Recent comments in /f/askscience

Georgie___Best t1_j9j3r5b wrote

Reply to comment by Krail in when a limb gets amputated, how do they stop the flow of blood? by EnchantedCatto

Capillaries are very small. We are talking of a scale where red blood cells might only fit through single file. At this microscale, diffusion/osmosis are what predominantly facilitates the movement of useful stuff out of the blood and into the extracellular fluid/cells, and waste back into the blood vessels to be taken away.

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Unicorn_Colombo t1_j9j3r3a wrote

Reply to comment by VT_Squire in Why can’t mules reproduce? by Imaginary_Camel4213

> The term "hybrid" exists for this very reason. It's to specify the product of two species, which is imbued by nature with DNA compatibility issues that either partially or entirely prohibit the free diffusion of genes into a receiving population. In short, that example of offspring (mules, in this case) is not "viable" by definition.

This is not correct. Hybrid doesn't imply in any way that the offspring are "not viable by definition".

See the etymological origin of the word: https://www.etymonline.com/word/hybrid

or scientifically its scientific use, as hybrid is used for any crossproduct, such as a hybrid breeds, plant varieties, and also species. Hybridization is very common in plants and doesn't automatically lead to non-viability of the F2 generation. In fact, up until modern times with industrial agricultural techniques, doing something like that would be crazy (unless the plants could be propagated in other way), but nowadays seedless fruit is considered something desirable.

It just happens that when we consider species hybrids among animals we get infertility. But again, there are other kinds of hybrids and taxonomy is absolutely arbitrary. There are circular species, species groups and other kinds of things, that can breed between themselves without problem.

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TheDevilsAdvokaat t1_j9j3lgp wrote

Reply to comment by CletusDSpuckler in What are more accepted hypotheses that similarly explain the aspects of hominid evolution that the "pseudoscientific" aquatic ape theory does? by KEVLAR60442

Sometimes things we think are weird quirks actually have benefits we just haven't realised.

There's a severe cost for females having babies with older males. It's well known that over a certain age, babies from older men have increased problems.

As the father grows older, the number of mutations in the father's genome increases, leading to an increase in the incidence of congenital malformations in offspring [11, 65]. Older paternal age may be harmful to the offspring's health in terms of genetic mutations, telomere length, and epigenetics

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7803514/#:~:text=As%20the%20father%20grows%20older,%2C%20and%20epigenetics%20%5B66%5D.

But how do you easily tell or estimate a male's age? Well, what about a signal like graying? Imagine if there was a signal that was almost universal among males, easy to spot at a glance, and a decent general guide to age?

I suspect graying is NOT a "weird quirk". It's just one we didn't realise the benefit of. There could be other good reasons for graying too. Graying may be an "honest signal" like stotting.

https://en.wikipedia.org/wiki/Signalling_theory#Honest_signals

I suspect there are a lot less "weird quirks" than people think; just misunderstood adaptations.

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LORD_HOKAGE_ t1_j9j30kt wrote

Reply to What makes bats a good disease vector? by JustJustinInTime

When normal animal gets sick, it dies. The body dies, so the viruses in the body can’t go anywhere and die also. Disease not spread

When bats get sick, it doesn’t hurt them. They survive and the virus in them gets to grow and mutate and eventually evolve to jump species and infect humans because the bat is alive flying around humans or being ate by humans

Where other animals would get sick and die, ending the viruses spread, bats easily survive virus’s thus are able to incubate them and spread them around

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HungerISanEmotion t1_j9j0ybu wrote

Reply to comment by DecafWriter in What makes bats a good disease vector? by JustJustinInTime

So viruses hoping from bats to humans have a greater potential to be deadly then viruses which hop from human to dogs. Wouldn't this create a bias because... viruses hoping from bats would get much more attention, and viruses hoping from dogs, pigs, cows would be mostly benign and remain undetected.

Or in other words, bats are not a good virus vector at all, instead they are a vector for deadly viruses.

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Daberino t1_j9j07er wrote

Reply to What makes bats a good disease vector? by JustJustinInTime

Bats are a species that live in extremely close quarters. Say a viral disease is using them as a reservoir, this greatly increases its ability to transmit itself to other bats via aerosol or guano. This allows the virus to go through mutagenic changes in its genome to overcome host defense or increase transmittance. As mutations in the genome are driven by pressure or random chance. Now, the virus has both what it needs which is reproduction due to the large number of bats but also since bats are mammals it puts them a little bit closer in terms of protein expression compared to humans. Both bats and humans have similar protein receptors which viruses exploit to gain access to the cell. So, its easier for a virus to make the jump from a bat to a human. Bats are also ubiquitous among landscapes. This tends to give them proximity to humans. Like your rats in your example of bubonic plague. Therefore, contact between bats and humans is unavoidable.

I hope I was able to answer your question!

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anakro22 t1_j9iyxm7 wrote

Reply to What are more accepted hypotheses that similarly explain the aspects of hominid evolution that the "pseudoscientific" aquatic ape theory does? by KEVLAR60442

I don't know of any 'more accepted hypothesis' that explains it better than AAT, because, for a lack of a better word, we simply have none. The main reason why we humans are here and why not some gorillas instead of us, are our brains. The only reason why we are so smart is docosahexaeionic acid, DHA, primarily and mostly in human diets because of fish and shelfish, as it is produced by algae in marine environments. We do not see human-like brain development in land-mammals. Any animal, not getting enough DHA and living on land, tends to get 'big', but not smart. The reason for that is that in the land-based food chain there simply is no DHA available for brain growth. For humans, seafood probably was the only constantly available food resource and once we learned to digest and aquire it, our development from other apes diverged. And all of this, just because of our brain, I haven't even mentioned the fact that babies can swim before they learn to walk etc., etc., which clearly shows hominids being semi-aquatic for a long time before settling down.

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