bit strange you bring that up. I read through the article you posted and went to the link provided to the journal Science. My university gives me access to the journal so I wanted to read the author's report and skim through their sequencing data but the link to the full article is dead and it's not listed in the table of content. I wonder if someone has already spotted something a miss in their findings and the article was pull due to it.

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It hasn't been pulled. I've got it open in front of me.

Abscessed teeth don't always result from cavities. Sometimes they can happen because of trauma to the nerve (which dies) from an impact or chronic pressure, such as from tooth clenching or grinding, or from tooth wear, or from cracking of a tooth from biting something that's too hard.

I've had an abscessed tooth, and I can honestly say it's the worst pain of the chronic sort I've ever experienced. Vicodin barely put a dent in it. The five days I had to wait before they could get me in for the root canal were the longest of my life. I quite literally feel your pain and am glad you are feeling better now.

One thing to consider is that tooth problems in prehistoric times were more common in older people, whose teeth had worn down by then (food was much more abrasive back then). Once you're middle aged or old, you've already passed on your genes, most likely, so genetic differences in tooth aging may not be a strongly selected thing.

Though there is the so-called grandmother hypothesis, which is the proposal that human longevity evolved because elders (especially mothers) increased their grandchildren's fitness by helping their children raise them, so who knows. People could actually live a pretty long time in prehistoric societies (some anthropologists hypothesize that average lifespans actually went down once people settled down and became more reliant on agriculture).

Still, people died of things we can treat now. I think pulling teeth goes back a long way, though. I imagine it was harder to get the whole tooth, root and all, out before anesthetics and sophisticated tools, though.

As you noted, people didn't have access to processed sugar much before the early modern era, so back in the old, old days the only really sticky sweet was honey. Though I read an article in Natural History some years ago that stated the widespread consumption of cooked cereal products did cause an increase in tooth decay (as opposed to tooth wear) after pottery was invented.

Re evolution, every trait will show a certain amount of variability. In prehistoric (and pre-industrial) times, if an abscessed tooth couldn't be pulled or the gum lanced and the infection drained or burned out from below, its owner likely died. People (and other animals) have been dying prematurely of various things throughout the history of life. Natural selection can't build perfect, immortal bodies. It can only select among the best of what's available at the time. And what's best is often a matter of tradeoffs and will vary (and change) with the environment.

In the wild, many mammals die when their teeth wear out, but nature can't make indestructible teeth, and mammals seem to have traded teeth that can grow back continuously (as seen in fish and reptiles) throughout their lives for teeth that are more deeply socketed in the jawbones and differentiated into different tooth types (which are adaptations to needing to chew their food).

So tooth wear and decay is one of those trade-offs mammals have to deal with.

Seaclusion said:

Since you brought up the subject of evolution, I found this interesting. It appears species evolution can occur in as little as 2 generations through natural hybridization and that evolution through mutations over time is not the only way for species differentiation.

https://sciencealert.com/darwin-s-f...pecies-in-real-time-two-generations-galapagos

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I just read that article yesterday. Pretty interesting. This kind of speciation, caused by hybridization where the hybrids can only breed with each other, is well documented in plants (modern domestic wheat resulted from a hybrid), but as far as I know (tell me if I'm wrong, Helix) it hasn't been seen as often in animals, especially vertebrates.

Though hasn't hybridization been responsible for some of those all-female species of lizard that reproduce by parthenogenesis? Presumably this would have happened in just two generations also.

You're right, Roxxsmom, it's definitely not commonly recorded in vertebrates. Prob the most well-known hybrid species among the verts is Heteronotia binoei, a parthenogenetic gecko widespread in inland Australia.

Hetero it's not.

I was trying to find out what -notia meant, but Google kept suggesting I really wanted to look for naughty. I didn't want to risk it, so gave up.

(Related to the not- in notochord maybe?)

Helix said:

It hasn't been pulled. I've got it open in front of me.

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Yeah, I don't know why the article wouldn't load last night but I finally got a chance to read it. It's a super interesting read, I'll be curious to see if the Big Bird lineage will be able to survive much longer due to its low population size and genetic homogeneity between mating pairs. I also will find it interesting if they are able to check in the lineage can successfully mate with G. conirostris on Española.

Helix said:

You're right, Roxxsmom, it's definitely not commonly recorded in vertebrates. Prob the most well-known hybrid species among the verts is Heteronotia binoei, a parthenogenetic gecko widespread in inland Australia.

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Yep, and some of the unrelated whiptail lizards of the American southwest.

Albedo said:

Hetero it's not.

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Nor are the southwestern lizard "ladies."

There were some papers many years ago that had pictures of female whiptail lizards in coitus--possibly required to stimulate ovulation of the eggs that develops photogenically into a clone of their mother.

http://www.pnas.org/content/77/1/499.full.pdf

Here's a more recent article on these lizards, which are apparently tetraploid (also much more common in plants than in vertebrate animals).

https://www.scientificamerican.com/article/asexual-lizards/

Okay, what was this thread about again? Oh yeah, teeth.

Random thoughts from my overfilled brain:

Seaclusion said:

Since you brought up the subject of evolution, I found this interesting. It appears species evolution can occur in as little as 2 generations through natural hybridization and that evolution through mutations over time is not the only way for species differentiation.

https://sciencealert.com/darwin-s-f...pecies-in-real-time-two-generations-galapagos

Click to expand...

That article is about bird evolution, not human evolution. Microorganisms can evolve in hours, humans, not so much.

When human genomes were looked at across the globe it was found we are all one species. There are no sub-species even with groups like the Australian Aboriginals which before Europeans come to Australia were isolated for 60K years give or take a dozen K. That doesn't mean adaptations can't arise within a species, they can. But one has to be careful in how one conceptualizes human evolution.

Some examples: dark skin evolved more than once as humans migrated north from Africa with skin getting lighter over thousands of years, then getting darker again as humans migrated south down the American continents toward the equator. Light skinned Europeans in Australia will have to wear hats and sunscreen for many generations to come, we're good at adapting until that very slow evolution makes its corrections.


As for the pathogen-human arms race, remember the little buggers are also evolving. Our best successes against tooth decay before modern medicine actually came from passing on colonies of good bacteria to the next generation. People with certain normal oral flora have more resistance to cavities than people with less protective normal flora.

Human fossils include people who have suffered horrible abscesses and tooth decay. If the tooth didn't fall out infection can spread into to bone, and it does. Other ancient people have surprisingly good teeth, the luck of the draw.


Mummy with Mouthful of Cavities Discovered

Rather than age, he may have succumbed to a sinus infection caused by a mouthful of cavities and other tooth ailments, according to new research on the man's odd dental filling.

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Otzi the Iceman had bad teeth.

Bad teeth in ancient Egyptians

Worn teeth, periodontal diseases, abscesses and cavities tormented the ancient Egyptians, according to the first systematic review of all studies performed on Egyptian mummies in the past 30 years.

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These Newly Discovered Bacteria Can Help Prevent Cavities, And Scientists Want to Put Them in a Pill


As for smallpox, Wiki has a good article on the virus.

The overall case-fatality rate for ordinary-type smallpox is about 30 percent, but varies by pock distribution: ordinary type-confluent is fatal about 50–75 percent of the time, ordinary-type semi-confluent about 25–50 percent of the time, in cases where the rash is discrete the case-fatality rate is less than 10 percent. The overall fatality rate for children younger than 1 year of age is 40–50 percent. Hemorrhagic and flat types have the highest fatality rates. The fatality rate for flat-type is 90 percent or greater and nearly 100 percent is observed in cases of hemorrhagic smallpox. The case-fatality rate for variola minor is 1 percent or less.[23] There is no evidence of chronic or recurrent infection with variola virus.[23]

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If pathogens are too efficient at killing the host, they will soon run out of hosts.

Organisms like highly pathogenic influenza at first spread rapidly in a population. But they rapidly become attenuated as the most lethal strains die out with the host, while the less deadly strains reproduce more readily. Eventually milder and milder strains are selected and the pandemic subsides until the next highly pathogenic strain emerges.