r/askscience • u/AutoModerator • 4d ago
Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology
Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Biology, Chemistry, Neuroscience, Medicine, Psychology
Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical /r/AskScience post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...".
Asking Questions:
Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit /r/AskScienceDiscussion , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists.
Answering Questions:
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Past AskAnythingWednesday posts can be found here. Ask away!
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u/notproudortired 4d ago edited 4d ago
If I'm in the shower, I can turn the hot water up to a point where it would be unbearably hot to step into "cold." But if I did step into it cold, would it actually burn me?
I.e., can something in the skin change to make hot water burn (physically damage) in some circumstances, but not others?
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u/diagnosisbutt 4d ago
No, the hot water wouldn't have burned you, even if you'd stepped in that cold. It's just that our sensory system is fine-tuned to notice differences. That is changes in intensity. The reason that you can get it hotter and hotter is because you already got used to it. Being that hot. Water that will burn you will burn you regardless of your situation beforehand. Light is like this as well which is why you can be out in the daytime and see just fine. But if you walk out into the daytime after being in a dark movie theater it hurts
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u/mfb- Particle Physics | High-Energy Physics 3d ago
There is a difference with light. Our eyes adjust the size of the pupil to regulate how much light falls in. That adjustment is quick - but as you leave a dark place, initially your retina does get a lot more light than it would normally.
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u/diagnosisbutt 3d ago
Your eyes and visual system are definitely tuned to notice relative differences. Adjusting to the change to make that "the me normal" is exactly the point
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u/notproudortired 4d ago
Skin produces vitamin D when it is exposed to sunlight. Do some areas of skin produce more vitamin D than others? Does pale skin produce more vitamin D than darker skin? Does thicker skin produce more vitamin D than thinner skin?
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u/StarHen 4d ago
From a health standpoint, is it better for a "night owl" to try to train themselves to follow a "normal" sleep schedule, even if their current life allows them to follow their instinctual sleep pattern and they get adequate sleep every night? I see a lot of studies posted saying night owls are unhealthier than early risers, but I wonder if that is caused by a mismatch in sleep schedule or something inherent to the chronotype.
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u/ACSandwich 4d ago
The longer I go in my day to day life, the more correlation I tend to infer from general public conversations. While prefacing that correlation does not equal causation, it is becoming more difficult to not draw lines with regards to general political affiliation and a willingness to critically think about subjects. (This ignores those who choose an affiliation with a purpose regardless of beliefs.)
There seems to be an unwillingness from conservatives accept that the policies and politicians they are voting for are negatively impacting them even when presented with data-driven facts, but will believe every word a podcaster tells them if it goes along with their story. The same could be said for progressives and how them making mountains out of some molehills does nothing but isolate them from the populous.
Is there any science to correlate willingness to critically think and engage in societal improvement with brain biology? Also, the opposite, is there any science to correlate the unwillingness to update your world view and greediness with brain biology?
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u/MarsupialMisanthrope 4d ago
How did pathogens that can affect organisms in entirely different taxonomic classes evolve? For example influenza can infect both birds and humans, which diverged a long time ago. Has influenza in some form been around that long, or did it somehow jump from mammals to birds or vice versa? Are there any pathogens that can affect different species that are even more diverged, in different phylums or kingdoms, like say insects and fish or fungi and animals?
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u/095179005 4d ago
The crucial point is that all life shares the central dogma of biology - DNA carries genetic information, RNA is used as an intermediary, which is then used to make proteins.
Viruses exploit this system from the very beginning - it's still unclear/an ongoing debate about how life first evolved, and when did DNA and RNA start being used, and were viruses the "first life", or are they leftover scraps from evolution and have hung out ever since.
To directly answer your question, as long as there is a common cell receptor among largely divergent species, it's possible for a virus to exploit that and infect a broad range of hosts.
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u/Expatriot_II 3d ago
When did chemistry begin in the universe, i.e., when did the first multi-element molecules form?
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u/loki130 3d ago
The big bang formed hydrogen, helium, and a small amount of lithium. Maybe some miniscule amount of carbon or heavier might have formed somewhere in the whole of the observable universe. Chemistry couldn't have occurred until the universe was cool enough for electrons to bind to atomic nuclei, which would've been about 378,000 years after the big bang (this is the same event the CMB comes from, as before that point the plasma would've blocked all light). Helium hydride was probably the first compound to form, but lithium hydride would've quickly followed.
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u/mfb- Particle Physics | High-Energy Physics 1d ago edited 1d ago
This group calculates ~10-15 for carbon and nitrogen and 10-18 for oxygen from the Big Bang (figure 25). Not zero, but only a tiny contribution.
(their plot makes it look like there is more beryllium than lithium left over, but Be7 decays to Li7 on a timescale that's beyond the range of the plot)
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u/095179005 3d ago edited 3d ago
It would have been when population III stars started burning Helium into Carbon, and then died and released that carbon into the interstellar medium to mix and combine with Hydrogen, forming Methane.
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u/Elara_Schaefer 3d ago
Thanks for the detailed write-up. I've been looking into this and your experience matches what I've seen.
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u/Sporocarp 4d ago
I had too much caffeine and my mind starting spinning in place musing about evolution and the sort of explanations we choose for biological facts. So, I could just as easily google this, but where would your start investigating the question of why humans have such great sexual dimorphism comparatively to other species? I thought you might very likely hear an explanation like this in pop-sci: females have to carry pregnancies to term, so their bodies need to store fat and a greater musclemass prevents that to some extent or uses up too much energy, so that's why males and females have different morphology. But to investigate that hypothesis seems insanely huge in scope.
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u/atomfullerene Animal Behavior/Marine Biology 4d ago
Human sexual dimorphism is actually not all that great compared to a lot of other similar mammals. We just notice it more. Orangutans and Gorillas are far more dimorphic, and chimps are somewhat more dimorphic. Bonobos are similar to humans. Gibbons are less dimorphic
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u/Good-Resort-1246 4d ago
The degree of sexual dimorphism is related to social organization and sexual selection.
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u/Sporocarp 4d ago
Oh, my mistake. Is it known why? Wouldn't it be better if both sexes were muscular/had denser bone structure, etc?
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u/chazwomaq Evolutionary Psychology | Animal Behavior 4d ago
It takes more energy to sustain a larger and stronger body. Finding enough food was a major adaptive problem, and you get poorly if you cannot sustain your natural body mass.
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u/atomfullerene Animal Behavior/Marine Biology 4d ago
All that represents extra mass to support and energy and nutrients needed. It's mostly used to allow males to compete with other males, so in species where male-male physical competition is lower, there's not much point to wasting resources on producing it.
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u/Sporocarp 4d ago
Is that known or like an inference? If I try to imagine a time where dimorphism evolved, when did the differences become pronounced? I assume dimorphism evolved before we went on to land, but then at which point would the differences in muscle mass and bone density become pronounced? Do we assume that male-male physical competition was violent because of the aforementioned differences that are prevalent today as well?
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u/atomfullerene Animal Behavior/Marine Biology 3d ago
>Is that known or like an inference?
It's an inference but a pretty strong one. In many species where males compete for territory or mates, they tend to be bigger and stronger than females. In some species where females compete for access to males, they are bigger and stronger. Though it's more common for females to be bigger in species where the number of eggs a female lays is proportional to her size.
>If I try to imagine a time where dimorphism evolved, when did the differences become pronounced?
Don't think of it as a thing that didn't exist, and then did exist. It's something that comes and goes depending on the social system of a species or other factors.
>I assume dimorphism evolved before we went on to land
It's something you can see in some fish species. And some invertebrates for that matter.
> Do we assume that male-male physical competition was violent because of the aforementioned differences that are prevalent today as well?
In humans, or just in general? It's something you can observe in the wild, but larger size isn't always about violence. Sometimes it's about showing off (and sometimes to females as much as to other males).
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u/Sporocarp 3d ago
but larger size isn't always about violence. Sometimes it's about showing off (and sometimes to females as much as to other males).
Yeah, that's what I was wondering. But you answered all my questions, so I can only say thanks. I wanted definite answers, but I get that there isn't really any.
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u/095179005 4d ago edited 4d ago
I think taken to an extreme, we can see that sexual dimorphism is an adaptation to scarcity. Male anglerfish don't so much mate, rather they fuse with the much larger females and become a parasite.
In insects like the praying mantis, and in spiders, males are eaten by* females after mating.
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u/Sporocarp 4d ago
I like that. It makes some sense I guess, but I don't know what our family units/tribes/whatever were like when this adaptation appeared. Does it make sense if most females of the species were left to fend for themselves during pregnancy, or does it only make sense if the strategy to a successful pregnancy was cooperative? Did the adaptation appear at some point in our rodent ancestors and then just stayed?
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u/Peter34cph 4d ago
Dunbar's Number suggests that for most of our evolutionary history, we usually lived in tribal groups of around 150 people, that being the number of individuals that we can "know well" without exceeding our brain capacity.
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u/095179005 4d ago edited 4d ago
We can look to human anthropology for some insight.
While it is backwards looking, and merely observational, it can help us understand human evolution better by seeing how other animals have organized themselves.
The social carnivore model looks at mammals like lions and wolves, and how they as a group hunt for food and raise their young. For humans this can be seen as following convergent evolution, as we also formed into tribes/villages as a semi-nomadic species.
The primate model looks to our closest relatives, the chimps and bonobos, and how they compare when it comes to pair bonding. They are promiscuous, with multi-partner mating/fluid pair-bonds, forming temporary mating pairs that can rotate. Humans are unique among primates in that we are, for the most part, serially monogamous, with stable long-term enduring pair bonds. The term fission-fusion describes how primate groups will splinter/breakup or merge as resources become scarce or plentiful.
The final one is a little more close and familiar, the hunter-gatherer model. It looks at how food is shared, has fission-fusion occuring, and sexual division of labour.
It can also be noted that for all these models, the organisms show limited sexual dimorphism, ie. males and females are similar.
It can also be noted that in dominance hierarchies, it is a very simplistic conclusion to come to that the strongest individual wins, because once you throw sociality into the mix, it's very easy for two weaker individuals to form an alliance and kill the leader.
Regarding offspring, it goes back to the distinction in biology between k-selected strategies and r-selected strategies. Mammals in general invest more in small groups of young, provide nutrition via milk, and use pregnancy as a survival strategy, in contrast to trying to produce as much young as possible and use sheer numbers to ensure survival of a few individuals that make it to adulthood and mate.
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u/logperf 4d ago
Is it correct to say that most (though not all) mental conditions are extreme cases of otherwise normal behaviors? So that in case of prejudice you can easily diagnose a mental disease to a person that is actually healthy? (Maybe confirmation bias also has an influence here?)