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>Even a single fertile couple cannot successfully reproduce in the wild (if you doubt this, watch a few episodes of Naked and Afraid). The minimum viable reproductive unit for homo sapiens is a tribe or a village.

Do you have evidence for this that's not a reality TV show?

Edit: I have found the Lykov family who had two children in isolation; they did already have two children who would have been 13 and 6 at the time of the third child's birth in isolation. https://en.wikipedia.org/wiki/Lykov_family

I too would like to see a citation for this at least. It doesn't make sense to me why this would be the case.

Me too. Although I thought what he was going to say is the limited genepool would make grandchildren impossible (well nearly...) and generations after that impossible.

https://news.ycombinator.com/item?id=17127687

People are asking for citations to actual literature that support your claim that a pair of fertile people can't reproduce. I think what you're actually saying is that you can't bootstrap a viable population from a pair of people (which is definitely true from a population bottleneck point of view), but I think you're massively overstating your case. It would really help if you could point to some modern well-accepted textbook or paper that supports your claim.

That's the concept of minimal viable population (https://en.wikipedia.org/wiki/Minimum_viable_population). Basically it means how much inbreeding is acceptable to have viable descendants.

I'm aware of this concept but the comparison to Naked and Afraid and literally sterile ants made me think he was referring to some distinct idea.

I understand. In fact, classifying individual social insects as organs doesn't sit well with me also, it feels more like philosophy than biology. I think it also ignores other possibilities that could explain why sexual reproduction is reserved to a subset of a population, but well, I don't teach evolution.

I don't know what evidence you'd want. The claim seems self-evidently true to me.

You were able to find one wiki article on a curious case of a family who, unlike billions of other people, survived as individuals for less than 50 years in partial isolation. That's impressive, but it doesn't change the basic facts of human survival.

Case in point, in the first paragraph of the link you provided about the Lykovs, the article says only one daughter yet survives (as of 1988, so they are probably all gone now).

Minimum viable populations are partially about day to day survival and team work, but in the long term it's about genetic diversity which is critical for long-term population survival. Evidence: all of biology?

Abakan Range is rather difficult place to live which is why they where left alone and the family was not from a culture of nomads. Yet, Agafia made it to 70 and is still alive.

That suggests it's far more viable than you might think. It's just more attractive places to live currently have people living there. Opportunity's for solitude where far greater when global population was lower, but it's unlikely for such things to enter written history.

> Agafia made it to 70 and is still alive

But left no descendants.

> Do you have evidence for this that's not a reality TV show?

Yes. Let's start with the fact that there are no recorded instances of an isolated human couple successfully reproducing in the wild ever. Merely having a baby doesn't count. To be a viable evolutionary strategy you have to raise that baby to maturity and then that baby has to reproduce themselves.

In fact, this is not unique to humans. It's true of all simians. In fact, it's true for the vast majority of mammals. The only exceptions I can think of are some species of cats: leopards, cheetahs, tigers, mountain lions.

We can also reason from first principles: you need a minimum viable population in order to maintain genetic diversity. So even if it were possible for isolated human couples to reproduce, you'd need more than one instance of this, and these families would somehow have to find each other in order to procure mates. How are they going to do that?

Don't mistake modern density for a requirement. It's hard to find instances of anyone living alone for long periods, but that likely changes as you go back and there where fewer people and those people where more able to survive in the wild.

I remember going into back country with some friends as a teen, miles into 'the middle of nowhere'. Second day camping I see someone run by in yoga pants pushing a stroller as it turns out we where about 300 feet from a ski trail and people would run down the mountain in the summer for fun.

Don't mistake a small loose end in a complex argument condensed to fit in an HN comment for proof that the argument is wrong.

Well the holes in your arguments are deeper than that. A viable strategy need not be the only or even the optimal strategy.

If couple has kids and those kids find someone in a local tribe then both tribes and lone families would have worked. In effect you are trying to redefine his argument not just in terms of recorded history but also both couples not an individual one.

> If couple has kids and those kids find someone in a local tribe then both tribes and lone families would have worked.

You're attacking a straw man. Of course a couple can reproduce if they are in proximity to a tribe. But that still requires a tribe. It is a couple in isolation that is not viable.

The couple are irrelevant at that point. People can travel ~10,000 miles a year on foot. The fact their kids leave in no way impacts them being in isolation. Heck, someone can know where other people are and still be isolated.

QED they can reproduce in isolation.

I rarely see people on HN miss the point quite this badly. Reddit, yes, but not here.

The point is: for your scenario to play out, a tribe has to exist (and it has to be close enough for the couple's offspring to find it, but that's a detail). No tribe, no viable reproduction. Hence, the tribe is the minimum viable unit, even if it also occasionally supports an isolated couple somewhere in the vicinity.

Your argument is only true in the trivial sense that sexually reproducing organisms are only viable in larger numbers than a single pair; but that's a distinction that doesn't demarcate anything interesting. Humans are like ants, you say, but your argument also leads to the same conclusion about tigers, bears and other solitary animals in that they need more than a breeding pair to be viable. It descends into tautology.

Yes, humans are somewhat like ants in that they are usually social. Humans are adaptable enough to survive in pairs, though lack of specialization means they won't necessarily live the most comfortable life, so it would be an unusual choice. But there's nothing elective about ants' socialism. So in the end I don't think your argument works.

> your argument also leads to the same conclusion about tigers, bears and other solitary animals in that they need more than a breeding pair to be viable

No. Those species have specialized adaptations that allow them to live in isolation, which humans lack. And it's not just humans. All simians lack these adaptations. Indeed, the vast majority (perhaps all -- I can't think of a single counterexample) of non-carnivore mammals lack them.

Isolation does not mean other groups don't exist. It means lack of contact, and the adults don't need contact and as I have said children can move as happens with many territorial animals.

Comparing minimum viable populations to sterile ants seems to confuse the issue. Applying concept of eusociality in ants to humans seems to be somewhat of a fringe idea https://www.prospectmagazine.co.uk/magazine/edward-wilson-so...

Ever heard of bears? I don't believe any of them have something that could be called a tribe (unless you redefine any form of family to be one). They simply don't have a source of food that could sustain any nontrivial population in small territory. Even living alone most of there lives wouldn't stop them from finding a mate and having an offspring.

No, I have never heard of bears. What is a bear? And what do bears have to do with humans?

For Lisper's overall claim to be valid, you only need the weaker result that an isolated couple's expected number of children living to adulthood is less than 2.

evidence you need to start with more than a single breeding pair to not go extinct

https://www.researchgate.net/publication/224771432_Lynch_M_C...

The OP isn't making absolute points, this is the point. An ant isn't really an organ, at least using normal word meanings. He means that it is effectively an organ, from a reproductive perspective.

People obviously are viable reproductive organisms in a technical/literal sense. But... the way people (and our nearest cousins) actually reproduce is in couples within a tribe/village/troop. People are evolved to reproduce this way and people evolved by reproducing this way.

Computational biologists, specifically those who utilize network models, are hoping to make this idea more concrete. It's well-known now that some real-world (including biological) networks are scale-free (mathematically, their degree distribution follows a power law). As an example, many gene networks have "hub" genes, that are related to several genes, whereas the median connectivity of a gene is fairly low.

Separately but also related, there's a growing sentiment that biological networks are self-similar - higher-level network-modeled abstractions are in fact topologically similar to lower-level subnetworks. This analogy may seem almost Hofstadter-esque at this point, but in a few years, who knows...

Some links:

[1] https://www.nature.com/articles/srep07628

[2] http://rsif.royalsocietypublishing.org/content/9/74/2131

One of my favorite creatures in all the world is the lowly Trichoplax:

> Trichoplax adhaerens is the only extant representative of phylum Placozoa, which is a basal group of multicellular animals (metazoa). Trichoplax are very flat organisms around a millimetre in diameter, lacking any organs or internal structures. They have two cellular layers: the top epitheloid layer is made of ciliated "cover cells" flattened toward the outside of the organism, and the bottom layer is made up of cylinder cells that possess cilia used in locomotion, and gland cells that lack cilia. Between these layers is the fibre syncytium, a liquid-filled cavity strutted open by star-like fibres.

https://en.wikipedia.org/wiki/Trichoplax

I like these creatures because they are on the cusp of multicellularity: you can force them through a sieve that separates their cells which will then crawl around independently and try to reform the organism. You can dye two trichoplax different colors, force them through the sieve, and the cells will mix and form piebald organisms. So, they're like tribes of cells (IMHO.)

Fascinating observations about Cells and DNA !!!!

> This sort of organizational grouping is found at all of the levels of abstraction in life. Even your DNA is not really a unified whole, it's a bunch of genes that have glommed together in a cooperative effort to reproduce themselves, but it's not an organized or homogeneous effort. That's why you have freeloaders (which are called "junk DNA") and defectors (cancer) who put their own interests above those of the group. What happens at the cellular and molecular level is really not so different from what happens in human societies. The presence of brains changes the dynamic, but not in any fundamental way. At the end of the day, it's all just self-replicating information looking for an ecological niche and a reproductive edge. The idea that human individuals are somehow special in this process is mostly a prejudice brought on by our particular point of view, namely, the fact that our thoughts reside in brains that are strongly bound to bodies. The ability to see beyond onesself can be both powerful and humbling.

Ant Colony Is Likened to Human Body : a 1985 Research study https://www.washingtonpost.com/archive/politics/1985/07/05/a...

Secrets of a Superorganism https://askabiologist.asu.edu/explore/secrets-superorganism

Your exposition of Dawkins' ideas is neat, and probably helpful to people in an introductory biology course. I'd like to help clarify some of your comments on the genome.

> Even your DNA is not really a unified whole, it's a bunch of genes that have glommed together in a cooperative effort to reproduce themselves, but it's not an organized or homogeneous effort. That's why you have freeloaders ("junk DNA") and defectors (cancer genes) who put their own interests above those of the group.

"Cancer genes" don't exist in the sense that there aren't genes that specifically cause cancer. If there were then every individual with a full gene complement would get cancer. What you're referring to are certain alleles that can arise which change cellular processes so as to break cooperative patterning of cell behavior. If you're lecturing in evolution it might be nice to use a technically correct description to match the Dawkinsian semantic splicing you're resting on :) Call them "oncogenic alleles" instead.

"Junk DNA" is a blind concept that conflates sequence complexity with function. The argument goes that these pieces of DNA are just copies of each other and serve no obvious purpose, thus they are junk that "freeloads" off their host. This ignores the fact that these elements exist in virtually all complex organisms, and have lineages that last tens or hundreds of millions of years, which is longer than the lifespan of most species. If they were only an energetic drag on their host they would be selected out over these time scales. Instead, they appear to serve important purposes in genomes. There is a huge amount of evidence that this "junk" is also an "organ" of the genome that provides essential function in an evolutionary sense. This perspective is old, more than 30 years, and the first reference to it I'm aware of is from a study in 1983 that showed that Escherichia coli with transposons evolved faster than those without: https://www.nature.com/articles/303633a0

Agreed on all counts. (Condensing a complex argument down to an HN comment requires some rhetorical compromises.)

This seems very similar to the ideas expressed in "The Selfish Gene" by Richard Dawkins.

https://en.wikipedia.org/wiki/The_Selfish_Gene

Yes, that is exactly where this example comes from. I've added a credit.

What happens at the cellular and molecular level is really not so different from what happens in human societies.

I am not quite sure to what extent you mean this. I would add that the bottle neck on evolutionary futures for our genes imposed by our reproductive system is very strong, and that there is no obvious analogy in societies. The existence of such a strong bottleneck of course shifts the game theoretical dynamics of cooperation and defection, strongly enabling cooperation between somatic cells (as you say, with cancer as an exception).

Interesting question: indeed why would evolution select for genes that produce sterile individuals (for ants)? What is the selection pressure ensuring only the queen reproduces?

Firstly, the drones creating offspring would lead firstly into a population explosion followed by a population collapse after viable and attainable nutrition sources nearby have been depleted. Once the population collapses to low enough numbers, even cannibalism does not work anymore and eventually that genetic line dies out.

Also, it is presumable there would be fighting over resources, and maybe multiple genetic makeups within a single nest also opens up the door for attacks from other nests, since detecting who is a friend and who is not could be difficult, making the nest (and its genetic makeup) vulnerable.

Also, the minimum reproductive unit for a mobile homo sapiens is obviously a man and a woman. But is it viable, too? I say yes. Their offspring can wander out away from their parents and find another isolated offspring that is fsr enough genetically, and create progeny and repeat the process. If the humans are somehow not mobile, then a larger group ("tribe") is needed to avoid inbreeding with its detrimental effects.

> But is it viable, too? I say yes.

But all the evidence says no.

This is not a puzzle, and your answer is not a solution. It's formally wrong in terms of actual biology. Another way to think of it is as a narrative that attempts to explain- but it isn't a particularly useful one. It's not a "right/wrong" (and it's not something people can "figure out").

That some members of a population are sterile doesn't require you to completely rearrange your definition of biology, speceis, and organism.

> That some members of a population are sterile doesn't require you to completely rearrange your definition of biology, speceis, and organism.

It is not "some" ants that are sterile. The vast majority of them (like >99%) are sterile. That does demand an explanation.

> The answer is that ants are not organisms, they are organs. The ant colony is the organism.

I am confused by this, because this seems to be the "group selection" idea that is vociferously rebutted by Dawkins and others.

It is really not clear to me what the bright line is between group selection and kin selection. If social groups are genetically similar (which is most often the case in nature and human society), group selection and kin selection appear to be equivalent.

To really answer this you should read "The Selfish Gene." But the TL;DR is that the unit of selection in Darwinian evolution is neither the organism nor the group, but the gene. Ant colonies are the phenotype of a group of genes that glommed together over the years to form an evolutionarily viable unit. But the unit is not what is being selected ever, it's the individual genes. The phenotype of a gene is not necessarily constrained by any physical boundaries. (For example, the phenotype of the human genome extends into outer space!)

> To really answer this you should read "The Selfish Gene."

I did. Well the first several chapters at least. I did not find a convincing answer to the question I am raising here.

> The phenotype of a gene is not necessarily constrained by any physical boundaries.

Sure it's not necessarily constrained. But in practice there is very high correlation between family relatedness and physical proximity / social group.

If the main rebuttal against group selection is "families can be spread out", I don't think that warrants the level of criticism that is leveled at it. An organism surrounded by genetically unrelated peers is the exception, not the rule.

EDIT: Reading a bit more, I think I may be understanding this distinction better. "Kin selection" and "group selection" are more different than the names suggest. "Kin selection" means that natural selection incentivizes an individual to be altrustic towards their own kin. "Group selection" means that natural selection will favor the survival of an entire group over another group based on the comparative genetic strengths of the two groups.

Yes, your edit got it exactly right.

I hope you give the mechanism in the lecture.

You are not wrong, but the way you answer it it is just concept definition.

Yes, of course. It's usually an hour-long lecture. There's a lot more content than will fit in an HN comment.

I found this very enlightening, thank you.

You bet. Glad it was useful.

This was fascinating.

Can you recommend any good books about genetics and natural selection to people who don't have a biology background? I can handle some math, but I just break software for a living and I don't know biology.

Sorry for the sidetrack, but thanks for posting this. I've always wondered about some of the higher order implications of natural selection, and ants are a great example. Like how megacolonies take in ants from other places, that's so crazy because it doesn't make sense once you're looking at a small enough perspective but makes perfect sense at a larger scale. Bees are cool too.

The classic work on this topic is "The Selfish Gene" by Richard Dawkins, and its more technical sibling, "The Extended Phenotype."

Also interesting is Why Evolution is True by Jerry Coyne

Ah! I had heard of that before but I didn't remember.

Thanks!

Huh, this makes me think, culture is like artificial selection. Some “organisms” have evolved to live off of the land, and others evolved to live off of other humans!

Exactly right. This is in fact what the word "meme" was originally coined to describe.

Yes, obviously. But I am honestly baffled here. I mean, when did anyone really seriously argue otherwise? Isn't that already universal knowledge what you are describing here?

(Well, depends a bit on the definitions, I'd still say that ants are organisms, but so is the ant colony, and yes, you always have to see the bigger picture)

I don't get what the NYT is trying to achieve with their "reporting" here.

(BTW, the title here on HN has been changed, for anyone coming a bit later to these comment threads)

> Isn't that already universal knowledge what you are describing here?

Not only is it not universal knowledge, there are substantial cohorts of people who will vehemently deny that it is true. In fact, there are people asking for additional evidence in other branches of this very discussion!

Not sure, but I don't think any would qualify as fundamental denial. Just questions about some specifics, details, and their evidence etc..

I mean, nothing that would be relevant to the question at hand, in my opinion.

Because the topic still is as linked above, and subsumed in this simple proposition: The genome varies from cell to cell.

Great. What a discovery! More news at 11!

Or is someone seriously arguing that genetic mutation is not universal knowledge?

(Excluding "flat-earth" level stuff, but I would assume that as given on HN. Maybe I am wrong again)

> Or is someone seriously arguing that genetic mutation is not universal knowledge?

Well, no. But there are a lot of people who vehemently deny that humans are in any way analogous to ants.