Will we become an 'artificial' species?

[colin]

On the recommendation of another 'Fool' interested in science on these boards I am reading Adam Rutherford's book 'A brief history of everyone who ever lived', while some of the detailed stuff leaves me a bit glassy eyed what has become most memorable is the insight into our common ancestry. For instance everyone of European descent shares a common ancestor at a point in our family trees about 600 years ago, go back a thousand years and 80 % of all people living in Europe at that time are the ancestors of all Europeans today, trace our individual family trees back 3,400 years and everyone in the world today shares a common ancestor with everyone else in the world.
On Radio 4s Inside Science programe today the recent gene editing of twin girls by a 'rogue' Chinese scientist to convey HIV resistance to the descendants of a man infected with HIV was discussed. It seems to me that at sometime in the future much sooner than 3,400 years given how much we travel, then everyone in the world will share one or both of these twins as an ancestor, will that make us an 'artificial' species not wholly created by nature?

[swill453]

trace our individual family trees back 3,400 years and everyone in the world today shares a common ancestor with everyone else in the world.
...
It seems to me that at sometime in the future much sooner than 3,400 years given how much we travel, then everyone in the world will share one or both of these twins as an ancestor, will that make us an 'artificial' species not wholly created by nature?

I think your mathematics is flawed.

Simplistically, 1 person 3400 years ago has as descendants 6 billion today.
So 1 person today will have 6 billion descendants in another 3400 years.
But by that time the population of the earth will be a lot more than 6 billion (barring disasters or other curtailments, which will equally affect the "artificial" bloodline).

Scott.

[EssDeeAitch]

trace our individual family trees back 3,400 years and everyone in the world today shares a common ancestor with everyone else in the world.
...
It seems to me that at sometime in the future much sooner than 3,400 years given how much we travel, then everyone in the world will share one or both of these twins as an ancestor, will that make us an 'artificial' species not wholly created by nature?

I think your mathematics is flawed.

Simplistically, 1 person 3400 years ago has as descendants 6 billion today.
So 1 person today will have 6 billion descendants in another 3400 years.
But by that time the population of the earth will be a lot more than 6 billion (barring disasters or other curtailments, which will equally affect the "artificial" bloodline).

Scott.

Interesting point you make there on population growth. Hans Rosling in his excellent book "Factfulness" extrapolates from empirical evidence that as communities/countries get richer, population growth slows and ultimately reverses. However, data suggests that world population will increase to around 11 billion by the end this century and then plateau.

It's going to be damned crowded that's for sure.

Watch this short video (1m 30 sec) of Hans Rosling explaining https://www.gapminder.org/answers/how-d ... on-change/

[ReformedCharacter]

Depends how you define 'artificial' but in some respects humans became 'artificial' when self-consciousness evolved because everything developed, by degree, from that.

RC

[colin]

trace our individual family trees back 3,400 years and everyone in the world today shares a common ancestor with everyone else in the world.
...
It seems to me that at sometime in the future much sooner than 3,400 years given how much we travel, then everyone in the world will share one or both of these twins as an ancestor, will that make us an 'artificial' species not wholly created by nature?

I think your mathematics is flawed.

Simplistically, 1 person 3400 years ago has as descendants 6 billion today.
So 1 person today will have 6 billion descendants in another 3400 years.
But by that time the population of the earth will be a lot more than 6 billion (barring disasters or other curtailments, which will equally affect the "artificial" bloodline).

Scott.

Yes after making the post I realized that the sharing of common ancestors is a mathematical requirement of population growth but it is extremely unlikely that population growth in the future will be anything like past growth, indeed in a thousand years times world population may well be smaller than it is today in which case these Chinese twins may well leave no descendants and if they do it will take a longer time for their genes to spread throughout the gene pool than it would have done under historical scenarios of population growth.

Simplistically, 1 person 3400 years ago has as descendants 6 billion today.
So 1 person today will have 6 billion descendants in another 3400 years.

Not quite, everyone alive 3,400 years ago is the ancestor of everyone alive today due to the convoluted nature of intertwining family trees. That's what I took from A.Rutherfords book.

[mc2fool]

...trace our individual family trees back 3,400 years and everyone in the world today shares a common ancestor with everyone else in the world.

...everyone alive 3,400 years ago is the ancestor of everyone alive today due to the convoluted nature of intertwining family trees.

Those are two totally different statements, and while the first is possible the second really can't be, as it would only need one person alive 3,400 years ago to have died childless to falsify it.

[ursaminortaur]

...trace our individual family trees back 3,400 years and everyone in the world today shares a common ancestor with everyone else in the world.

...everyone alive 3,400 years ago is the ancestor of everyone alive today due to the convoluted nature of intertwining family trees.

Those are two totally different statements, and while the first is possible the second really can't be, as it would only need one person alive 3,400 years ago to have died childless to falsify it.

Yes the second statement should be more like

everyone alive 3,400 years ago who has still living descendents is the ancestor of everyone alive today due to the convoluted nature of intertwining family trees

There will have been many people living 3,400 years ago whose descendents have died out before the current living generation but if a person living 3,400 years ago has any descendents still living today then they should statistically be an ancestor of everyone living today.

Although it is getting closer to being true I doubt it is actually true at the moment. There are still isolated tribes around the world in which some tribal members won't share a common ancestor with a european unless you go back far beyond 3,400 years ago.

As to the future. Yes, if we introduce changes into human genomes then assuming those individuals have descendents and the changes are evolutionarily advantageous then they will spread. In that respect such changes would be no different to natural mutations such as the ability of human adults to consume milk spreading after humans domesticated animals.

Of course in the longer term we may become a truly artificial species by either merging with our mechanical creations or uploading our consciousness into machines.

[colin]

Yes, the book points that a mathematician calculated that of all Europeans alive 1000 years ago 80% of them must be the ancestors of every person of European descent alive today, the other 20% left no descendants who are alive today, DNA testing has confirmed the theoretical result. 1000 years is rather further back than the 600 years to where Europeans share a common ancestor, later in the book it states that everyone in the world shares a common ancestor at some point along a line of descent going back 3,400 years so we must all be descended from ancestors who consisted of the entire population of the world at some date before that, but it does not say when.

In that respect such changes would be no different to natural mutations such as the ability of human adults to consume milk spreading after humans domesticated animals.

In a very fundamental respect artificially changing our genes is completely different because it will not be the result of a random mutation, perhaps natural selection will weed out the artificially induced mutation if it has unforeseen negative consequences, but it seems to me that a huge milestone has been passed with profound consequences to our species. In the radio 4 Inside Science program today it was suggested that this may not have been the first instance of such gene editing just the first public announcement of it by a naive scientist who never thought that he would be thrown in jail. This CRISPR gene editing tool seems to be so easy to use that it's inevitable that this will be used again to make heritable changes to the dna of a human egg or embryo but perhaps without the publicity .

[mc2fool]

Yes the second statement should be more like

everyone alive 3,400 years ago who has still living descendents is the ancestor of everyone alive today due to the convoluted nature of intertwining family trees

There will have been many people living 3,400 years ago whose descendents have died out before the current living generation but if a person living 3,400 years ago has any descendents still living today then they should statistically be an ancestor of everyone living today.

Although it is getting closer to being true I doubt it is actually true at the moment. There are still isolated tribes around the world in which some tribal members won't share a common ancestor with a european unless you go back far beyond 3,400 years ago.

LOL, I like the way you correct it to something at least theoretically possible, and then go on to say you doubt it's true.

Actually, I think it's probably even less true than you imply, as it's not just isolated tribes but isolated continents. The Americas were populated around 20-15,000 years ago and then had very little outside genetic input until 500 years ago. Is that long enough for the descendants of the 50 million people that were there when Columbus turned up to have become universally crossed with the rest of the world populations, especially considering that it took quite a long while for sizable numbers to arrive, and the ongoing cultural separation? Hmmm.....

Similarly so for Australia, the aboriginals arrived as a single set of groups some 50,000 years ago and stayed in isolation until Europeans turned up a couple of hundred years ago, and still then stayed separate.

The perhaps more surprising ('twas to me at least) and less obvious case of genetic isolation is Africa. The Neanderthal genome project found that the Out-of-Africa migrations interbred with Neanderthals, and then kept going, the upshot of which is that everybody of the rest of the world populations today has 1-4% Neanderthal DNA (and a smattering of Denisovan) in them. However, not so for sub-Saharan African populations, in which Neanderthal DNA is generally absent.

The lack of Neanderthal DNA in sub-Saharan African populations today compared with the universality of it in everyone else indicates that sub-Saharan Africans have been largely genetically isolated for at least 40,000 years....(or maybe it's the rest of the world that's been isolated, take your choice )

[mc2fool]

...everyone in the world shares a common ancestor at some point along a line of descent going back 3,400 years so we must all be descended from ancestors who consisted of the entire population of the world at some date before that...

Yes, when the speciation event occurred that created the very first breeding humans and the entire human population of the world was two, Adam and Eve if you like.

Oh, ok, not just two but still a very very very few, right at the beginning of the species. After that it doesn't follow at all, as it's entirely possible, indeed, certain, that some, even large sections of the world's population, would have died out without leaving any descendants. Disease, natural disasters, etc.

But we don't even have to go that far. As I said above, it only take one childless person to disprove the statement.

[9873210]

Yes the second statement should be more like

everyone alive 3,400 years ago who has still living descendents is the ancestor of everyone alive today due to the convoluted nature of intertwining family trees

Although it is getting closer to being true I doubt it is actually true at the moment. There are still isolated tribes around the world in which some tribal members won't share a common ancestor with a european unless you go back far beyond 3,400 years ago.

LOL, I like the way you correct it to something at least theoretically possible, and then go on to say you doubt it's true.

Actually, I think it's probably even less true than you imply, as it's not just isolated tribes but isolated continents. The Americas were populated around 20-15,000 years ago and then had very little outside genetic input until 500 years ago. Is that long enough for the descendants of the 50 million people that were there when Columbus turned up to have become universally crossed with the rest of the world populations, especially considering that it took quite a long while for sizable numbers to arrive, and the ongoing cultural separation? Hmmm.....

...

The lack of Neanderthal DNA in sub-Saharan African populations today compared with the universality of it in everyone else indicates that sub-Saharan Africans have been largely genetically isolated for at least 40,000 years....(or maybe it's the rest of the world that's been isolated, take your choice )

It takes very little contact to intertwine the family tree between continents. Possibly as little as a single human. The exponential growth in the number of descendants per generation means that not only can a single traveller become, over time, the ancestor of the entire continental population but also that any particular marker (such as Neanderthal genes) would show up in very few of their descendants. A largely isolated population is not a totally isolated population.

We know that Vikings were in North America 1000 years ago and had contact with North Americans on both the mainland and Greenland. Over the last 2000 or more years there have been many seafaring cultures that have at least the potential for involuntary one-way intercontinental journeys in many directions.

[mc2fool]

It takes very little contact to intertwine the family tree between continents. Possibly as little as a single human. The exponential growth in the number of descendants per generation means that not only can a single traveller become, over time, the ancestor of the entire continental population but also that any particular marker (such as Neanderthal genes) would show up in very few of their descendants. A largely isolated population is not a totally isolated population.

We know that Vikings were in North America 1000 years ago and had contact with North Americans on both the mainland and Greenland. Over the last 2000 or more years there have been many seafaring cultures that have at least the potential for involuntary one-way intercontinental journeys in many directions.

Agreed to a lot of that, except that it isn't exponential, and the sparseness of population groups and the difficulty of travel until recently makes it entirely possible that Leif Erikson's genes have never crossed with any Patagonian's, and even if they had those lines could have died out or remained within relatively small groups. Numbers aren't the only limiting factor nor the guaranteeing one.

This all reminds me of an over dinner conversation at a Homo Erectus excavation I was on some decades ago, when the Prof. in charge of the dig declared that we were all descended from Caesar (the Prof. was Italian), and went on to use powers of 2 to prove it. 2000 years = at least 80 generations, 2^80 is by far more people than have even lived. therefore....

He saw the flaw in the purely mathematical approach when I pointed out that by that logic we were also all descendants of Jesus. (That was before Dan Brown's little ditty, although well after the less widely known The Holy Blood and the Holy Grail.)

To give him his due though, he was of the opinion that we'd interbred with Neanderthals, something for which there was (and still is, I believe) no archaeological evidence for (and may never be if the cross didn't include any cohabitation).

[XFool]

The perhaps more surprising ('twas to me at least) and less obvious case of genetic isolation is Africa. The Neanderthal genome project found that the Out-of-Africa migrations interbred with Neanderthals, and then kept going, the upshot of which is that everybody of the rest of the world populations today has 1-4% Neanderthal DNA (and a smattering of Denisovan) in them. However, not so for sub-Saharan African populations, in which Neanderthal DNA is generally absent.

I can't see why that should be "surprising", surely by present understanding it's pretty well required!

AFAIK, as a species "Neanderthals" evolved outside of Africa (although in turn their ancestors, like us, evolved in Africa) so it would only be subsequent 'Out of Africa' species that could have cross bred with them.

Interesting points:

What led some hominid species to leave sub-Saharan Africa? Was there even a Sahara as we know it at those times?

I also heard claims have been made for 'ghost' hominid species identified via the DNA of Africans. That is, species otherwise currently unknown via any identified palaeontological specimens.

And, bearing in mind the above, I still can't quite get my head around exactly what is meant by say "Neanderthal" (or any other) DNA in humans, how is 'non Homo Sapien DNA' identified as such?

[mc2fool]

The perhaps more surprising ('twas to me at least) and less obvious case of genetic isolation is Africa. The Neanderthal genome project found that the Out-of-Africa migrations interbred with Neanderthals, and then kept going, the upshot of which is that everybody of the rest of the world populations today has 1-4% Neanderthal DNA (and a smattering of Denisovan) in them. However, not so for sub-Saharan African populations, in which Neanderthal DNA is generally absent.

I can't see why that should be "surprising", surely by present understanding it's pretty well required!

AFAIK, as a species "Neanderthals" evolved outside of Africa (although in turn their ancestors, like us, evolved in Africa) so it would only be subsequent 'Out of Africa' species that could have cross bred with them.

Yes, but that's besides my point. My comment was about what happened after that.

The lack of Neanderthal DNA in sub-Saharan African groups indicates that the descendants of the Out-of-Africa groups didn't -- in the 40,000 years following the last possible interbreeding with Neanderthals -- spread back into sub-Saharan Africa and promulgate their acquired Neanderthal DNA there. Some, sure, but not in any significant numbers at least.

That I find a little surprising, seeing they managed to spread to pretty much every other corner of the planet and, unlike the Americas and Australia, there was no significant geographical barrier that would have prevented some making a "return" over the last 40,000 years.

[mc2fool]

The lack of Neanderthal DNA in sub-Saharan African groups indicates that the descendants of the Out-of-Africa groups didn't -- in the 40,000 years following the last possible interbreeding with Neanderthals -- spread back into sub-Saharan Africa and promulgate their acquired Neanderthal DNA there. Some, sure, but not in any significant numbers at least.

Actually, I guess it's possible that they did but the Neanderthal DNA conferred some evolutionary disadvantage that made those lines with it in Africa die out.

But it's difficult to imagine what environmental challenge would select against them that would be unique to sub-Saharan Africa (a big place with a very wide range of environments) that wouldn't also have existed somewhere else on the planet. Yet Neanderthal DNA is universally present in all non-sub-Saharan African populations....

[9873210]

[
But it's difficult to imagine what environmental challenge would select against them that would be unique to sub-Saharan Africa (a big place with a very wide range of environments) that wouldn't also have existed somewhere else on the planet. Yet Neanderthal DNA is universally present in all non-sub-Saharan African populations....

Possibly a version of the "founder effect".

Suppose a small number of sapiens move into an area populated by neaderthals. Any interbreeding at that point will incorporate a certain percentage of neanderthal DNA. If nothing further is exchanges the neanderthal fraction would remain constant as the sapiens population grows.

In contrast to introduce a gene into a large established population you need to move large numbers of people, or there needs to be large selective pressure for that particular gene.

This is supposing no particular selective pressure for or against neanderthal genes, which is probably true for many individual genes which will just drift.

[9873210]

Agreed to a lot of that, except that it isn't exponential, and the sparseness of population groups and the difficulty of travel until recently makes it entirely possible that Leif Erikson's genes have never crossed with any Patagonian's, and even if they had those lines could have died out or remained within relatively small groups. Numbers aren't the only limiting factor nor the guaranteeing one.

The number of descendents is initially, on average exponential, for exactly the same reason the number of ancestors is. The lineages that die out are compensated for by the ones that grow faster. After a while the lines of descent overlap so long term the total number of descendants will resemble the logistics equation. But the slowing will only occur once a sizeable fraction of the local breeding pool is a descendant.

There is substantial evidence for trans-continental trade in pre-Columbian America, e.g. the Hopewell, Cahokia, Aztecs and Inca . If people are trading rocks, they are probably trading genes.

But of course none of that is proof. Descent from a single individual becomes more

[9873210]

Pre maturely posted and for some reason I can't edit.

But of course none of that is proof. Descent from a single individual becomes more diffuse over time. At this time I think the genetics is only telling us about the bulk flow of genes. This traces movement of large (relative to population size) numbers of people. The genetic evidence is very unlikely to be able to directly time the actual last common ancestor, probably something closer to the last common population, which could be much earlier.

[mc2fool]

The number of descendents is initially, on average exponential, for exactly the same reason the number of ancestors is.

Ummm...no, it's not the same. Everyone has only (at least until a couple of years ago) exactly two parents, no more no less, and so their number of ancestors is at the very most 2^n exponential, and of course will rapidly thin out to a lot less 'cos most people over most of human history have stayed in smallish communities and paired up with their first or second cousins or other not-too-distant relatives.

OTOH, people can have anything from zero to lots of children, and so their number of descendants is anything between none and potentially very much more than 2^n exponential. However, that's just mathematics and ignores the realities of disease, natural disasters, saber-tooth tigers and, the really big one until very very recently, infant mortality.

In fact, the human population has been fragile and is reckoned, overall, had little-to-no growth over most of its 200,000 year history, and has almost gone extinct several times. E.g. it's reckoned that one global climate change event 70,000 years ago knocked the world's human population down to as low as 3000. https://en.wikipedia.org/wiki/Toba_catastrophe_theory

At the beginning of the Neolithic, c10,000BC, world population was single digit millions (estimates vary!) and rose to 150-300m by 1AD but then remained overall pretty much the same for the next 1000 years. But then for the last 500 years or so population growth has been greater than exponential. https://en.wikipedia.org/wiki/World_pop ... _estimates

So, really, it's quite a complex story!

BTW, on trade, yep, there's compelling archaeological evidence for long distance trade well back, indeed much further so than the Americas "newcomers" you mention! However, from last I heard, it's believed that while the traded goods travelled a long way, the traders themselves didn't, with the goods making their journey in lots of relatively local hops. Of course, that doesn't invalidate your point at all, it just means that a trader's genes would have also travelled in short hops.

[colin]

mc2fool wrote

Agreed to a lot of that, except that it isn't exponential, and the sparseness of population groups and the difficulty of travel until recently makes it entirely possible that Leif Erikson's genes have never crossed with any Patagonian's, and even if they had those lines could have died out or remained within relatively small groups. Numbers aren't the only limiting factor nor the guaranteeing one.

If the figures I quoted from Rutherford's book are correct then Leif Erikson, assuming he has left surviving descendants is one of the ancestor's of every European alive today, we are all descendants of him as we are all descendants of Charlemagne, Patagonia is populated by people who all share European descent to varying extents, there are even Romany Gypsies selling sprigs of the closest thing they have there to heather. I have met them in Puerto Mont. The indigenous natives who survived contact with the Spanish colonizers have been having children with people of Spanish descent for so long that I would find it hard to believe that there could be some enclave of indigenous people who do not share genes of European origin. That would just be a huge ethnographic story. So Leif Erickson's bloodline must stretch to Patagonia. They might have got there at the dawn of Spanish colonization as the Vikings were heavily into trading Anglo Saxon slaves on Spanish markets but there has been a constant influx of Europeans since the Spanish conquest at least and European Genes have spread throughout the surviving population of indigenous people.

9873210 wrote

This is supposing no particular selective pressure for or against neanderthal genes, which is probably true for many individual genes which will just drift

.
Some geneticists think that the percentage of Neanderthal genes in Europeans used to be higher than the 2-3% at present. It is believed that this Neanderthal DNA is slightly mall adaptive and that European Homo Sapiens who possessed above average amounts were less likely to leave surviving children. Even today this DNA does not seem to be doing us much good and is responsible for some Type 2 diabetes, Crohn's disease and weirdly smoking addiction.
Dr Alice Roberts pointed out on one of her programmes that though the average amount of Neanderthal Genes in Europeans is around 3 % we do not all have the same genes and some scientists think as much as 50% of neanderthal DNA may survive as it is spread throughout the population.