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Humans are more closely related than we commonly think

scientificamerican.com

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Re: Humans are more closely related than we commonly think

#11

Post by pavanky »

samatman wrote: post #6

So I was wondering if this article was just being incredibly misleading or straightforwardly lying, and I hit this: > “If you were alive at the genetic isopoint, then you are the ancestor of either everyone alive today or no one alive today,” Yeah. That's a lie. There's no way around it, this is a dishonest statement. I'm in no kind of mood to explain why that is, for pretty predictable reasons this conversation goes…

This is idiotic.If this was true, Humans wouldnt share 90%+ genetic similarity with great apes (depending on which genes you count) which would go against every scientific consesus.

And you are claiming humans share no genes each other over a span less than 100K years.

Re: Humans are more closely related than we commonly think

#12

Post by tasogare »

samatman wrote: post #6

So I was wondering if this article was just being incredibly misleading or straightforwardly lying, and I hit this: > “If you were alive at the genetic isopoint, then you are the ancestor of either everyone alive today or no one alive today,” Yeah. That's a lie. There's no way around it, this is a dishonest statement. I'm in no kind of mood to explain why that is, for pretty predictable reasons this conversation goes…

Well the most common ancestor is used to push a certain narrative about all people "being the same", while conveniently putting aside hundreds of thousands years of evolution, which are precisely the source of the present day differences, but that doesn’t mean it’s false either, as there is indeed a common ancestor if we look back far enough.

Re: Humans are more closely related than we commonly think

#13

Post by Jaruzel »

samatman wrote: post #6

So I was wondering if this article was just being incredibly misleading or straightforwardly lying, and I hit this: > “If you were alive at the genetic isopoint, then you are the ancestor of either everyone alive today or no one alive today,” Yeah. That's a lie. There's no way around it, this is a dishonest statement. I'm in no kind of mood to explain why that is, for pretty predictable reasons this conversation goes…

Take a deck of cards, and heavily shuffle it. Is it the same deck or an entirely new one?

I think most of us understand that there is a difference between sharing DNA and biological ancestors.

Re: Humans are more closely related than we commonly think

#14

Post by lopmotr »

samatman wrote: post #6

So I was wondering if this article was just being incredibly misleading or straightforwardly lying, and I hit this: > “If you were alive at the genetic isopoint, then you are the ancestor of either everyone alive today or no one alive today,” Yeah. That's a lie. There's no way around it, this is a dishonest statement. I'm in no kind of mood to explain why that is, for pretty predictable reasons this conversation goes…

The statement you're arguing against says nothing about having DNA from that ancestor, just about their existence as an ancestor. Instead, the article seems to agree with you, saying: "Not everyone of European ancestry carries genes passed down by Charlemagne, however. Nor does every Jew carry genes from their Sephardic ancestors expelled from Spain. People are more closely related genealogically than genetically".

Re: Humans are more closely related than we commonly think

#15

Post by andi999 »

lopmotr wrote: post #9

Weren't Australian Aboriginals isolated for tens of thousands of years and some full blooded individuals still exist today? How could they have an ancestor outside Australia in only 1400 BC?

Well, the article talks a lot about 'our ancestry' and not all of mankind. So probably it applies only to 'us'(Europeans and US) and not 'them'. Ok, probably it was just lazy science and no politicsl agenda.

Re: Humans are more closely related than we commonly think

#16

Post by titzer »

samatman wrote: post #6

So I was wondering if this article was just being incredibly misleading or straightforwardly lying, and I hit this: > “If you were alive at the genetic isopoint, then you are the ancestor of either everyone alive today or no one alive today,” Yeah. That's a lie. There's no way around it, this is a dishonest statement. I'm in no kind of mood to explain why that is, for pretty predictable reasons this conversation goes…

Your intuition on this is wrong, and there's no need to fly off the handle.

Ancestry is infectious. Take two populations, A and B, completely isolated from each other. (nevermind that they all have a common ancestor long before the populations diverged). Now one day in 1000 B.C. a single individual from population A migrates over to population B, mates, and has offspring (more than 1) with an individual from population B. Just keeping things simple with 2 children per generation. The next generation, those 2 individuals go off and have offspring with other members of population B. That's 4 descendants. Next generation 8. And so on. Of course the characteristics of population A (it's phenotype) may become less, because proportionally, that individual's genes make up less and less with each generation. So it might not even be detectable by looking at someone that they have a tiny bit of A's genes.

The key is that the propagation of ancestry never stops, because ancestry doesn't round down to zero. It's a mathematical relation. Now, genetically, those genes keep spreading (thinly) over the entire population, generation after generation, so it is actually possible that those genes get rounded down to 0, and you actually have no DNA in common with that ancestor (except that which they had in common with your other ancestors). But mathematically, in terms of ancestry, there is a point many generations later that it becomes almost impossible to not interbreed with someone who is descended from A.

This is exactly the intuition behind this genetic isopoint--when you run the exponentials either direction in time, they overflow the population. So you either have your genes completely selected out, or they "infect" the entire population, assuming that you and your offspring consistently have more than 1 child on average.

Re: Humans are more closely related than we commonly think

#17

Post by JPLeRouzic »

samatman wrote: post #6

So I was wondering if this article was just being incredibly misleading or straightforwardly lying, and I hit this: > “If you were alive at the genetic isopoint, then you are the ancestor of either everyone alive today or no one alive today,” Yeah. That's a lie. There's no way around it, this is a dishonest statement. I'm in no kind of mood to explain why that is, for pretty predictable reasons this conversation goes…

Most of our ancestors, even in recent history have migrated a lot.

For example Vandals, a tribe living in Poland, moved west and south, and established kingdoms on the Iberian Peninsula, Mediterranean islands and North Africa in the 5th century! Many tribes living in Europe had a similar migration pattern at that time [0].

This was a part of humans migrations from Asia to Europe, pushing people ahead of them. Another incredible migration is the Bantu expansion, where people consistently moved eastward and southward for at least a millennia.

And we changed a lot in the process, New arriving people in Europe from Africa, at the end of the ice age, had a much darker skin than today.

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

Re: Humans are more closely related than we commonly think

#18

Post by titzer »

tasogare wrote: post #12
samatman wrote: post #6

So I was wondering if this article was just being incredibly misleading or straightforwardly lying, and I hit this: > “If you were alive at the genetic isopoint, then you are the ancestor of either everyone alive today or no one alive today,” Yeah. That's a lie. There's no way around it, this is a dishonest statement. I'm in no kind of mood to explain why that is, for pretty predictable reasons this conversation goes…

Well the most common ancestor is used to push a certain narrative about all people "being the same", while conveniently putting aside hundreds of thousands years of evolution, which are precisely the source of the present day differences, but that doesn’t mean it’s false either, as there is indeed a common ancestor if we look back far enough.

I think it's clear from history that narrative of us "being the same" hasn't caused nearly as much trouble as the opposite, the complete and utter lie that we are not all human.

Re: Humans are more closely related than we commonly think

#19

Post by jlawson »

themgt wrote: post #3

While this article's content isn't exactly wrong, the Wikipedia on "Identical ancestors point" gives some important context for what's actually being asserted: All living people share exactly the same set of ancestors from this point back, all the way to the very first single-celled organism. However, people will vary widely in how much ancestry and genes they inherit from each ancestor, which will cause them to have…

Another important point here is that genes don't divide infinitely, so that if you go back some distance, you start finding ancestors from whom you actually didn't get any DNA.

The book Who We Are and How We Got Here talks about this. When DNA recombines at conception, it only snips and stitches in a fairly limited number of places. It doesn't 'mix' finely like paint. It's more like taking two short pamphlets of ~25 pages, cutting each numbered page horizontally at a random vertical point, and then assembling a new pamphlet of the original size from each pair of pages (pamphlet A's page from above the cut, pamphlet B's from below).

All this to say that if you go back something like 800 years, you have ancestors from whom you didn't get any genes at all.

This means that these infintesimal mixings have even less impact than you'd think. A modern Japanese person could have a European ancestor who traveled to Asia a thousand years ago, but have zero genes from that ancestor. Which means that while that European is technically an 'ancestor', this is just a bit of historical trivia, it means literally nothing about that Japanese person's biology.

---

On to the color commentary:

I suspect that articles like this are heavily influenced by the politically-based drive to try to minimize intergroup genetic differences in humans. The reality is opposite the title - humans are far more distinct, especially on group levels, than is commonly understood. The notion that single common ancestors (among trillions) mean people from hugely divergent groups are 'related' in some meaningful way is just exploiting and expanding the ignorance of the public around how genetics actually work.

It's arguably a pro-social thing to do; I'd say I agree with the philosophy here, but that doesn't make it true and the 'noble lie' seems anything but to me.

The genetic evolutionary difference between distinct groups like Europeans, sub-Saharan Africans, and Australian Aborigines is something like 70,000 years of divergent evolution with very very minimal gene flow between the groups, in completely different environments. The genetic split between timber wolves and Chihuahuas was like 5,000 years ago and I bet they have common ancestors much more recently than that.

Re: Humans are more closely related than we commonly think

#20

Post by andi999 »

tasogare wrote: post #12
samatman wrote: post #6

So I was wondering if this article was just being incredibly misleading or straightforwardly lying, and I hit this: > “If you were alive at the genetic isopoint, then you are the ancestor of either everyone alive today or no one alive today,” Yeah. That's a lie. There's no way around it, this is a dishonest statement. I'm in no kind of mood to explain why that is, for pretty predictable reasons this conversation goes…

Well the most common ancestor is used to push a certain narrative about all people "being the same", while conveniently putting aside hundreds of thousands years of evolution, which are precisely the source of the present day differences, but that doesn’t mean it’s false either, as there is indeed a common ancestor if we look back far enough.

I believe for all people to be the same, ability of interbreeding should be considered enough. I agree pushing agenda on half truth is harmful.
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