
Family trees: Tracing the world's ancestor - selvan
http://www.bbc.co.uk/news/magazine-19331938
======
arethuza
_The Ancestor's Tale_ by Richard Dawkins looks at our ancestry right back to
the start of life:

<http://en.wikipedia.org/wiki/The_Ancestor%27s_Tale>

It looks at a list of different species and then considers the most recent
common ancestor we have with that species - fascinating stuff.

~~~
chris_wot
Someone has decided to downvote you. I really don't much like Dawkins (I'm a
Christian), but this is very interesting. I hit the update button - your
comment is a very worthy contribution to this discussion!

~~~
macspoofing
I suppose I understand, but his science books (which all of them are, save for
"God Delusion") are top notch. If you want to understand Evolution, there's no
better writer on the topic.

~~~
recycleme
I would consider The God Delusion a science book.

(It's really good btw. I would recommend it to any theist.)

------
T-hawk
This article makes the mathematical point, but deliberately ignores social
reality. Yes, 100 generations is sufficient time for the premise to be
possible, to fully propagate genes from every ancestor to every descendant.

But reality doesn't work that way. Human population groups breed within
themselves. Mating pairs are not chosen at random from the entire human
population. Consider all the remote groups that would have to be covered to
satisfy the assertion. Someone alive today would have to become a common
ancestor of every Lapp in Finland, every Aborigine in Australia, every Inuit
in Nunavut, every Maori of Polynesia, every Falklander, every North Korean,
and countless more groups that barely have any contact with the world
community, let alone interbreeding. (And maybe we'll actually launch a Mars
colony or interstellar generation ship, literally making it impossible.)

The article does mention this very offhandedly, inserting the clause "If
people in this population meet and breed at random". But that antecedent is
plainly false so the conclusions are not defensible.

~~~
brlewis
Note that the article never specifically talks about propagating genes, just
about being an ancestor. No matter how many generations you go back, there
will be at most 46 ancestors in that generation whose genes a descendant has,
and only one ancestor's mitochondrial DNA.

~~~
d2vid
Not true regarding 46 ancestors - chromosomal DNA is swapped between the
homologous chromosomes during meiosis:
<http://en.wikipedia.org/wiki/Meiosis#Prophase_I>

You are correct about mitochondrial DNA.

------
cs702
By the same mathematical logic, almost everyone in the US today is a
descendant of European royalty -- even people who are predominantly African or
Native American. Similarly, everyone in the US with primarily European
ancestry is a descendant of both Muhammad, the founder of Islam, and
Charlemagne, the so-called "Father of Europe."

These claims were made by an entertaining article written 10 years ago in The
Atlantic, "The Royal We," which covered the mathematical study of genealogy
and is a good companion to the BBC piece:
[http://www.theatlantic.com/magazine/archive/2002/05/the-
roya...](http://www.theatlantic.com/magazine/archive/2002/05/the-royal-
we/302497/)

~~~
bstpierre
I've actually traced my ancestry back to Charlemagne. It's an interesting
exercise. Some of my links are not very well substantiated, but the dozen or
two generations from Charlemagne forward are fairly well documented, depending
on how many of your ancestors were bastard children of some horny nobleman.
(Of course there are countless poor peasant farmers between now and then as
well.)

~~~
te_platt
I've also traced my ancestry back to Charlemagne. It's good fun but it's not
the iffy documentation that is the main problem. It's the milkman effect. In
talking with a researcher at a genetic genealogy center he said that around
10% of the population has a different biological father than they think they
do.

~~~
pacaro
I'd love to see this either substantiated or debunked - I've seen this claim
made and refuted many times, but have never found a truly reliable source.

~~~
Cushman
My recollection is that this number is based on a percentage of individuals
seeking paternity tests-- where obviously we would expect to see a much larger
number of false paternities showing up than in the general population.

------
lifeisstillgood
I always get confused here between "Eve" and MRCA.

AFAIK "Eve" is not what we are talking here - that is not as identifying one
person who is the ancestor of all living people, but that if we go back to the
time of David, then he, and 80% of everyone alive at the time (approx 1
million) MUST be ancestors of everyone alive now. That is some of his DNA and
some of everyone elses DNA at the time is in me.

That is pretty weird.

The other thing that gets me is that till agriculture, it seems human
population was stable at around 1 million. Then it started to grow to 1
billion by 1800. Freddie Mercury could sing to the whole population of earth
in three concerts.

~~~
Cushman
I don't think the difference you're talking about is real. "Eve" is
mitochondrial Eve, the most recent direct female-line ancestor-- the first
human every woman can say was her mother's mother's mother's et cetera.
There's a corresponding Y-chromosomal Adam; they probably lived 100-200,000
years ago, but not at the same time.

But of course if you're descended from her, you're descended from her parents,
and her mate's parents too; nobody came from just one person. Each one out of
our millions of common ancestors is an Adam or Eve by the popular definition:
Every human being alive is descended from them. If they had not conceived, _no
one_ currently alive would exist. There was never a biblically singular Adam
and Eve.

~~~
lifeisstillgood
So, the first person who was the MRCA-with female lineage only, ie the
earliest woman who was the female ancestor of all living people, was 100,000
years ago.

But the earliest ancestor (female / male / mixed lineage) was only 3000 years
ago.

(i.e. the first, had to have daughters only, the second, more recent could
have daughter then grandson then great-grandson etc)

So, 3000 years before we can say anyone definitely was the ancestor of all,
and there would be a lot of them. And 100,000 years before its female lineage.
Then pretty much everyone is a common ancestor, back to plankton. And
Dinosaurs!

~~~
Retric
More or less, except 3000 years ago travel was _far_ more of an issue. But,
somewhere in the ~2,500-30,000 years it's probably true.

Also, with a population of 1 million people a female line 'wining' is much
more likely than with a ~6 billion people population that probably will not
happen again for a vary long time without some awesome mutation.

------
mmcconnell1618
Mathematical proof why people get addicted to genealogy. They are almost
certain to find they are related to someone famous if they go back far enough.
It makes perfect sense why companies that provide genealogy research have no
problem finding customers. The lure of finding out that you are as awesome as
you thought you should be by way of royal bloodline, etc. is a pretty powerful
market force.

~~~
SoftwareMaven
My wife was playing around with the LDS Church's online genealogy tool and,
not surprisingly, found European royalty in her ancestry. I don't think I
quite succeeded at explaining that pretty much _everybody_ would have those.

For me, far more interesting than _who_ is in there is the _path_ things took
between me and that royalty.

------
itsadok
The point in the title is valid, but his answer to the original question seems
misguided to me: in the time of the bible the only lineage that mattered is
the paternal one. If your grandmother was King David's daughter that would not
make you his descendant. Not in the eyes of your contemporaries.

~~~
whatusername
Except that Judaism has a form of Matrilineality so King David/etc were
probably bad examples.

~~~
tezza
Matrilineality is mostly from the Talmud , a collection of Rabbinic opinion.

The Old Testament / Bible allows both parents to determine Judaism in the
child.

<http://en.wikipedia.org/wiki/Matrilineality_in_Judaism>

<http://en.wikipedia.org/wiki/Talmud>

------
wensheng
I don't think so.

People will stop having offsprings (and even sex) well before that because
they are immortal, even if they die, they can be resurrected because they have
copies. Provided, human race doesn't get destroyed by itself or AI.

------
msg
If you guys have not read Galapagos by Kurt Vonnegut (finished it this week),
you should.

Its about the evolution of the human species over the next million years
turning on very specific events in Ecuador in the year 1986, and the common
ancestor of all future humanity.

In his unique style, of course.

~~~
RockofStrength
That one is Vonnegut's sleeper masterpiece - the choice of narrator was
especially clever. How can you have a narrator narrate a million-year-spanning
story? Vonnegut figured it out.

------
tinco
The most important question is ofcourse, what do I have to do to be one of
those common ancestors and have my dna be part of every human alive? Is it
just having as many wives as possible like solomon and khan, or is there a
better strategy?

~~~
Cushman
Well, your number of children is linear, but your number of descendants is
exponential. For the CS students, what this means is that the number of
children you have personally, even assuming they all reproduce, rapidly
becomes immaterial next to the number of your descendants.

The only reason having more children might be beneficial is if it
significantly increases the odds that they personally, or their children
successfully reproduce. If you have some other way of boosting those odds --
say, by being a successful parent to a smaller number of children -- that's
just as good in the long run.

~~~
derekp7
But each generation only carries half the DNA of the previous one. So after 5
generations there is a vanishingly small chance that anyone after that will
still carry your DNA, with the exception of male lineage -- there you know
that the Y chromosome has made it through.

------
acchow
What is the probability that a descendent carries even at least one gene from
the "Most Recent Common Ancestor"?

The human genome has only 20,000 protein-coding genes (which comprise 1-2% of
human DNA). I'll be generous and use the 1% figure to assume that human DNA
has about 2e6 "genes" (protein-coding or otherwise).

After 100 generations:

Probability any one gene comes from MRCA: 1/(2^100). Probability any one gene
does not come from MRCA = 1 - 1/(2^100) Probability NO gemes come from MRCA =
(1 - 1/(2^100))^(2^6) = 0.9999999999999999999999999999495129020658552444536494

Probability at least one gene comes from MRCA = 5.05 × 10^-29

~~~
siganakis
I think that you have confused mutation with gene in your initial assertion.

There is probably only a few percent of variation between all of your 2^100
ancestors genomes (the majority of whom will be related), so protein coding
regions of your genome and your MRCA are actually likely to be very similar.

Now if that MRCA had a specific mutation, the chances of your inheriting that
specific mutation are probably low, but depend on that mutations prevalence in
the population as well as whether the mutation is deleterious or not.

100 generations is very few in terms of changes within the genetic make up of
a population under normal circumstances.

------
samspot
> That's why everyone alive in the Holy Land at the time of Jesus would have
> been able to claim David for an ancestor.

This really threw me for a while, as it seemed to be an obviously false
statement. Until I realized the author had switched contexts on me: Jesus
claimed male ancestry, but this statement is including ancestry from both male
and female lines. So it seems overall believable, however I still see many
provably false assumptions in this article.

* The population of the Holy Land was a constant 1 million people for 35 generations. Assumes no population growth. (false)

* No imigrants (false, see next bullet)

* No intermarrying with other cultures (false, because this intermarriage is often cited in the Bible as a reason people turned to other gods)

> More specifically, imagine the simplest case of a population of a constant
> size - say a million (the approximate size of the Holy Land at the time of
> Jesus).

I'm just quoting this to show that the author asks us to assume a constant
size population

I'm certain that there were thousands of people in Palestine that could have
claimed an unbroken ancestry from David. But based on all the flaws in this
article, I don't trust the assertion that everyone in the area can claim an
unbroken line (even including female ancestors).

------
placidex
Jon Kleinberg, Professor of Computer Science at Cornell University on the
pigeonhole principle: [http://edge.org/response-detail/2890/what-is-your-
favorite-d...](http://edge.org/response-detail/2890/what-is-your-favorite-
deep-elegant-or-beautiful-explanation)

------
est
> If you go back on average 1.77 times further again (35 generations) everyone
> in the population will have exactly the same set of common ancestors

The problem is, different people have different life span. And different
people can share the same parent.

And sometimes in extreme cases, father - daughter love?

~~~
reidrac
There's a method to estimate that:
[http://en.wikipedia.org/wiki/Most_recent_common_ancestor#MRC...](http://en.wikipedia.org/wiki/Most_recent_common_ancestor#MRCA_of_all_living_humans)

"Studies have used computer modelling to estimate that the MRCA of modern
humans lived between 5,000 to 2,000 years ago."

------
snowwrestler
Perhaps this person:

Person Who Will One Day Become Warlord-Ruler Of What Was Once Nebraska Born In
Omaha Hospital

[http://www.theonion.com/articles/person-who-will-one-day-
bec...](http://www.theonion.com/articles/person-who-will-one-day-become-
warlordruler-of-wha,27406/)

------
spindritf
I may be missing something but it doesn't seem necessarily true. Our last
common ancestor may have already died and we may not get another with all the
divisions that exist, or space travel that may happen (ie. we don't and won't
breed at random).

------
chris_wot
So in 3000 years we'll all be having sex with our relatives. Good to know!

~~~
gazrogers
We already are.

~~~
chris_wot
There's a cheery thought!

Seriously though, what about if you marry someone from a different country?
I'd imagine the chances are somewhat lower.

~~~
gazrogers
Never mind a different country - if you married someone from a different
species they're still related to you. The only difference is the number of
generations you need to go back to find the common ancestor.

~~~
lmm
Are we sure abiogenesis only happened once? Given how quickly life appeared
once the conditions were right, it doesn't seem too implausible that the
lightning strike might have happened in two different tidal pools on opposite
sides of the planet, and it seems just vaguely plausible that there would be
(bacterial) descendants of each that have no interbreeding in their ancestry.

~~~
derekp7
I asked this in a thread on Slashdot once, and got a really good answer.
Basically, there are a number of molecules that can have a left or right
chirality. These happened by random chance at the beginning instances of
abiogenesis, and were replicated faithfully since. So if it happened twice, a
number of those molecules (or larger structures) would be backwards. From a
macro perspective, things like the heart being on the left side, or the
direction of other internal organs (i.e. appendix on the right side). At the
molecular level, things like the spiral of DNA. There is some more information
in Wikipedia, under abiogenesis and homochirality.

------
lutusp
> In 3000 years someone alive today will be the common ancestor of all
> humanity

The title is very misleading. It's not true about any single person, unless
there's a species bottleneck with only one survivor, and then there's a
practical problem.

It would be more accurate to say that all those living 3000 years from now
will have their genetic roots in all those living in the present. But if that
had been the headline, no one would read the article.

How about this: "In 3000 years everyone alive today will be the common
ancestor of all humanity". True, but not very exciting.

~~~
hackinthebochs
The title is accurate. The article states explicitly that 3000 years ago the
common ancestor of all of humanity existed. It's just that 3000 years ago
wasn't the point where one and only one common ancestor existed; some 80% of
the population may have carried that distinction.

~~~
lutusp
> The title is accurate. The article states explicitly that 3000 years ago the
> common ancestor of all of humanity existed.

The title -- "In 3000 years _someone_ alive today will be _the common
ancestor_ of all humanity" -- is _not_ accurate. There was no single "common
ancestor", because modern humans owe their genetic inheritance to multiple
sources. This will be true in the future as well.

~~~
hackinthebochs
I'm not sure I understand the relevance of your point. If you're saying that
there is no _single_ common ancestor, but multiple common ancestors at the
timespan of 3000 years, then yes that is true. But that doesn't invalidate the
fact that any of them is the (perhaps better stated as "a") common ancestor.

~~~
lutusp
> But that doesn't invalidate the fact that any of them is the (perhaps better
> stated as "a") common ancestor.

The title clearly suggests a single ancestor, an individual.

------
TravisDirks
Very interesting! If I didn't misread, a better title would be "In 3000 years
almost everyone alive today will be a common ancestor of all humanity."

From the story: "In fact about 80% of the people at that time in the past will
be the ancestors of everyone in the present. The remaining 20% are those who
have had no children, or whose children have had no children, and so on - in
other words, people who were genetic dead-ends."

This puts a whole new perspective on the often quotes statistics about Genghis
Khan's progeny.

------
Claudus
So it seems that recessive traits, like blue eyes, will likely be bred out of
humanity in relatively short order.

At least until full blown reproductive genetic manipulation comes into effect.

~~~
aidenn0
You need to (re)read Mendel. Recessive traits and dominant traits stay at a
constant fraction within a population (absent selective pressures).

------
Shorel
We don't have conquerors and kings anymore, in most parts of the world.

The common ancestor would probably have to be the ancestor of a very
successful nation that would rule (a big part of) the world, and no current
world ruling nations let their governors reproduce at will, like they did in
the past.

Currently the world is full of Genghis Khan descendants, but also, there are
no Genghis Khan equivalents anymore.

Simply remember the Monika Lewinsky scandal.

------
Dn_Ab
What I am more interested in is: will someone who is alive in 3000 years be a
common ancestor of all humanity?

~~~
nihilir
Quoting the article: "And one can, of course, project this model into the
future, too. The maths tells us that in 3,000 years someone alive today will
be the common ancestor of all humanity.

A few thousand years after that, 80% of us (those who leave children who in
turn leave children, and so on) will be ancestors of all humanity. What an
inheritance!"

~~~
Dn_Ab
Heh =). But what I mean is something like, will there be someone alive in 3000
years that is about 2000 years old.

------
erikpukinskis
The concept is totally flawed, because the probability of inbreeding goes up
as you go back in the generations, so:

Probability your parents are the same person: 0

Probability one of your grandparents is the same person (i.e. your mom's mom
is your dad's dad's wife): very low

But then you get up to the point where you have 10k or 10m ancestors and those
numbers start to skyrocket.... especially given how relatively geographically
constrained we are.

So if you go back 3000 years, you'll have whatever 200 million (whatever the
global population was in 2000 B.C.) ancestors. But that number will be chock
full of "repeats". In fact you might only have 20 million "unique" ancestors
in that era.

You'd need to model migration to actually figure out when you could reasonably
expect that everyone would be somehow descended from you.

But even if you completely buy in to the premise of the article, they still
get the analysis wrong.

It's not that _someone_ will be _the_ common ancestor, it's that _everyone_ ¹
will be _a_ common ancestor of all humanity.

¹ who breeds and whose children breed, and their children breed...

~~~
saraid216
> It's not that someone will be the common ancestor, it's that everyone¹ will
> be a common ancestor of all humanity.

Yes, that's actually stated very pointedly in the article.

------
dkroy
Haha, I cannot believe that they could not get a better picture of the guy in
the article than they did.

Picture:
[http://news.bbcimg.co.uk/media/images/62401000/jpg/_62401882...](http://news.bbcimg.co.uk/media/images/62401000/jpg/_62401882_yanwong_bbc.jpg)

------
talaketu
It's a consoling thought for the childless... almost all the branches of the
vine end.

~~~
nihilir
I think you misread (or didn't read the entire article). The article states
that the majority of the "branches" will live as long as humanity itself. I am
currently childless and did not find this a consoling thought (quoted from the
article):

"In fact about 80% of the people at that time in the past will be the
ancestors of everyone in the present. The remaining 20% are those who have had
no children, or whose children have had no children, and so on - in other
words, people who were genetic dead-ends. [...] A few thousand years after
that, 80% of us (those who leave children who in turn leave children, and so
on) will be ancestors of all humanity. What an inheritance!"

~~~
hackinthebochs
No, it is true that eventually most branches will end. It's just on the
timespan of 3000 years, 80% of the population will likely be a common
ancestor. But if you extrapolate back far enough, there will be one and only
one. The only way branches can survive forever is if you assume that all genes
have essentially the same chances of survival. This obviously isn't true. Even
the smallest enhancement will quickly spread throughout the population.

I am curious when the most recent _unique_ common ancestor of humanity
existed. Would we consider him human now or something in between?

------
waterlesscloud
Or would have been, if genetic manipulation technology hadn't been invented.

------
InclinedPlane
Yes, and that person will be the inventor of some robot or other.

------
ktizo
Good to see a More or Less story on HN. For those who don't follow it, it is
basically either a UK current affairs show for the mildly autistic, or a
regular open university maths and economics lecture -
<http://www.bbc.co.uk/programmes/b006qshd>

~~~
polshaw
I really hate this trend for describing anything somewhat intellectual as
'autistic'.

~~~
lutusp
Yes, but psychologists love it -- it's bread on their table. Anyone
sufficiently to the right of the mean I.Q. can be diagnosed on the autism
spectrum, and be put into pointless therapy.

~~~
alanctgardner
I don't really understand this view of therapy. In my experience, it's
something you choose for yourself, because you recognize the need. The odds
that you receive a psychiatric evaluation against your will and be compelled
into therapy are amazingly slim. Especially for something like 'autism-
spectrum' disorders, where the majority of sufferers appear to be high-
functioning.

~~~
lutusp
> I don't really understand this view of therapy. In my experience, it's
> something you choose for yourself, because you recognize the need.

That would be nice, but it doesn't reflect reality. In schools, children are
frequently given autism spectrum diagnoses against their better interests, or
wishes, or the wishes of their parents (but not always -- sometimes parents
force these things on their children). But the patient's wishes are often the
lowest priority.

Ideally, people would volunteer for therapy solely on issues they choose for
themselves. But this isn't how clinical psychology works in modern times.
Schools have a vested interest in getting diagnoses, because special-education
funds are only available for those with a diagnosis.

The reason Asperger's is being abandoned is because it was applied in exactly
the way described above, until everyone realized it was a scam -- even the
therapists who benefited the most. Now it's slated for removal from the next
edition of the DSM, and further, the diagnosis criteria for autism spectrum is
being reworked to prevent another epidemic of nonsense diagnoses such as we
have just seen.

> The odds that you receive a psychiatric evaluation against your will and be
> compelled into therapy are amazingly slim.

On the contrary, it's an everyday occurrence, especially among children, who
aren't mature enough to realize that psychologists aren't doctors.

> Especially for something like 'autism-spectrum' disorders, where the
> majority of sufferers appear to be high-functioning.

Yes, and that is the present problem area -- bogus diagnoses, using vague
criteria that can be applied to nearly anyone, with obvious advantages to
everyone except the patient.

Mental health professionals, aware that autism spectrum diagnoses are out of
control and no longer have any connection to reality, have joined an American
Psychological Association task force charged with redefining ASD to stem the
tide of nonsense diagnoses. One of those behind the redefinition effort (Dr.
Fred Volkmar, director of the Child Study Center at the Yale School of
Medicine) says of the diagnosis surge, "We would nip it in the bud."

~~~
charlieflowers
"... Asperger's is being abandoned.... Now it's slated for removal from the
next edition of the DSM"

REALLY??! Wow. I sure _thought_ I was seeing a bunch of misguided hullabaloo,
but I'm surprised to see the "industry" itself is aware of it and addressing
it. Do you have a link or any kind of substantiation?

~~~
polshaw

        >Asperger’s syndrome... will be folded into a single broad diagnosis, autism spectrum disorder
    

^ FTA quoted as a source. It's not going anywhere, just re-labelling. There
are definitely things behind AS, it's certainly not all just 'hullabaloo',
even if a lot of cases might be.

~~~
lutusp
> It's not going anywhere, just re-labelling.

Not really. Two things are happening:

1\. Asperger's is being dropped as a diagnosis.

2\. ASD diagnostic criteria are being redefined with the specific aim of
reducing the number of diagnoses, to avoid another epidemic of nonsense
treatments of people who, apart from being intelligent, are otherwise normal.

Further reading: [http://www.nytimes.com/2012/01/20/health/research/new-
autism...](http://www.nytimes.com/2012/01/20/health/research/new-autism-
definition-would-exclude-many-study-suggests.html?pagewanted=all)

> There are definitely things behind AS ...

Yes, there certainly are. It's a gold mine for clinical psychology, because
anyone to the right of the mean population I.Q. can be diagnosed using the
present criteria, and because of this kind of abuse, it's being abandoned --
it's just too tempting to apply it to everyone. As one of its prominent
critics has said, "It's not an evidence-based term."

------
bluedanieru
Not if people alive today are still alive in 3000 years, which isn't terribly
likely but not wholly out of the question either.

~~~
lifeisstillgood
If they had kids today, and _then_ stayed alive, it would work out pretty much
the same. Except it would be fairly crowded.

------
jsemrau
You better hope it will be me!

------
treelovinhippie
Except that there is zero empirical evidence that the Bible figure "Jesus"
actually existed...

~~~
Tyrannosaurs
Given that the article makes it clear in the first sentence that this is about
more than the specific example of Jesus that's relevant how?

~~~
daleharvey
not mentioning Jesus was never a common ancestor to all people, even in the
bible.

Adam and Eve were (and I guess Noah?)

~~~
prawn
Also, from where did Jesus get his Y chromosome?

~~~
Tyrannosaurs
If you take the bible literally and assume that God is the father then is the
fact Jesus has a Y chromosome proof that God is a man?

