Was reading up about mammoths in the Arctic Circle and it said once you dip below a certain number the species is doomed.
Why is that? Couldn’t a breeding pair replace the herd given the right circumstances?
Was reading up about mammoths in the Arctic Circle and it said once you dip below a certain number the species is doomed.
Why is that? Couldn’t a breeding pair replace the herd given the right circumstances?
Comments
Inbreeding would cause many birth defects over time and prevent said population from surviving long term.
When a population size falls below a certain threshold, the genetic pool becomes too restricted for a number of things that are essential for species to survive.
A couple of examples of this would be:
– it makes inbreeding (and the illnesses that come from that) a certainty.
– Any genetic disease hit every newborn (think sickle cell, huntington’s, etc.)
– any vulnerability to infectious disease will mean that a single infection wipes every individual out
Technically they could, but a low genetic diversity usually ends in an entire population susceptible to the same diseases or can’t really adapt. So if there is a new virus/bacteria, it gets a little warmer, or oxygen levels dip for example, they’re all going to die.
When you have a bigger population, there is more genetic diversity, and usually SOME individuals can adapt to the new condition, survive and continue breeding.
You need a minimum number of fertile individuals to provide enough diversity in the gene pool to prevent decline due to inbreeding, infertility, death before sexual maturity, etc.
Inbreeding is well known to produce a lot of problems, which is why pretty much all cultures frown on incest.
Another problem is a lack of genetic diversity to deal with new problems. A disease hits and with a lot of diverse genes there might be some individuals who are better able to cope and survive. But if all the individuals have the exact same genes then a disease that kills one will likely kill all.
It’s not 100% impossible for a species to survive from a single breeding pair, it’s just so unlikely that below a certain threshold researchers basically consider it a lost cause. A single accident, a single season of harsh weather, a single disease or genetic defect could easily wipe out a too small population. You need numbers to reliably survive those things (even then it’s all probability, a huge disaster could still wipe out a big population).
im not a scientist but I imagine that external threats (predators, disease, force majeur) far outweigh a simple breeding pair. It might take years for a single offspring to reach sexual maturity to even breed and in order to do so, they need to survive long enough to do it.
it probably comes down to a numbers game too- if an animal say a woolly mammoth can only have 1 offspring at a time, and then that child gets preyed upon, then theres gonna be fewer chances for a new generation to emerge. contrast that to animals with a high ability to produce multiple offspring (also known as fecundity) like mice, they win the game by just have a crap ton of kids to outweigh the external threats (as far as numbers go). its more likely that they will survive to breed a new generation just due to sheer volume
Gene pool too small. You get inbreeding and shit gets fucky.
Mutations that are hereditary and kill off offspring before they mate will bring about the eventual demise of the species. And even if they do mate the gene pool is still going to be shallow and the next generation may not be so lucky.
And that assumes the remaining population are able to find each other and mate and then have enough resources to keep going. Lots of ways the species can go extinct and a much smaller window to keep going.
Because you have to breed fast enough to produce more kids that can produce more kids. And inbreeding can become a problem.
And in areas where competition is fierce and not all children make it to puberty maintaining a breeding population is that much harder. Each breeding pair has to produce three kids (that make it to breeding age, yes the number can be a fraction but this is ELI5) in order for the population to grow and if you lose some number of the kids to disease, predation, lack of food, suddenly your have to have four, five or six kids in order to have those three that make it to breeding age.
Look at WHY you dipped below a certain number. That explains why you can’t carry on.
You need four things to continue a species.
First, kids.
Second, ability to feed the kids until they grow up enough to have other kids. That takes a lot of resources.
Third, other stuff not interfering with your kids having kids, and their kids having kids, and THEIR kids having kids, and so on. That means there aren’t poisons, or hunters with guns, or enough local prey animals getting eaten by someone else like humans, or some new suburb’s construction or coffee plantation not killing the trees you depend on, or agriculture killing the local land plants for a crop…
…All of these can destroy your chances of another generation.
Fourth, luck.
The problem with small populations is they need stable conditions to recover. Humans rarely provide them outside of captivity.
Small populations and even single breeding pairs absolutely are not doomed to extinction. They are just more likely to go extinct. There are plenty of well documented cases of populations coming from a single pair
I hope you’re not asking this question in earnest. Otherwise, I hope there’s an actual subreddit called “r/explainBECAUSEImfive”
NO human past age seven should not know the answer to this question. I’m being generous, considering how educated kids USED to be.
If you were raised believing in a human breeding pair being the progenitors of our species, the science of the last two hundred years is about to slap you across the face. With it’s enormous, flaccid penis. Not a gentlemanly slap of the palm. Worse, there’s no retaliating against the gigantic mushroom stamp of truth that is hard science. You just have to take it.
Notwithstanding the biblical population bottleneck of the Flood (not to be mistaken with the Flood in Halo, which is a vastly more likely scenario). THAT postulates all of humanity not only originates from two humans, but that evolution was allowed to take place for ALL animals; but that only a certain amount survived a PHYSICALLY IMPOSSIBLE
catastrophe (there isn’t enough water to flood everything), and that ALL humans are derived from a man, his wife, their three sons, and those sons’ wives. So, eight people.
Again, that’s EIGHT PEOPLE. SOME PEOPLE BELIEVE ALL HUMANS ARE DESCENDED FROM EIGHT HUMANS, LESS THAN FOUR THOUSAND YEARS AGO.
In addition to what everyone else is saying: generally speaking, a species goes extinct because their environment has changed in such a way that they no longer have a place in the ecosystem they can thrive in.
If your species is in a downward trajectory, it is for a reason. If that reason never goes away, you are generally going to continue on that downward trajectory until extinction.
This isn’t a universal truth and there are a myriad of exceptions, but it is the general rule.
We can see this in humans populations, like small villages where people keep marrying inside the village until pretty much the entire village is family.
“High prevalence of infant mortality is associated with high rates of consanguineous marriages”
Consanguine marriage is marriage between individuals who are closely related.
The descendants of that breeding pair would all be siblings.