I think people in HN (and in general) have to remember the central axes of evolution before digesting this kind of article. I've already seen comments like it's "odd that no species has ended up evolving a continuous maintenance system" and "sleep has a higher opportunity cost in humans" in this comments section.
This is a common, but poor framing of evolution. Remember: the only real rule with evolution is "did this evolutionary change mean they survived / reproduced more"? Evolution is not a local or global maxima solving function. I find this kind of attempt at interpreting selection common with engineers, programmers, etc.
Did their genes survive more, you mean. Hyper-vigilance could be maladaptive for the individual and still survive if it benefits others that carry the gene for it.
A bit of a digression, but I recently learned about the concept of pangenomes, of trying to map not just the genes in one individual, but the entire set of genes from a clade. It seems it matters a lot in practice for e.g. the immune system that we don't all have the same surface proteins on our cells, even if done some surface proteins are clearly better than others.
I'm a biologist so forgive me the poor wording, but there are "infinitely high" peaks/walls in the evolutionary landscape, as in: "the human urinary system has some evolutionary constraints and anatomical features that are not optimally designed from an engineering perspective, but they are generally functional and reflect our evolutionary history rather than deliberate design." <- this is from AI, I didn't remember the details, but the ureters or urethra take a long way around the inner part of the body because at some point it was a good route, but as we evolved it became suboptimal, but we can't just evolve to untangle all the pipes in our body and do some cable management... We're stuck with what we have (no tunneling electrons ;)).
So in that sense, a global maxima (minima?) solving function will probably not arrive at what we have, it has to take into account our evolutionary path, in its entirety (as in the whole tree.), because it is all encoded in 1 (or several) long molecules, and a radical changes would take a rewrite of many parts at the same time, which just does not happen. Maybe at some point we can do it ourselves... though I imagine there being a lot of unintended consequences in other places in the body :).
Another example is that sometimes complexity in a cell signalling cascade is simply there to get some timing right (ie delay some response), and the complexity is just there, and won't simplify by itself -> But then later the complexity may start to serve some purpose. Just like proteins that are "copypasta-ed" in the genome, leaving one copy free to mutate and attain a function, or not... etc etc.
That is the difference between global and local optima.
We're not at a local optimum though, our bodies can probably evolve to produce half the urine or something without changing the route, but there is no evolutionary pressure to do so.
Yes, but we cannot evolve to have our urinary tracts take a more efficient route (or at least the probability is exceedingly low), even though there would be pressure to do so. (Maybe I'm misunderstanding your point)
I did not know human urinary tract was suboptimal.
Are there examples of "discontinuous" evolution where a chance mutation stumbled upon a much better way to do something that allowed a species to jump the gap?
I imagine it would be very rare because chance mutations in a single individual that confer extraordinary survival / mating advantage to offset entire population would be rare like being a superman among men.
"I imagine it would be very rare because chance mutations in a single individual that confer extraordinary survival / mating advantage to offset entire population would be rare like being a superman among men."
-> This also depends on population size, if there is a bottleneck event (ie 99.99 percent of some species dying) then among the 100's of survivors perhaps there could be a superman. Either because this person got lucky, or the rest got unlucky. But in general the distribution of traits is quite continuous, given large populations.
It's also good to keep in mind that us biologists have messy definitions, ie we call specimen A and B the same species when they produce fertile offspring. Some species produce offspring but infertile (Horse-Donkey, Lion-Tiger). But what if A and B have fertile offspring and B and C do, but A and C do not? The whole definition of species falls apart (it leads to a paradox).
We have a lot of that in biology. You need to learn to deal with it (sunglasses dropping down), and assign uncertainties to terms you learn about, they are often just our attempts to name boxes on continuous, multidimensional scales.
Well, what is suboptimal... One would engineer it differently, it makes a weird, seemingly unnecessary, loop around some other tracts. However, being a biologist I can also imagine that if we'd reroute the thing in someone using surgery, that person suddenly gets more infections because bacteria find their way up the tract more easily (no idea, but could be!). The point is... It's a mess based on some earlier mess, but it works, and changing one part in this mess can lead to unpredictable results.
As for "discontinuous evolution"... Again, what is discontinuous? I'm sure there are events to be found of which the probability of them occurring is so small and the effects so large that they'd fall into someone's definition of "discontinuous". But I think there is by definition no such thing as discontinuous evolution. If it occurred, it had a non-0 probability of occurring, then again, maybe the universe is infinite and everything has a non-zero probability of occurring. This is getting philosophical haha. Maybe listen to some Mindscape podcasts (Sean Caroll).
Actually rabbits eat their excrement again. That's also probably not how an engineer would make it (or an intelligent designer would design it, since we seems to be going in that direction ;) ).
Great question! It maybe can be, but what is the maxima that is being solved for exactly? There are usually tradeoffs, the most common and prevalent is our body's immune response. If it's under-active, we might die from an infection. If it's over-active, we get diabetes, lupus, chron's, and (probably) lots of mental health disorders.
So, it's a bit context dependent, and definitely dependent on other mutations that have occurred in other parts of your DNA. Most complex diseases are "polygenic", meaning it's a culmination of quite a few factors that would contribute to a specific good or bad outcome.
So, yes, it could be modeled as a sort very context dependent with a lot of highly correlated non-independent covariates. We do use quite a lot of statistical and ML methods to understand the genome (I work in statistical genetics), but the complexity of biology has so far proved a tough nut to crack.
Evolution is the ultimate "good enough". Once the required threshold is passed, pressure stops. The threshold might constantly be moving due to competition, environment etc.
>“No way. They’re partying all night.” But they can, because there’s no top-down pressure to go into the office at 8 a.m. They’re free to catch supplemental sleep as needed throughout the 24-hour period.
This feels like the key point to me. These societies follow their body and go to sleep when they are tried, while us in the west have to sleep at a specific time to fit our schedules.
>18 degrees Celsius is considered optimal for sleep depth
I'm instantly skeptical of anyone making universal statements like this, because they're certainly not true for everyone, and having looked into these and similar (f/x "ideal room/office temperature"), are based on many entangled assumptions. Most of the time I expect it's just people making after-the-fact justification for doing (or imposing) what they most prefer.
When statements like this are made usually it’s because studies would have been done comparing sleep depth at different temperatures and there would have been a statistically significant increase in sleep depth at 18 degrees Celsius in the tested group compared to groups sleeping at other temperatures.
I have no idea if that was actually done here but that’s usually how these statements are justified.
Of course we are all individuals so it may not apply to everyone but you can say that for everything in medicine. Only thing we can do is look for statistically significant differences between groups in double blind controlled studies after controlling for all other factors.
If they have no frame of reference then it seems like their general contentedness is being measured (or as another commenter indicated, their willingness to gripe.)
They're probably also less confronted with articles/videos/social media posts telling them they're doing it wrong and how they should sleep instead. Sometimes ignorance (or rather, not overthinking things) is bliss...
Well probably us modern human only know the "8h sleep at night" kind of sleep, yet a lot of people would tell you whether they're satisfied or not with their sleep
I mean I can vary from 9 to 3 hours of sleep a night, and I can tell you I'd rather get 9 than 3. Just because I'm meant to get 8 hours a night doesn't mean I do
This interview feels weird to me, maybe because there's lots of places where I'm thinking there's an obvious idea that isn't raised.
Like, it seems obvious to me that sleep has a higher opportunity cost in humans than most other animals. So naturally there's more evolutionary pressure in humans to sleep more efficiently.
Is this actually true? Dunno! But it was really weird that it doesn't get brought up.
> Some emerging research suggests Earth’s magnetism matters, as well. Being barefoot on the ground versus 30 stories high in a downtown skyscraper puts you in a completely different magnetic environment.
Really? My instinctive reaction to this statement is that it's quackery. Would be very interested to see headlines appear about this if it's true.
It's definitely quackery. There's way more "natural" magnetic variation between two different cities than between a ground floor apartment and a 30th floor apartment (see magnetic declination maps), and that's even before you get into the way-more-powerful magnetic fields generated or present in a home.
People already live in different altitudes, ie with vastly different amounts of rock between themselves and the bits of the earth that produce her magnetic field.
So colour me skeptical of this claim as well.
And while I like going barefoot for other reasons, I don't think it makes much of a difference to the magnetic fields.
> People already live in different altitudes, ie with vastly different amounts of rock between themselves and the bits of the earth that produce her magnetic field.
It's not really the same thing. Construction and especially the high content of charged metal (whether it's power conduits or plain old frame) may make a considerable difference.
Do many people sleep in such tall buildings? Obviously they exist, but I can't think of any over-20 story residential building I've ever been in. Office space, sure, but not residential.
More fragmented sleep, with people talking in the night, etc. I guess that's different from the low, unnatural, rumbles of cars and aeroplanes the majority of people have to put up with.
The article title is "Where human sleep went wrong" but then the entire article is about how we sleep the best we ever have, we have the most high quality sleep, and all the fearmongering about sleep is basically wrong.
> Sleep is critical to human functioning, and yet, we sleep fewer total hours than any other ape, and are still arguably the most evolutionarily successful of the primates
> humans are weird outliers—we’re the shortest sleeping primates, yet we pack in the most REM sleep relative to this short duration
Isn't that sort of the point? Sleep is a detrimental necessity and the more efficient an organism is in needing less of it, the more effective it can be because it simply has more time to get ahead of the others?
It's still very odd that no species has ended up evolving a continuous maintenance system that can run while conscious, the benefits when hunting other animals that need sleep would be enormous, so there has to be significant evolutionary push for it. I suppose the single hemisphere sleep some marine mammals do is part of the way there, but it is at most a lazy workaround. Practically all other organs have evolved to run 24/7 for up to a century without a single break, what makes brains so universally different?
> It's still very odd that no species has ended up evolving a continuous maintenance system that can run while conscious
Great point. Afaik, our bodies do preserve energy when we sleep/rest. A few questions that needs to answered first:
- will gains of 24/7 hunting/foraging offset the extra energy costs? Lions sleep 16-20 hours a day, according to the internet.
- do continuous maintenance systems imply duplicate systems? If so, I have a hunch that even a mere 40% increase in energy expenditure would quickly undo the gains in waking hours.
> It's still very odd that no species has ended up evolving a continuous maintenance system that can run while conscious, the benefits when hunting other animals that need sleep would be enormous, so there has to be significant evolutionary push for it.
I disagree. Endurance hunters walk an animal down throughout a single day. Sleep isn't the bottleneck. Efficient bipedalism and sweat are enough.
Unihemispheric sleep has been used by cults for mind control because it puts you in a vulnerable mental state (for example https://zizians.info/#unihemispheric-sleep). So anybody reading this and interested in trying it, ensure you’ve done sufficient research first.
The fact they electrically signal via chemical analogs fuelled by immersion in nutrient bearing fluid that also accretes waste products, yet is kept separate from the primary loop of the cardiovascular system by the blood-brain barrier?
> untangle what he calls the sleep paradox: Sleep is critical to human functioning, and yet, we sleep fewer total hours than any other ape
Instead of going to Tanzania you could’ve asked a sleep scientist. Sleep length has no known correlation to brain size and is known for drastic within family variation. What’s more sleep has a high within species variation too, some sleepers can survive 4 hours, others need 8. Collectively we used to sleep 9 hours in the 20th century, but it appears shorter sleep is fine too.
TLDR: no one has any idea why sleep length varies and he won’t find his answers in antrophological studies in Tanzania, though luck, buddy
I think people in HN (and in general) have to remember the central axes of evolution before digesting this kind of article. I've already seen comments like it's "odd that no species has ended up evolving a continuous maintenance system" and "sleep has a higher opportunity cost in humans" in this comments section.
This is a common, but poor framing of evolution. Remember: the only real rule with evolution is "did this evolutionary change mean they survived / reproduced more"? Evolution is not a local or global maxima solving function. I find this kind of attempt at interpreting selection common with engineers, programmers, etc.
Did their genes survive more, you mean. Hyper-vigilance could be maladaptive for the individual and still survive if it benefits others that carry the gene for it.
A bit of a digression, but I recently learned about the concept of pangenomes, of trying to map not just the genes in one individual, but the entire set of genes from a clade. It seems it matters a lot in practice for e.g. the immune system that we don't all have the same surface proteins on our cells, even if done some surface proteins are clearly better than others.
I can see why it isn't a local or global maxima solving function, but it surely can be modelled by one, right?
I'm a biologist so forgive me the poor wording, but there are "infinitely high" peaks/walls in the evolutionary landscape, as in: "the human urinary system has some evolutionary constraints and anatomical features that are not optimally designed from an engineering perspective, but they are generally functional and reflect our evolutionary history rather than deliberate design." <- this is from AI, I didn't remember the details, but the ureters or urethra take a long way around the inner part of the body because at some point it was a good route, but as we evolved it became suboptimal, but we can't just evolve to untangle all the pipes in our body and do some cable management... We're stuck with what we have (no tunneling electrons ;)).
So in that sense, a global maxima (minima?) solving function will probably not arrive at what we have, it has to take into account our evolutionary path, in its entirety (as in the whole tree.), because it is all encoded in 1 (or several) long molecules, and a radical changes would take a rewrite of many parts at the same time, which just does not happen. Maybe at some point we can do it ourselves... though I imagine there being a lot of unintended consequences in other places in the body :).
Another example is that sometimes complexity in a cell signalling cascade is simply there to get some timing right (ie delay some response), and the complexity is just there, and won't simplify by itself -> But then later the complexity may start to serve some purpose. Just like proteins that are "copypasta-ed" in the genome, leaving one copy free to mutate and attain a function, or not... etc etc.
“recurrent laryngeal nerve” as well
https://futurism.com/evolutianary-proof-the-recurrent-laryng...
That is the difference between global and local optima. We're not at a local optimum though, our bodies can probably evolve to produce half the urine or something without changing the route, but there is no evolutionary pressure to do so.
Yes, but we cannot evolve to have our urinary tracts take a more efficient route (or at least the probability is exceedingly low), even though there would be pressure to do so. (Maybe I'm misunderstanding your point)
Interesting
I did not know human urinary tract was suboptimal.
Are there examples of "discontinuous" evolution where a chance mutation stumbled upon a much better way to do something that allowed a species to jump the gap?
I imagine it would be very rare because chance mutations in a single individual that confer extraordinary survival / mating advantage to offset entire population would be rare like being a superman among men.
"I imagine it would be very rare because chance mutations in a single individual that confer extraordinary survival / mating advantage to offset entire population would be rare like being a superman among men."
-> This also depends on population size, if there is a bottleneck event (ie 99.99 percent of some species dying) then among the 100's of survivors perhaps there could be a superman. Either because this person got lucky, or the rest got unlucky. But in general the distribution of traits is quite continuous, given large populations.
It's also good to keep in mind that us biologists have messy definitions, ie we call specimen A and B the same species when they produce fertile offspring. Some species produce offspring but infertile (Horse-Donkey, Lion-Tiger). But what if A and B have fertile offspring and B and C do, but A and C do not? The whole definition of species falls apart (it leads to a paradox).
We have a lot of that in biology. You need to learn to deal with it (sunglasses dropping down), and assign uncertainties to terms you learn about, they are often just our attempts to name boxes on continuous, multidimensional scales.
Well, what is suboptimal... One would engineer it differently, it makes a weird, seemingly unnecessary, loop around some other tracts. However, being a biologist I can also imagine that if we'd reroute the thing in someone using surgery, that person suddenly gets more infections because bacteria find their way up the tract more easily (no idea, but could be!). The point is... It's a mess based on some earlier mess, but it works, and changing one part in this mess can lead to unpredictable results.
As for "discontinuous evolution"... Again, what is discontinuous? I'm sure there are events to be found of which the probability of them occurring is so small and the effects so large that they'd fall into someone's definition of "discontinuous". But I think there is by definition no such thing as discontinuous evolution. If it occurred, it had a non-0 probability of occurring, then again, maybe the universe is infinite and everything has a non-zero probability of occurring. This is getting philosophical haha. Maybe listen to some Mindscape podcasts (Sean Caroll).
Actually rabbits eat their excrement again. That's also probably not how an engineer would make it (or an intelligent designer would design it, since we seems to be going in that direction ;) ).
Great question! It maybe can be, but what is the maxima that is being solved for exactly? There are usually tradeoffs, the most common and prevalent is our body's immune response. If it's under-active, we might die from an infection. If it's over-active, we get diabetes, lupus, chron's, and (probably) lots of mental health disorders.
So, it's a bit context dependent, and definitely dependent on other mutations that have occurred in other parts of your DNA. Most complex diseases are "polygenic", meaning it's a culmination of quite a few factors that would contribute to a specific good or bad outcome.
So, yes, it could be modeled as a sort very context dependent with a lot of highly correlated non-independent covariates. We do use quite a lot of statistical and ML methods to understand the genome (I work in statistical genetics), but the complexity of biology has so far proved a tough nut to crack.
Great answer! Thank you!
Evolution is the ultimate "good enough". Once the required threshold is passed, pressure stops. The threshold might constantly be moving due to competition, environment etc.
To be precise inclusive genetic fitness not idealized bayesian optimality.
>“No way. They’re partying all night.” But they can, because there’s no top-down pressure to go into the office at 8 a.m. They’re free to catch supplemental sleep as needed throughout the 24-hour period.
This feels like the key point to me. These societies follow their body and go to sleep when they are tried, while us in the west have to sleep at a specific time to fit our schedules.
A single block of sleep is a relatively new behaviour, I suspect partially driven by the availability of cheap sources of light and heat. https://www.bbc.com/future/article/20220107-the-lost-medieva...
This is a contentious theory with little actual historical backing. Most likely people have been sleeping in one block since forever.
> Most likely people have been sleeping in one block since forever.
Does that have stronger historical backing?
That theory is on rather shaky grounds: https://pmc.ncbi.nlm.nih.gov/articles/PMC10404514/
>18 degrees Celsius is considered optimal for sleep depth
I'm instantly skeptical of anyone making universal statements like this, because they're certainly not true for everyone, and having looked into these and similar (f/x "ideal room/office temperature"), are based on many entangled assumptions. Most of the time I expect it's just people making after-the-fact justification for doing (or imposing) what they most prefer.
When statements like this are made usually it’s because studies would have been done comparing sleep depth at different temperatures and there would have been a statistically significant increase in sleep depth at 18 degrees Celsius in the tested group compared to groups sleeping at other temperatures.
I have no idea if that was actually done here but that’s usually how these statements are justified.
Of course we are all individuals so it may not apply to everyone but you can say that for everything in medicine. Only thing we can do is look for statistically significant differences between groups in double blind controlled studies after controlling for all other factors.
>the Hadza uniformly reported high satisfaction with their sleep.
And why wouldn't they? This is (presumably) the only kind of sleep they know.
Do you really need to know other kinds of sleep in order to know if you feel like shit after waking up or if you feel fine?
If they have no frame of reference then it seems like their general contentedness is being measured (or as another commenter indicated, their willingness to gripe.)
They're probably also less confronted with articles/videos/social media posts telling them they're doing it wrong and how they should sleep instead. Sometimes ignorance (or rather, not overthinking things) is bliss...
Also, they may not want to complain to strangers.
Also, we humans can get used to a lot of things and just be okay with it. For an extreme example, look at domestic abuse victims...
Well probably us modern human only know the "8h sleep at night" kind of sleep, yet a lot of people would tell you whether they're satisfied or not with their sleep
I mean I can vary from 9 to 3 hours of sleep a night, and I can tell you I'd rather get 9 than 3. Just because I'm meant to get 8 hours a night doesn't mean I do
This interview feels weird to me, maybe because there's lots of places where I'm thinking there's an obvious idea that isn't raised.
Like, it seems obvious to me that sleep has a higher opportunity cost in humans than most other animals. So naturally there's more evolutionary pressure in humans to sleep more efficiently.
Is this actually true? Dunno! But it was really weird that it doesn't get brought up.
> Some emerging research suggests Earth’s magnetism matters, as well. Being barefoot on the ground versus 30 stories high in a downtown skyscraper puts you in a completely different magnetic environment.
Really? My instinctive reaction to this statement is that it's quackery. Would be very interested to see headlines appear about this if it's true.
It's definitely quackery. There's way more "natural" magnetic variation between two different cities than between a ground floor apartment and a 30th floor apartment (see magnetic declination maps), and that's even before you get into the way-more-powerful magnetic fields generated or present in a home.
You can write pretty much anything you want after “Some emerging research suggests”
More evidence this may have been written by a pigeon...
People already live in different altitudes, ie with vastly different amounts of rock between themselves and the bits of the earth that produce her magnetic field.
So colour me skeptical of this claim as well.
And while I like going barefoot for other reasons, I don't think it makes much of a difference to the magnetic fields.
> People already live in different altitudes, ie with vastly different amounts of rock between themselves and the bits of the earth that produce her magnetic field.
It's not really the same thing. Construction and especially the high content of charged metal (whether it's power conduits or plain old frame) may make a considerable difference.
What about flowing underground water when sleeping on the ground?
What about the metal frame of a bed?
Do many people sleep in such tall buildings? Obviously they exist, but I can't think of any over-20 story residential building I've ever been in. Office space, sure, but not residential.
See https://en.wikipedia.org/wiki/The_Pinnacle@Duxton
The amount of people who would regularly sleep in such a building is a minuscule fraction of the world population.
And Earth's magnetic field is extremely weak
There might be precedent for being able to detect changes in magnetic field
https://www.pbs.org/newshour/science/dogs-poop-in-alignment-...
but then again maybe not
https://www.sciencedirect.com/science/article/abs/pii/S15587...
It's a creative innovation!
More fragmented sleep, with people talking in the night, etc. I guess that's different from the low, unnatural, rumbles of cars and aeroplanes the majority of people have to put up with.
737s are fine its dog barking that gets me.
I could only wish for low unnatural rumbles of cars. In 3rd world countries it's non stop horns and noisy motorbikes
Car horns gotta be up there as some of the worst inventions of the 20th century, noise pollution galore.
It works when you have strict rules on the use of horns and people get peer pressured into adapting to the behavior of their surroundings.
I actually find it easier to sleep with the sound of people talking around me, it's very comforting.
A nap is the same as sleep, but we don't do this. Any correlation to our southern american friends and their siestas?
The article title is "Where human sleep went wrong" but then the entire article is about how we sleep the best we ever have, we have the most high quality sleep, and all the fearmongering about sleep is basically wrong.
> Sleep is critical to human functioning, and yet, we sleep fewer total hours than any other ape, and are still arguably the most evolutionarily successful of the primates
> humans are weird outliers—we’re the shortest sleeping primates, yet we pack in the most REM sleep relative to this short duration
Isn't that sort of the point? Sleep is a detrimental necessity and the more efficient an organism is in needing less of it, the more effective it can be because it simply has more time to get ahead of the others?
It's still very odd that no species has ended up evolving a continuous maintenance system that can run while conscious, the benefits when hunting other animals that need sleep would be enormous, so there has to be significant evolutionary push for it. I suppose the single hemisphere sleep some marine mammals do is part of the way there, but it is at most a lazy workaround. Practically all other organs have evolved to run 24/7 for up to a century without a single break, what makes brains so universally different?
- will gains of 24/7 hunting/foraging offset the extra energy costs? Lions sleep 16-20 hours a day, according to the internet.
- do continuous maintenance systems imply duplicate systems? If so, I have a hunch that even a mere 40% increase in energy expenditure would quickly undo the gains in waking hours.
> It's still very odd that no species has ended up evolving a continuous maintenance system that can run while conscious, the benefits when hunting other animals that need sleep would be enormous, so there has to be significant evolutionary push for it.
I disagree. Endurance hunters walk an animal down throughout a single day. Sleep isn't the bottleneck. Efficient bipedalism and sweat are enough.
There's a similar mechanism called USWS https://en.wikipedia.org/wiki/Unihemispheric_slow-wave_sleep (Half of the brain remains awake while the other sleeps, not an expert so please correct if wrong)
Unihemispheric sleep has been used by cults for mind control because it puts you in a vulnerable mental state (for example https://zizians.info/#unihemispheric-sleep). So anybody reading this and interested in trying it, ensure you’ve done sufficient research first.
The fact they electrically signal via chemical analogs fuelled by immersion in nutrient bearing fluid that also accretes waste products, yet is kept separate from the primary loop of the cardiovascular system by the blood-brain barrier?
But why is that fundamentally different from the technobabble description of any other vital organ?
> untangle what he calls the sleep paradox: Sleep is critical to human functioning, and yet, we sleep fewer total hours than any other ape
Instead of going to Tanzania you could’ve asked a sleep scientist. Sleep length has no known correlation to brain size and is known for drastic within family variation. What’s more sleep has a high within species variation too, some sleepers can survive 4 hours, others need 8. Collectively we used to sleep 9 hours in the 20th century, but it appears shorter sleep is fine too. TLDR: no one has any idea why sleep length varies and he won’t find his answers in antrophological studies in Tanzania, though luck, buddy
How do you think sleep scientists got their data in the first place? Some of them went to Tanzania.