Humans are more closely related than we commonly think
scientificamerican.com
scientificamerican.com
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 very different genotypes and phenotypes.
This is illustrated in the 2003 simulation as follows: Considering the ancestral populations alive at 5000 BC, close to the ACA point, a modern day Japanese person will get 88.4% of his ancestry from Japan, and most of the remainder from China or Korea, with only 0.00049% traced to Norway; conversely, a modern-day Norwegian will get over 92% of his ancestry from Norway (or over 96% from Scandinavia) and only 0.00044% from Japan. Thus, even though the Norwegian and Japanese person share the same set of ancestors, these ancestors appear in their family tree in dramatically different proportions.
A Japanese person in 5000 BC with present-day descendants will likely appear trillions of times in a modern day Japanese person's family tree, but might appear only one time in a Norwegian person's family tree. A 5000 BC Norwegian person will similarly appear far more times in a typical Norwegian person's family tree than he will appear in a Japanese person's family tree.
It helps to visualize this more as a mesh than a tree, or as a flowing river. The river divides around rocks and obstructions (those are points of temporary divergent evolution) but ultimately all flows together (convergent ancestry). We are truly one body of genetic material, and yet each is a unique combination of backwards traces.
It's really very cool IMHO.
And then what would an analogy look for prokaryotes - bacteria, archaea? If my understanding of biology is correct, it would be like an infinitely tall, densely tiered waterfall. There's some forward generational movement, but there's also plenty of lateral ones - exchanging gene packets "at runtime".
So like Adam and Eve? :-)
I guess it's kind of like the difference between a permutation and a combination.
In particular, if you have a male ancestor at the Identical Ancestor Point but the lineage from them to you passes through a woman at any point in the family tree, you would not get that male ancestor's Y-chromosome via that line of descent.
Or put yet another way, if you are male, you have 2^N (possibly overlapping) ancestors N generations back, but only _1_ ancestor N generations back that contributed your Y-chromosome. Comparing to a different male, the chance that you share Y-chromosomes is naively something like 1/P where P is the size of the male population at the time, while the chance that you share your ancestor sets is a much more complicated calculation, and the article claims it's ~1.
In the first the path goes through both fathers and mothers. This is easier to achieve, and so you get to it more recently. The second is harder and so happened longer ago.
There was too much time between them.
We focus too much on these two inputs, and forget the other (20) pairs of our nuclei.
Or: it's a DAG, not a tree.
If you look at one generation ago one have 2 * 2 ^ 0 ancestors, at two generations, one have 2 * 2 ^ 1 ancestors, etc. At 27 generations one apparently has more ancestors than people in the world at that time. This apparent paradox stems from the fact that we are heavily inbred.
Thus the article is correct.
I'm not following your point - maybe it's just a linguistic thing. To me, inbreeding implies relation, at least blood-relation, even when there was no other relation, e.g. conquering armies raping and pillaging.
No argument with your math.
"Monte Carlo simulations suggest the MRCA was born surprisingly recently, perhaps even within the last 5,000 years, even for people born on different continents."
Perhaps you're off by a 0 or two...?
The Americas may have been clearly separated for a while, but they have done so much interbreeding with people from other continents since 1492, that the common ancestor is more recent than that.
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.
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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.
Any citation?
https://en.wikipedia.org/wiki/Early_human_migrations#Homo_sa...
Europeans have pretty low levels of sub-saharan genetic markers, with some remnant markets in southern Europe dating to the late Roman era, diminishing substantially as you move north.
Given how humanity has evolved, "european" markers are a subset of the diversity found in subsaharan populations that are overrepresented from founder effects, with very few exceptions. 40,000 years ago sounds like a long time, but it really isn't.
You need an amazingly small amount of migration (about one person per generation) to keep a population in sync with each other genetically.
>You need an amazingly small amount of migration (about one person per generation) to keep a population in sync with each other genetically.
Well it depends on the size of the population, but even then I don't see how this can be the case. One individual only contributes half their genes to each child, so assuming 2 surviving children that's a 25% lost immediately in the next generation. In just a few generations about half the incomer's genes will be lost in this way. The remainder will likely persist, but equally the number of their descendants that have none or very few of their genes will rise to predominate. In a stable population of 1,000 people, one single individual is unlikely to contribute much more than 1/2,000th of the genes in circulation.
> When DNA recombines at conception, it only snips and stitches in a fairly limited number of places. It doesn't 'mix' finely like paint.
I had always assumed that clearly recognizable traits that children inherit from parents are simply based on the large influence of certain small pieces of DNA. Do you know a good text that discusses that?
I never understood this position from the logical point of view.
Say that you were put in front of two pictures that are entirely covered except for a small visible part each. The two visible parts of the pictures are different. Would you ever assume the parts that you can't see to be identical, or would you assume they differ from each other as much as the visible parts do?
Some very small genes have very large visible expression. Some large chunks of DNA have very little.
Let me change your italics:
Some very small genes have very large visible expression
So small parts of the DNA code for changes that we can visually appreciate. This doesn't mean that the rest of the DNA contains no variations, but just that we cannot see them. But it would be wrong to assume that the only parts that are actually different are those which encode for visible characteristics.
This seems like a clearly recognizable inherited trait, based on a large influence of certain small pieces of DNA. The abstract mentions eye color as well.
Well, for a start, this is completely wrong. Dogs diverged from wolves 20-40,000 years ago (lots of ambiguity over where exactly the divergence should be called), but from a now-extinct wolf species. While dogs and wolves _can_ interbreed, it doesn't happen naturally all that often (and when it does, it's pretty much all unidirectional; dog to wolf). Humans don't have the same issue.
A chihuahua, of course, is a result of deliberate and extreme forced breeding of a sort that (thankfully) has not really been practiced on humans. The closest parallel might be certain European royal families who had severe genetic diseases and abnormal physiology due to repeated inbreeding, but those were much, much less extreme. Dogs, though, were subject to fairly dramatic artificial selection from the start.
It also means that a modern Japanese person has thousands of "Japanese" ancestors from whom they received zero genes. Of course, this is a bit of misdirection, as the genes that one receives are not unique, but drawn from a pool of possible genotypes common to humanity. The matter of how closely we resemble each other is not one purely of ancestry, but of the size of that pool - our overall genetic similarity. From what I gather, it's not an exceptionally large pool. I may not have gotten whatever gene controls the formation of the human prefrontal cortex from the same nth ancestor as you, but I got it all the same.
Also, where does dominance play into this, I wonder?
This really seems to have some huge assumptions in there. What is commonly understood? I don't think there is much common understanding associated with this. Except maybe that we should treat individuals as individuals, rather than make strong distinctions based on group membership, regardless of any underlying distinctions in the groups. At least that's the noble intent -- I don't think any lies are layered on this.
Definition: An "infinitary species" is a set X of organisms which is (i) infinite, (ii) ancestrally closed (contains every ancestor of every member of itself), and (iii) as small as possible with those two properties (i.e., no strict subset of X has properties i and ii).
Theorem: In any infinitary species, every member is an ancestor of almost every other member (more precisely: of all but finitely many other members).
Proof: Let m be a member of an infinitary species X. Let S be the set of members of X who are NOT m or descendants of m. Let S' be S plus all ancestors of members of S. Since X is ancestrally closed, S' is a subset of X. S' is ancestrally closed by construction. S' does not contain m, so S' is a strict subset of X. Therefore, since X is as small as possible with properties (i) and (ii), it follows that S' must be finite (otherwise S' would be a strict subset of X with properties i and ii). Thus S is finite, proving the theorem, QED.
Here is the paper, it has many other fun results like that: https://arxiv.org/pdf/1201.2869.pdf
> No large group is known to have maintained complete reproductive isolation for extended periods.
The paper's conclusion:
> Given the remaining uncertainties about migration rates and real-world mating patterns, the date of the MRCA for everyone living today cannot be identified with great precision. Nevertheless, our results suggest that the most recent common ancestor for the world’s current population lived in the relatively recent past—perhaps within the last few thousand years. And a few thousand years before that, although we have received genetic material in markedly different proportions from the people alive at the time, the ancestors of everyone on the Earth today were exactly the same.
> Further work is needed to determine the effect of this common ancestry on patterns of genetic variation in structured populations. But to the extent that ancestry is considered in genealogical rather than genetic terms, our findings suggest a remarkable proposition: no matter the languages we speak or the colour of our skin, we share ancestors who planted rice on the banks of the Yangtze, who first domesticated horses on the steppes of the Ukraine, who hunted giant sloths in the forests of North and South America, and who laboured to build the Great Pyramid of Khufu.
Also also genes that don't confer any particular advantage tend to peter out when inserted into large populations.
Above my pay grade but I think that argues that the genetic difference that do exist tend to either not confer any particular advantage, like maybe shape of your nose, hair color. Or confer some limited advantage, skin pigmentation for instance seems to be strongly associated with solar radiation and dietary availability of Folic Acid and Vit D.
Nose shapes are selected for by temperature and humidity. That's probably not the only selection pressure, but it's a major one.
Not sure that's true.
Natural selection is not the only force driving evolution.
Neutral and nearly neutral (slightly deleterious) alleles can be fixed in a population by random genetic drift.
Source: https://sandwalk.blogspot.com/2020/10/on-importance-of-rando...
As a mathematical model, I don't doubt the assertion that it's possible one bit. But humans don't interbreed like that.
IMO all this tree stuff doesn't pass my "finitist efficiency test". I don't think we should choose to work with this these super large exponential numbers just to quotient them out. Better to just us the "Family DAG" from the get-go.
What must be done by real demographers, but never covered in these articles from the general public, is some sort of "outbread---diversity" distribution. There is a clearly a conservation law in that genetic variation at larger scales depends on inbreeding / genetic homogeneity at smaller scales.
While I doubt the phenomenon is scale-free, there is still variation in the possible distributions at every scale. I want to know where humans have lied in that distribution-of-distributions over time. E.g. Europe is very homogeneous but if there was something more egalitarian than federalism would it be even more homogeneous?
My hunch is "no" because most of these Eurasian hierarchical societies had tones of elite man + non-elite women illegitimate children who were denied elite privileges, but I'd still like to see the definitive answer.
This Is Why Inbreeding Is So Dangerous https://www.youtube.com/watch?v=hmv-z851BOE
I'm pretty this is why people all over the world like to keep track of their ancestry. People who don't will be more closely inbred.
Not sure about that. Tracking ancestry probably became a middle-class hobby in mimicry of the aristocracy in the 19th and 20th centuries, and the aristocracy in most places were notoriously pretty much okay with marrying cousins.
All the article seems to be based on the Out of Africa hypotesis, but what about the multiregional hypotesis?
The strong multi-regional hypothesis is essentially a dead issue; didn't survive contact with modern genetics. There's now some evidence for regional admixture for genetics from archaic humans with Homo sapiens, and this is sometimes called (kind of misleadingly, IMO), the weak multi-regional hypothesis.
Haven't recent discoveries undermined this theory?
Side track: there's a serious argument that parts of Bible are translated pretty badly (which puts into perspective people quoting it verbatum). I've been told of a specific example where (excuse the paraphrasing) Eve is said to emerge from the side of Adam, as in from the interior of his torso, and it's popularly taken to be a metaphor. Some interpret it to mean that a woman is somehow a byproduct of man, and thus lesser. Anyway, someone actually took up checking the translation and concluded that it's not that Eve emerged from Adam's side, but that she emerged at his side, as in stood by him. Going by what's written in a super old book that's been translated and altered many many times is, well, adventurous.
This translation https://www.biblegateway.com/passage/?search=Genesis%201&ver... looks much better
"So God created mankind in his own image, in the image of God he created them; male and female he created them"
and it makes much more sense in context of the rest of the Bible, especially New Testament.
https://www.biblegateway.com/passage/?search=Genesis+2%3A21&...
> So the Lord God caused the man to fall into a deep sleep; and while he was sleeping, he took one of the man’s ribs and then closed up the place with flesh.
If the number of ribs is the same, then it's either that God didn't create a woman from man's rib, or he took two ribs, one from each side, and created two women.
> The baculum (also penis bone, penile bone, or os penis, os genitale or os priapi) is a bone found in the penis of many placental mammals. It is absent in the human penis, but present in the penises of other primates, such as the gorilla and chimpanzee.
Edit: seems that there is some theory advanced by real biblical scholars, but it also seems that it is highly unlikely to be true:
https://www.haaretz.com/jewish/god-didn-t-use-adam-s-penis-b...
Which is of course a good reason not to take the Bible at face value as historical overall (even if some of the parts are reasonably historical).
https://www.theonion.com/sumerians-look-on-in-confusion-as-g...
(1) In Genesis 1 the god creates animals before the man. He creates man and woman and tells them to be fruitful and multiply.
(2) In Genesis 2 God creates Adam before animals. Adam and Eve are put into special place called Eden and are not aware of their sexuality until they sin.
Judaism is folk religion of the Israelites, not universal religion. Old testament tells the story from the point of Jewish tribes. in it's current form it was created around (538–332 BC). Israelites “God’s chosen people” in the old testament. All the interaction with the god and men is actually about Israelites and God, not the humanity and God.
One way to think this is that genesis 2 is the general creation myth, Genesis 2 is the story of how God created two first Jews. Jewish people started to separate religiously from other Canaanites between 1200 and 1000 BCE, so maybe you can put the Adam and Eve myth there.
> Judaism is folk religion of the Israelites, ...
In the Hebrew Bible, the tribe of Judah was just one of twelve tribes. Nowadays, the Samaritans still consider themselves distinct from the Jews with different tribal lineage.
No. Genesis is not a historical document. It is an allegory about creation. Adam and Eve need not necessarily be the first humans, but they were the first to receive a divine spark called "the soul".