Mysterious ‘super-archaic’ populations had multiple trysts with human ancestors
sciencemag.org
sciencemag.org
> 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 densely spread species with … so little genetic diversity … is a dangerous situation,” she says.
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 diversity. Even just the number of easily observable environmental adaptions present in populations are countless (Sherpa, Bajau people, etc.)
As for COVID-19, most people are more-or-less unaffected by it. Our genetic diversity is working as intended.
Also, we don't know that most people are more or less unaffected by covid-19. We're only beginning to understand long term affects of even mild cases. Please don't spread misinformation.
So, like 1918 pandemic flu?
covid19 and the Spanish flu are not even in the same weight class, not even a little bit, whereas yes, like it or not, covid19 is most likely in the same weight class as the flu depending on your thresholds with the flu at .1% and CV19 around .5 to 1% (likely closer to .5%).
yes, there are some people with long term effects of cv19. that's also true of the flu. Many scientists think age related dementia is caused by repeated exposures to the flu/cold. flu/cold have also caused heart and organ damage to many, it just doesn't get reported on. 'oh, this person died of organ failure, wonder why'. It's already a proven fact that the flu has caused the onset of type 1 diabetes for example. There are also many reported cases of heart disease caused by the flu. the flu sucks.
people loose their sh*t when you talk about this. it doesn't minimize the effect of covid19, it just highlights the flu is something serious. for some reason, people are too immature to handle that. or maybe it goes against their worldview we should burn the world to the ground in order to stop covid19.
My understanding, however, is that the transmissibility of covid-19 is 3 to 10 times greater than the common flu. For instance, our local public transit agency doesn't have dozens of drivers testing positive for the flu and having symptoms each year. Coupled with the, something between 2 and 10 times greater death rate, the largest concern is overrunning hospitals if there is a bad wave in an area. As another example, because it's more transmissible, my community is also worried about getting infected because don't want to infect family if we get it, whereas I don't think we worry about the same with the flu.
My understanding of the current situation is that if everyone would wear a mask and social distance, there would be very little reason to continue with many of the other precautions that have been instituted. As you said, we live with the flu, so we don't need to make the transmissibility 0.
I'm going to be very interested to look back at this in a decade and see what we've learned and what could have been differently. How overblown, or conversely, how valid are our fears right now? The biggest problem is we just don't know, and won't for a while.
It looks like our protections for Covid-19 were very effective against Flu transmission at least that is the assumption.
Also, these are the numbers for CV19 given unprecedented social distancing measures, entire hospitals dedicated to it, border closures and so on. If nothing had been done, it seems likely, given regional examples like Italy's Bergamo area, the death rate could easily be 10 times what is observed today, if not more.
Equally, with much stronger and more targeted measures, the death and infection rate can be brought to essentially 0 without impacting the whole population as much, as shown by Vietnam.
It is still absurd to call a disease that has already killed many more people than malaria this year 'similar to the flu'. Sure, the flu is bad, but in conservative estimates, Covid19 is 5 times worse (and in more equal comparisons, where we would take similar measures to what we do for flu, it is probably more than 100 times worse).
It also didnt help that our health system was killing covid19 patients by giving putting them too aggressively on respirators. it's an inconvenient truth you get shouted at for bringing up.
Even with these absurd metrics for mortality, its clocking in at .3%. So in my opinion, its in the same weight class as the flu, but if you have such a problem with it, that's why I qualified the statement as I said it, depending on what your threshold is.
Keep in mind, the flu at the end of 2019 going into 2020 was a particularly bad flu. the mortality rate of those going to the hospital was around 6% according to the CDC.
it would not be 100 times worse than the flu. we have so much data on covid19 now, and nothing has really changed since the cruise ships, which was basically a free experiment for the world that has been promptly ignored over and over.
By the way, here's evidence that the Spanish Flu had a 20% death rate: https://www.smithsonianmag.com/history/ten-myths-about-1918-...
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 got tinnitus in my right ear and pain when ejaculating.
None of this has ever happened with any flu or cold that I ever got.
Uh, thanks for warning, I guess? (nervously adjusting my FFP2 mask)
I am aware it sometimes tells you nothing at all.
> We're only beginning to understand long term affects of even mild cases. Please don't spread misinformation.
Asymptomatic cases are not the same as mild cases.
Besides, always assuming the worst-case scenario, especially when all previous experience tells us to be optimistic, is not a workable strategy.
That's one definition of "species" (specifically, it's "the biological species concept"), but like all the other definitions, it doesn't work and does not correspond to most usage of the term. You can read modern genetic work discussing how homo sapiens interbred with hominids of other species. 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 objectively useless for anything but naming things. You might as well use a random name generator, draw lines in the sand in geometrically pleasing ways, and pretend it's a "system".
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.
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?
Taxonomy, a specialization of biology, is the study of how organisms can be usefully classified. A major aspect of that study is the determination of how species are categorized, and how ancestral relationships are recognized. When this is done through molecular phylogeny (ie direct analysis of genetic relatedness and ancestry), the result is a directed graph called a "phylogenetic tree", whose nodes denote species and whose edges denote descent. Such a tree is called "monophyletic", meaning that it contains both, and only, a specific common ancestor and all descendants of that ancestor. Any subgraph from a single node of a monophyletic tree is also monophyletic. In this way, it's possible to establish a relatively unambiguous understanding of descent and relatedness among possibly widely varying organisms.
There are other kinds of classification which often produce groupings that make an intuitive kind of sense in terms of similar characteristics and the like, but which don't accurately represent relatedness. The Linnaean taxonomy is one of these, and the two terms used in cladistics to describe its categories of error are "paraphyly" and "polyphyly".
A paraphyletic grouping is one which contains a single common ancestor, but fails to contain all of its descendants. Many hymenopteran families are like this, such as Crabronidae, which is "all Apoidea that aren't bees" - bees and ants being actually descended from basal wasps, which were themselves descended from an even more basal shared ancestor with modern sawflies. Paraphyletic groupings can be useful, but aren't to be relied upon to accurately describe descent, and are replaced with monophyletic groupings as the necessary research and analysis is performed.
A polyphyletic grouping is one which fails to contain a common ancestor. For example, the European paper wasp (P. dominula) and the eastern yellowjacket (V. maculifrons) closely resemble one another in size, body shape, markings, and much behavior. Based on that, a Linnaean taxonomist might classify them as separate species within a single genus. This (hypothetical) genus would be polyphyletic; while these two wasps are indeed closely related, they're not that closely related, sharing a common ancestor with several other genera including all other social wasps and a sizable fraction of solitary species.
How exactly this all relates to the concept of "species" is hard to really define, at least for me as an amateur, but I think maybe also for professionals in the field. The classical definition, that a species consists of all individuals able to interbreed and produce fertile offspring, and none which cannot, fails to explain cases like wolves and coyotes, lions and tigers, or horses and donkeys - all pairs which are classified as separate species, but nonetheless are able to produce fertile offspring at least some of the time. Phylogenetics offers a distinct species concept [1], defining a species in terms of interrelatedness and innovation in traits as compared with ancestors - I suppose the classical definition could be called "horizontal", while the phylogenetic one could be called "vertical". Notably, the phylogenetic species concept appears to place no significance on interfertility or the lack thereof, which would mean that Equus, Canis, and Felis are not necessarily paraphyletic at all - they might be, but that wouldn't be defined on the basis of interfertility.
In the limiting case, I suppose that means each individual organism could be considered to constitute a unique species, although that is probably nonsense and certainly too granular to be useful. In any case, I hope all this answers your question, and provides some ground for further study. I've certainly learned something today, just looking up references! Thanks for the impetus to further systematize my understanding of the subject.
[1] https://www.oxfordreference.com/view/10.1093/oi/authority.20...
Categories are hard.
I guess it's kind of a temporal ring species.
(Also note that while it's perfectly possible to walk up from humans to an ancestral slime creature, and then back down to dogs, most of the steps along that path will be shared between humans and dogs, like a Y with a very, very long leg. The recent common ancestor of humans and dogs would have already been a mammal.)
In principle you even could have some kind of genetic helix, where one end of the ring species not only meets but overlaps with the other, perhaps going so far as to do a full wraparound a number of times. But probably the two ends of the ring would occupy too similar an ecological niche (even with all the genetic divergence) to allow for much time of overlap.
"Can reproduce with" is not a transitive (or even a permanent!) property among individual humans. (For a more general transitivity allowing for the fact that it doesn't make sense to ask whether males can reproduce with males.)
Since they were purged and exist as remnants in individuals' DNA.
(1) https://www.scientificamerican.com/article/humans-are-all-mo...
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...
Now that we have such a huge and interconnected population diversity will fade and adaptation will slow.
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.
The last X is an easy target.
on edit: for anyone unfamiliar with this trope, see https://en.wikipedia.org/wiki/Requiem_for_Methuselah or https://en.wikipedia.org/wiki/The_Man_from_Earth (both written by Jerome Bixby, but many other examples by Neil Gaiman, etc. available) for easy clarification. One of the common ideas of the trope is that an immortal sooner or later becomes problematic to have in one place, they must wander of people will attempt to experiment on them to figure out the secret of immortality. Of course the second bit of the trope is the wandering immortal leave traces, and more intense searchers after immortality will follow them and attempt capture. If diversity decreases in the future based on present trends the story then becomes that it becomes increasingly difficult for the wandering immortal to wander without everyone being aware of them.
Sometimes without the trope you mention (L. Sprague de Kamp's The Gnarly Man[0])
And sometimes with a variation on it (Heinlein's Methuselah's Children[1]), which he follows up with some of the same characters, but not invoking the trope (Time Enough for Love[2]).
There are many others of course, those are just the ones that came off the top of my head.
[0] https://en.wikipedia.org/wiki/The_Gnarly_Man
Geographic variation will not dissappear completely, but the granularity and amplitude of those variations was and will continue to be smoothed a lot.
All in all, the global human population will become more homogeneous and less diverse.
https://news.sky.com/story/human-microevolution-sees-more-pe...
Speciation processes may return once we start colonising other planets as it is highly possible that physical contacts between populations will stop.
I know it's macabre, but I think about human migratory routines and when different groups clashed back when life was so primitive and brutish, they're must've been those tendencies to rape and sexually conquer the opposition.
Surely that is reflected in the genetic ledger of time. What a crazy insight. Genetics is such an interesting field. It's bonkers there's just strings of data that we can read the past through.
I think at some point in the far past though there might have been a wider gap, genetically, between the two forces meeting. I haven't had time to read the whole article in detail, just skimmed it.
Anyhow, thanks. You're right, there's definitely been plenty of mandatory diversification before.
2. John does not rape.
3. Therefore, John is not a mammal.
2. John does not rape
3. ∴ John is not the raping member of a Species of Mammals
Pardon any misuse of symbols, it's been a while.
Even seeming straight forward metrics like "can they produce viable offspring" isn't so black and white, since between 'yes' and 'no' exists a continuum of 'maybe's. In very rare cases even horses and donkeys can have fertile offspring, e.g. mules that aren't mules (the typical infertility of mules has lead to the occasional use of the term to describe any infertile hybrid.)
https://www.smithsonianmag.com/science-nature/colored-pigmen...
https://en.wikipedia.org/wiki/Earliest_findings_for_hominid_...
There was inevitably conflict, but I'm skeptical of the "tendencies to rape and sexually conquer the opposition" framing. AFAIK there isn't much evidence for large amounts of inter-group violence. A paper like https://onlinelibrary.wiley.com/doi/full/10.1002/ajpa.23751 lays out a contra case that the absence of evidence isn't evidence of absence--but I think it is a reason to be cautious about what we project back on those populations.
It’s full of “and then tribe X invaded and the land of Y, took their women and enslaved their men”. Back and forth for centuries. This behavior was cyclical, inevitable, and universal, until violence was monopolized and institutionalized.
We’ve come a long way, I guess. Still have work to do.
From what I understand, the most common view is that in hunter-gatherer times there was much less inter-group violence than there was after the advent of agriculture, simply because there was much less of a notion of territory and any need to defend it before agriculture was a thing.
Do you mean the Bible?
"Only in the cities of these peoples that the LORD your God is giving you as an inheritance, you shall not leave alive anything that breathes. But you shall utterly destroy them, the Hittite and the Amorite, the Canaanite and the Perizzite, the Hivite and the Jebusite, as the LORD your God has commanded you,...? Deut. 20:16..
I was thinking actually quite a bit earlier than a lot of the Hebrew historical times, like species that were more apelike.
https://history.stackexchange.com/questions/23975/what-was-t...
Why couldn't they have been meaningful relationships?
I think it's most interesting to think of how fluid what we mean by species really is. We've always known it was fluid, but I think many people never really consider that when thinking about ourselves.
The act of separation would create new species. Not our drive to bone.
VOY 3x23 Distant Origin [2] also in-universe establishes convergent evolution is very likely to create humanoids (makes no reference to the other two episodes, as far as I remember, but it's kinda wishy-washy in that it could be highly likely because of the two progenitor species).
That said, there's plenty of non-humanoid aliens. Off the top of my head: Q, the Tholians, the Caretaker's species, the two aliens from TOS 2x01 Catspaw (shown to be tiny and kinda birdlike in the final scenes), and Species 8472.
[0] https://memory-alpha.fandom.com/wiki/Return_to_Tomorrow_(epi...
[1] https://memory-alpha.fandom.com/wiki/The_Chase_(episode)
[2] https://memory-alpha.fandom.com/wiki/Distant_Origin_(episode...
I kid; I know you said "at least".
[0]https://memory-alpha.fandom.com/wiki/Unexpected_(episode)
(Though I admit that the ENT example was certainly unique in the differing biologies)
Sometimes real constraints (eg costuming/budgets/etc) can result in really clever explanations that strengthen the storytelling/worldbuilding.
I'd say that for most Sci-Fi Movies/TV there's a couple of reasons:
1. Non-humanoids are less relatable than humanoids;
2. Budgetary restrictions and the relative immaturity of CGI holds us back from creating fairly realistic and relatable alien species.
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 about the genetic isopoint [1], which is the most recent time when every human alive then was either an ancestor of every human currently alive or had no descendants that are currently alive.
Most researchers put the genetic isopoint somewhere between about 4000-15000 years ago.
If both of these are true (or even if not, as long as the genetic isopoint is after Neanderthal extinction), then all my ancestors that descended from Neanderthals and were alive at the genetic isopoint are also your ancestors, and so you are also descended from Neanderthals through them.
There seems to be a lot more uncertainty about when the Denisovans went extinct. It seems likely that they were probably also all gone by the isopoint and so "all" rather than "many" probably goes for them too.
Your kids only get half your DNA, their kids only get half their DNA, and so on. You can eventually end up with descendants who have none of your DNA.
If the genetic isopoint really was after the Neanderthals went extinct than everyone in sub Saharan Africa has Neanderthal ancestry even if none of them have Neanderthal admixture.
> ...which involves only three expansions of humans from Africa into Eurasia: an expansion of early Homo at about 1.9 Ma ago, an expansion of neandersovans at about 700 ka ago, and an expansion of modern humans at about 50 ka ago.
The “early Homo” or “superarchaics” are H. erectus and their DNA contribution is inferred since no sequences have yet been extracted. “Neandersovans” is the common ancestor of European Neanderthals and Asian Denisovans.
Interbreeding occurred in Eurasia after the second and third expansion.