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Mysterious ‘super-archaic’ populations had multiple trysts with human ancestors

sciencemag.org

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Re: Mysterious ‘super-archaic’ populations had multiple trysts with human ancestors

#51

Post by ithkuil »

thaumasiotes wrote: post #19
chmod775 wrote: post #17

Earlier quoted context omitted.

>You can also observe how easily different species interbreed today, like wolves (canis lupus, obligatory pack animals) and coyotes (canis latrans, solitary). Their taxonomy predates the more modern biological classification systems though. Things have been reclassified before and I expect they will be again. [A bit of a rant:] Any classification system that can't tell you something about the objects it classifies is…

> Any classification system that can't tell you something about the objects it classifies is objectively useless for anything but naming things They are both canis , you know. The difference in species designation tells you very little because that's not a problem that can be solved. It's not an issue of misclassification. The specific designations latrans and lupus tell you a lot.

Canis is the genus. Even barring classification mistakes, cross-species breeding across genus is not impossible, it's just very less likely to produce viable and/or fertile offspring.

A classic example is the breeding between Equus Caballus (horse) and Equus Asinus (donkey): it works and you get a Mule.

The genetic difference between the horse and the donkey is non trivial, they even have a different number of chromosomes (64 vs 62). Since the offspring gets half of their chromosomes from the father and half from the mother, the mule gets an odd number of chromosomes (63) which clogs the gamete production machine and renders the animal sterile. (See https://genetics.thetech.org/ask/ask225).

Now, dogs and wolves don't have that problem. Does it mean they are same species and that the classification was applied to eagerly?

Re: Mysterious ‘super-archaic’ populations had multiple trysts with human ancestors

#52

Post by nobody9999 »

rsynnott wrote: post #30
chmod775 wrote: post #5

Earlier quoted context omitted.

This sentence doesn't make any sense: "H. sapiens doesn’t have the possibility of quickly grabbing a load of diversity by mating with another group". It would make sense if she specifically referred to Homo sapiens sapiens, but for Homo sapiens that "other group" would be of a different species and we thus we shouldn't be able to produce fertile offspring with them. Also Homo sapiens sapiens have plenty of genetic di…

> Also Homo sapiens sapiens have plenty of genetic diversity. Humans aren’t particularly genetically diverse, given our dispersal, though as far as I know there’s some disagreement on _why_.

>Humans aren’t particularly genetically diverse, given our dispersal, though as far as I know there’s some disagreement on _why_.

That's absolutely correct. One set of hypotheses about this are population bottleneck theories[0].

As an example, the Toba Catastrophe Theory[1] posits that:

"The Youngest Toba eruption has been linked to a genetic bottleneck in human evolution about 70,000 years ago,[28][29] which may have resulted from a severe reduction in the size of the total human population due to the effects of the eruption on the global climate.[30] According to the genetic bottleneck theory, between 50,000 and 100,000 years ago, human populations sharply decreased to 3,000–10,000 surviving individuals.[31][32] It is supported by some genetic evidence suggesting that today's humans are descended from a very small population of between 1,000 and 10,000 breeding pairs that existed about 70,000 years ago.[33][34]"

Whether such theories are correct or not, they appear to fit with the lack of genetic diversity among humans.

[0] https://en.wikipedia.org/wiki/Population_bottleneck

[1] https://en.wikipedia.org/wiki/Toba_catastrophe_theory#Geneti...

Re: Mysterious ‘super-archaic’ populations had multiple trysts with human ancestors

#53

Post by IIAOPSW »

mytailorisrich wrote: post #49
dfischer wrote: post #3

Interesting in the limelight of pandemics in regards to the closing paragraph: > Today, H. sapiens doesn’t have the possibility of quickly grabbing a load of diversity by mating with another group: For perhaps the first time in our history, we’re the only humans on the planet. It’s another reason to miss our extinct cousins, says population geneticist Carina Schlebusch of Uppsala University. “To have such a large den…

Even as the single human species we used to be spread into isolated groups, that's why different populations have specificities (e.g. skin colour, but also other adaptations). Now that we have such a huge and interconnected population diversity will fade and adaptation will slow.

I'm not so sure. Even with modern transportation technologies, the price of moving is still high enough that the number of single ethnicity births will generally outpace multi-ethnicity births. I don't think we have nearly enough airplanes and jet fuel to homogenize the genetics of ~8 billion people. But I also haven't run those numbers so feel free to change my mind.

Re: Mysterious ‘super-archaic’ populations had multiple trysts with human ancestors

#54

Post by bigbubba »

wincy wrote: post #36
interestica wrote: post #33

Earlier quoted context omitted.

I always wondered if there could be some sort of in-world explanation as to why all the aliens in star trek/wars are so ...humanoid.

I think it’s that all the worlds were seeded by some sort of progenitor race millions of years ago. Also they can interbreed I believe.

I guess the ancestors of humans aren't in Earth's fossil record in the Star Trek universe?

Re: Mysterious ‘super-archaic’ populations had multiple trysts with human ancestors

#55

Post by inglor_cz »

raducu wrote: post #46
holoduke wrote: post #14

Earlier quoted context omitted.

Covid is comparable to flu with a higher mortality rate. Don't make it bigger than it is. 99.95% of the people are doing perfectly fine. Genetics are thus pretty effective

Please, please, please stop saying that it is comparable to the flu in any way! I got a mild case of COVID-19, even the doctors in the hospital agreed on that; I was able to help other patients do stuff they couldn't, I could easily climb 2 floor worth of stair while 90% of the patients had to make frequent resting stops. 37 days after first symptoms, I'm still not back to my previous energy levels, I still cough, I…

"I got tinnitus in my right ear and pain when ejaculating."

Uh, thanks for warning, I guess? (nervously adjusting my FFP2 mask)

Re: Mysterious ‘super-archaic’ populations had multiple trysts with human ancestors

#56

Post by inglor_cz »

tzs wrote: post #40

> The story of human evolution is full of ancient trysts. Genes from fossils have shown that the ancestors of many living people mated with Neanderthals and with Denisovans, a mysterious group of extinct humans who lived in Asia In the case of Neanderthals, isn't that "all" people rather than "many" people? Neanderthals are believed to have gone extinct 40000 years ago. But there was an article here the other day abo…

Subsaharan Africans are believed not to have any Neanderthal admixture, and the logistics of the spread out of Africa would be a good reason why.

Re: Mysterious ‘super-archaic’ populations had multiple trysts with human ancestors

#57

Post by mytailorisrich »

IIAOPSW wrote: post #53
mytailorisrich wrote: post #49

Earlier quoted context omitted.

Even as the single human species we used to be spread into isolated groups, that's why different populations have specificities (e.g. skin colour, but also other adaptations). Now that we have such a huge and interconnected population diversity will fade and adaptation will slow.

I'm not so sure. Even with modern transportation technologies, the price of moving is still high enough that the number of single ethnicity births will generally outpace multi-ethnicity births. I don't think we have nearly enough airplanes and jet fuel to homogenize the genetics of ~8 billion people. But I also haven't run those numbers so feel free to change my mind.

A few instances of "new blood" in a population can be enough because it will then spread over generations.

In many countries the proportion of foreign-born is >10%, so the mixing is quite intense in terms of evolutionary time scales.

If that continues for a few hundreds of years, diversity will have significantly reduced. Indeed, some suggest that e.g. skin colour may largely homogenise within a thousand years.

A thousand years might sound like a very long time wrt. a single individual's lifespan, but for these issues it is nothing at all. In addition, some traits (e.g. pale skin colour) are quite recent from what we know.

Re: Mysterious ‘super-archaic’ populations had multiple trysts with human ancestors

#58

Post by corty »

IIAOPSW wrote: post #53
mytailorisrich wrote: post #49

Earlier quoted context omitted.

Even as the single human species we used to be spread into isolated groups, that's why different populations have specificities (e.g. skin colour, but also other adaptations). Now that we have such a huge and interconnected population diversity will fade and adaptation will slow.

I'm not so sure. Even with modern transportation technologies, the price of moving is still high enough that the number of single ethnicity births will generally outpace multi-ethnicity births. I don't think we have nearly enough airplanes and jet fuel to homogenize the genetics of ~8 billion people. But I also haven't run those numbers so feel free to change my mind.

Even if intercontinental interbreeding is still rare, societies and therefore breeding patterns have become far more connected on a local, national and intracontinental scale. Where there used to be the proverbial inbred populations in remote mountain valleys, mobility has completely erased the formation of such pockets. Same for marriages to other nationalities and religions. Where my german catholic grandmother might have gotten into trouble for marrying a protestant or a frenchman, nowadays that isn't a problem anymore.

Geographic variation will not dissappear completely, but the granularity and amplitude of those variations was and will continue to be smoothed a lot.

Re: Mysterious ‘super-archaic’ populations had multiple trysts with human ancestors

#59

Post by Ygg2 »

tsimionescu wrote: post #47
Ygg2 wrote: post #28

Earlier quoted context omitted.

Dr. Who is wrong. We could not mate with anything amongst the stars. Even if aliens exist they would be radically different. You might as well as bone your VCR. The act of separation would create new species. Not our drive to bone.

Given that we have absolutely no idea what other biological systems could look like, what you're saying seems extremely likely, but not an absolute certainty.

It's near certainty. I mean it's not absolutely certain that your nearest pencil won't transform into Jesus and tell you the message that will unite all of humanity. I kinda doubt you would entertain it though.

Re: Mysterious ‘super-archaic’ populations had multiple trysts with human ancestors

#60

Post by nmca »

IIAOPSW wrote: post #53
mytailorisrich wrote: post #49

Earlier quoted context omitted.

Even as the single human species we used to be spread into isolated groups, that's why different populations have specificities (e.g. skin colour, but also other adaptations). Now that we have such a huge and interconnected population diversity will fade and adaptation will slow.

I'm not so sure. Even with modern transportation technologies, the price of moving is still high enough that the number of single ethnicity births will generally outpace multi-ethnicity births. I don't think we have nearly enough airplanes and jet fuel to homogenize the genetics of ~8 billion people. But I also haven't run those numbers so feel free to change my mind.

Visit Brazil, they did it with boats.
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