1) Be nice and; have fun
Doxxing, trolling, sealioning, racism, toxicity and dog-whistling are not welcomed in AskLemmy. Remember what your mother said: if you can't say something nice, don't say anything at all. In addition, the site-wide Lemmy.world terms of service also apply here. Please familiarize yourself with them
2) All posts must end with a '?'
This is sort of like Jeopardy. Please phrase all post titles in the form of a proper question ending with ?
3) No spam
Please do not flood the community with nonsense. Actual suspected spammers will be banned on site. No astroturfing.
4) NSFW is okay, within reason
Just remember to tag posts with either a content warning or a [NSFW] tag. Overtly sexual posts are not allowed, please direct them to either !asklemmyafterdark@lemmy.world or !asklemmynsfw@lemmynsfw.com.
NSFW comments should be restricted to posts tagged [NSFW].
5) This is not a support community.
It is not a place for 'how do I?', type questions.
If you have any questions regarding the site itself or would like to report a community, please direct them to Lemmy.world Support or email info@lemmy.world. For other questions check our partnered communities list, or use the search function.
6) No US Politics.
Please don't post about current US Politics. If you need to do this, try !politicaldiscussion@lemmy.world or !uspolitics@lemmy.world
7) No Hit-and-Run questions.
Please don't delete your post for no apparent reason. If you plan on deleting a question later, say so in the post, or if you feel that you have a good reason to remove it, message a mod beforehand. It's not fair to the ones who took their time to answer, and it's not in the spirit of the community.
8) No Bots.
Posts or comments from bots, LLM's, AIs, Neural Networks, Transformers, or Marvin the Paranoid Android are not welcome in AskLemmy. Real humans only please.
Reminder: The terms of service apply here too.
Logo design credit goes to: tubbadu
The current consensus is that the minimum viable population for most species is between 500 to 1,000 individuals.
The problem isn’t inbreeding depression (you only need about 50 individuals to avoid that)—it’s lack of diversity to adapt to a changing environment. Pathogens would evolve that would wipe out the entire species because they’re too genetically homogeneous.
Yup. 500 is a better number as a minimum, but 120 is to small.
https://scicentric.org/minimum-viable-population-humans
Also this kind of happened already
https://www.thecollector.com/mount-toba-supervolcano-wipe-out-humans/
I saw an episode of Nova years ago where dna analysis showed as few as 70 people crossed the Bering land bridge and formed the basis of all Native Americans.
https://www.livescience.com/289-north-america-settled-70-people-study-concludes.html
Now they're pretty sure that people used boats and skirted the coastline but didn't walk.
This is a great video about human migration to the Americas https://youtu.be/UsnrdCdGs7o
That article's over 20 years old—I'm not up on the latest findings, but I know there's been major work since then on both the peopling of the Americas and on the importance of genetic diversity.
It's the other way around. It was once believed that a population of hundreds were needed but the DNA evidence proved it to be much smaller. If you have newer information that shows the DNA work done was wrong, please post it because I've been pulling out this trivia for years.
https://en.wikipedia.org/wiki/Genetic_history_of_the_Indigenous_peoples_of_the_Americas
Don't know about the DNA but White Sands Footprints were dated over 20,000 years old, someone arrived before land bridge was available.
General rule in wildlife biology 50/500. Need 50 individuals to prevent extinction, 500 to have potential to evolve/survive threats.
Here are a couple papers that say those numbers are too low but I don't have access to free copies. Second one a little beyond my understanding.
https://www.sciencedirect.com/science/article/abs/pii/S0006320713004576?via=ihub
https://www.sciencedirect.com/science/article/abs/pii/S0006320706002126?via=ihub
Hmm... the only cited sources in that article for a specific (effective) population size are also over 20 years old—the more recent sources just say it was likely a “small” number.
This article has a lot more detail on the various migration theories, but refrains from any specific size estimates:
the only cited sources in that article for a specific (effective) population size are also over 20 years
When research is old without being found wrong, it is more likely to be correct.
Lots of truth to that but not a lot of grant money available for replication research. After initial peer review might not get revisited for a long time.
Along with other bottlenecks once thought to be humans on the brink of extinction, like with the Toba eruption, further research tends to find other evidence to reverse the extreme nature speculated on. We do on the other hand have evidence of other species that had bottlenecks caused from disasters and the genetic signs are very obvious. Cheetahs as an example.
As few as... likely meant anywhere from 70 to 7000. The ranges on such predictions are usually very wide. Also, sure, 70 people could get lucky and not get wiped out. But the odds are strongly against them.
Even if we started with as genetically diverse set of 120 people as we could manage?
I can’t remember where I read this, but if carefully managed, humanity, in a highly controlled environment, could start off with as little as around 36 individuals. But population and reproduction would have to be highly controlled for dozens of generations before we could breed freely. this is all purely from a genetic standpoint.
And, of course, we would have to be in an environment where we wouldn’t worry about food or pathogens or predators, or anything else that might be a threat to our survival— including each other, or, possibly, ourselves.
The comment you were responding to is estimating a necessary population that takes into account a lot of other environmental factors.
All Native Americans were decended from a population of 70 that crossed the Bering land bridge.
https://www.livescience.com/289-north-america-settled-70-people-study-concludes.html
You're going to need more diversity than just genetic. With that few people, you're going to need doctors, mechanics, scientists, farmers, people with knowledge that can help the colony prosper and prevent what we thinknof as easily prevented diseases and injuries and illnesses.
For example, there's a pretty good percentage of potentially fatal issues during childbirth. Just a few of those and you're greatly impacting your genetic diversity. Immunizations and medicine needs all sorts of production facilities and raw materials, so it's not just "maybe a doc can help me not die giving birth or at least let me try again." Sure, we're animals that can handle some of that naturally, but with that slim of a margin, it's going to be impactful.
If you cherry picked you'd likely be fine.
I think that number is just for a guaranteed successful outcome. Aboriginal people migrated to Australia with maybe as few as a few dozen
Although we're pretty damn adaptable already. If we go extinct, it won't be because we just can't handle a slightly different environment, like a bird or plant. We're tropical apes that have long thrived on fucking sea ice in houses made of snow.
Ok but humans are the literal most adaptable species ever
Humanity started growing massively when the Industrial Revolution hit:
Source: https://ourworldindata.org/population-growth-over-time
So, that would be a factor, whether they'd still have access to technology (and whether we'd expect them to be able to maintain at least some of this technology).
From the aspect of starting over with the existing world, we've depleted most of the much easier resources we had to work with the first time around, so the second climb up technology's ladder would be far harder, maybe even impossible. Reuse and salvage is one route we would take, but some materials can't be. Either they can't be recycled or reclaimed, or like some alloys we've made can't be just melted down and reused, some even can't be reshaped. So many things require an existing and running infrastructure to just make these things.
The first episode of James Burke's Connections series touches on this. Things we don't even think about that support civilization because we've built up around them for centuries, and a lot of it in the most recent century. Starting from base level is far more difficult than the first time around... and like I said, before we had much different resources around us to support the growth.
Depends which 120
If it's 120 men, well, it's going to take a while.
It's fun to stay at the...
From a population of about 1300 individuals, it took 900,000 years to grow to todays 8 billion, theoretically.
from 120 people? You wouldnt have a viable genetic diversity for long term survival. inbreeding would quickly become a thing, and i doubt you'd make it to even 100,000 before total collapse.
For long term survivability, you'd need like..a minimum of 5000 people, and even with 5k you'd have to have strict controls on who could have children with who, for decently long time.
If they don't make it worse with whatever class system they develop, 120 won't be fatal (at a population level). There's groups that exist with fewer, like Pitcairn islanders, who descend from a shipwreck.
It all comes down to how bad an individual person's bottleneck is. The Habsburgs managed to get it down to a single digit number of great-great-great-... grandparents before they went extinct, IIRC.
You never would. You picked all males.
If we give them optimal conditions and the sole purpose of multiplying, it'd still take at least 400 years. 8 billion is a big number, but once it gets going, they multiply fast
It's an interesting idea, because it shows that the crazy ideas that Hitler had about breeding would not work. All the people outside the experiment would easily outbreed them, simply because there's more to begin with.
The same for populating Mars by breeding. Not going to happen. Earth could easily outnumber the Martians by sending a single ship in that timeframe. Whatever purpose colonizing Mars has, it'd be a waste of time trying to breed humans there.
Same thing for the fearmongering about Muslims outbreeding the European populations. Not happening. Whatever cultural differences we have today will be far gone by the time that the genetics of either group outbreed the other. It's like complaining about half the current population being descendants of Ghengis Khan. It makes no difference.
Um... 400 years is rather low. Even for optimal. But realistic is more like 1000's.
Hitlers idea was to keep killing the people with the wrong genetics for as long as it took. Hand him nukes and he could clear people a lot faster at the cost of getting some of those he wanted to keep. I bet he would have been willing to trade.
Mars... no idea what you are talking about. No one has ever suggested mars could outbreed earth.
Muslims... the fearmongering I hear is that they will pollute the culture by bringing their own. Don't need to outbreed for that. And mixing of cultures is a good thing, not a bad one. That is the real reason those people are wrong.
For most of history, people were dying of bullshit about as fast as they were made, especially the kids. OP didn't specify if that comes back, and a few hundred is what a premodern birth rate gives you without it. Relatedly, 15% of everyone who's ever lived is still alive, because growth has been so fast since we figured out how to stop, like, plagues.
Well: if we believe Christianity we only needed 6k-10k years from two people to the billions we have today, so it shouldn’t take so long
It depends massively on birth rate. If it stays the same, never, we die out shortly. If it goes back up to a (conservative) premodern 5 children per woman, with the same negligible early death rate, log~5~(8,000,000,000/120)=~11 generations. Rounding up and assuming 25 years per generation, that's 300 years. Also genetic diversity isn't as good and there's more genetic illnesses.
Anything in between is possible. Child and some adult mortality meant premodern populations grew very slowly, on the order of some percentage per century, so that's an option. Then it's basically whenever they advance to a 19th century level. If they manage to save and use the frozen sperm samples that exist, the genetic diversity issue could also be avoided.
Assuming the 120 people have access to existing world history I'd hope they manage to arrange things such that they never get into that kind of trouble.
Some years ago I'd have thought the same but today I'm sure there would be at least one person that exploits others to gain even a small advantage. In the end we'd be back where we are today.
It would give a serial killer a real shot at ending the cycle
Like malaria
I think she spells it “Melania.”
I don’t know that 120 people offers enough genetic diversity for a species to thrive. The population would, the way I see it, increase for a while and then start to collapse.
7000 years.
But 120 people means: zero division of labor, zero technology, only stone age and all are generalists.
Can you explain how you get to that number? Assuming how many surviving kids and how long til they reproduce again?
this is just the plot of the 100; it didn't go well.
Do they all start in the same area? Or are they spread out across the globe?
Depending on the 120 people. Most of these people are still in the primitive ages with tech and science so they will talk about genetics not knowing shit.
We won't.
Way too inbred