Questions about population bottlenecks

The TGC article references that geneticists believe that the population has never been below 10k in a matter of fact kind of way…can someone explain why so definitive?

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See here: Heliocentric Certainty Against a Bottleneck of Two?

And here:

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So, I’ve read through those and Buggs stuff here: Adam and Eve: a tested hypothesis? | Nature Research Ecology & Evolution Community

I am not understanding the simplest of questions…Popular opinion is that there were 10,000 Adam and Eves? Set aside bible opinion for now, use Adam and Eve to mean first humans…the argument is that we started with 10k? So, where are the Ancient Alien proponents in the discussion?

From my lay-person understanding, DNA changes after breeding, but in-breeding leaves a marker. To suggest that population never dips under 10k assumes that you know where the DNA started… the first sample, or rather that you know the first 5k sets, right? Baseline DNA that proves the point…From a non-scientist standpoint, I would say someone is missing something important. How then did we get to 10k from 0 is the obvious question…

Where they should be, absent. Hopefully.

There was never a time at which the ancestral population we all derive from was 0, unless you mean 4 billion years ago (or thereabout). That is to say, before the origin of life. Humans evolved from non-human ancestors, which also had population sizes greater than 0. These in turn evolved from even more distant ancestors. And so on, all the way back to the very origin of life on Earth.

You might mean to say, instead, that there was presumably some point at which no humans were in existence, but our non-human ancestors were. In that sense yes, of course, the size of the human population was 0, because humans had not yet evolved.
However you define human(which would always have to be arbitrarily), at some point, someone would get born who would satisfy that definition and constitute the first human, which would mark the point at which the human population went from 0 to 1 individuals(unless it was twins, in which case it jumped straight to 2).
This one(or more) individuals would go on to grow up and have offspring of their own, which would mingle and interbreed with others in that (still almost entirely non-human) population, leaving children who possibly also would meet the definition of human due to having inherited those human-defining attributes whatever you think they are. And so on and so forth.

So when popular scientific opinion states that the human population has not dropped below 10k, this includes non-humans?

How can it be said with certainty, if human/non-human is not clear?

I guess what bothers me is that it is a statement not a question. Should be open for discussion, seems like a “the world is definitely flat” discussion. The philosophy of never below 10k suggests POOF here we are, like creation, or like something is missing in the explanation.

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You’re missing a large part of the discussion. Extant humans have an unbroken string of ancestors going back almost 4 billion years. That includes the last 4-6 million years of our ancestors being now extinct hominids. The place on that unbroken string where we became anatomically modern humans (AMH) is defined as around 200 thousand years ago. In the last 200 thousand years the population in that time has never dropped below 10,000 breeding pairs. There was never a time when there were 0 extant human ancestors. The idea there were 0 humans before 200K years ago is due to our chosen definition of where AMH started.

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Can you explain why in relatively simple terms?

For most of that time the population was much larger, several hundred thousand individuals at least. Genetic evidence shows humans and several other large species suffered a population bottleneck between 70,000 - 80,000 years ago. This happens to coincide with a supervolcano eruption at Toba, Indonesia 74,000 years ago. The severe environmental disruption is thought to have caused a “nuclear winter” lasting at least 5-10 years which drastically reduced the population possible to as little as 20,000 individuals. It is hypothesize this volcano was the cause of the genetic bottleneck although the case is not clear by any means.

Toba catastrophe theory

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The question is open for discussion, and the evidence in that discussion is modern human genetic diversity. Put quite simply, there had to be a continuous population that never dipped below tens of thousands of individuals over the last ~200,000 years in order for there to be as much genetic diversity as we see in today’s human population. A good counterexample is the cheetah where the population has very little genetic diversity due to a bottleneck of perhaps just a handful of individuals.

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None here at PS, so far, but they exist. My only encounter was one guy on Facebook, and I really hope he is not representative of the group.

I hadn’t seen that symbol before. It would seem to imply that Raelians are Jewish Nazis. Odd.

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That Raelian logo has certainly got them a lot of criticism for that reason. I had understood that they had created a revised logo that eliminated the swastika but it appears that both the old and new design are in use, depending on the area of the world.

It is also worth emphasizing what most readers here probably already know: the swastika is a very ancient symbol and it remains popular even today in many Hindu and Bhuddist countries as a representation of good luck and prosperity. (If I recall correctly, the word swastika is an ancient Sanskrit word referring to anything which promotes well being.)

The sticking point for the Ancient Alien folks is explaining how a separate alien species that evolved on a different planet could somehow have DNA that is 98% the same as chimp DNA. Not only that, but the aliens would need to have the same DNA markers, such as 200,000 identical retroviral insertions to those found in the chimp genome. If humans are the descendants of acient aliens then our genomes should be completely different from any other species on Earth, but they aren’t.

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That is quite an understatement.

Its the Indian Swastika… Its a very Old symbol used in Hinduism and related religions.

By your logic, ancient Indians were Nazis.

Ancient Indians used the symbol prior the Nazis, Raëlians used it after, while fully aware of the all baggage it holds in modern times, particularly in the West.

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The Nazis used a different orientation of the symbol (It was rotated by 45 degrees in the Nazi Symbol).
The one the Raelians are using is the exact same as the Hindu symbol.
It would be helpful if the “west” educated itself a little more.

Do you think most people are particularly bothered by orientation when they see a swastika and the Star of David together? Remember, John’s point was just that the symbol was an odd choice at best, not that Raelians are actually Nazis.

It doesn’t make any difference. They ended up in trouble for having a “Nazi” symbol in the west. Even had to change the symbol… (till 2007 atleast).
Basically Hitler co-opted an ancient symbol 50 years ago and suddenly it belongs to the Nazis, even though it has been used for millennia in India, china etc.
That’s what is odd.

Do you really find it odd that a symbol featured prominently by a fascist regime that instigated world war 2 and carried out the systematic extermination of millions of innocents, all in living memory, is more present in the minds of Westerners than the version with a slightly different orientation that predated it In Asia?

No one is saying the swastika “belongs” the Nazis now, but people shouldn’t be surprised that when westerners see it, their first thought is “nazism” not “ancient Indian symbol”. This reality means that people should think twice about employing the symbol in the west, that’s all.

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