It has been known since
Darwin's work
in the 19th century
that all of humanity (indeed all of life)
is on one family tree.
In other words, there existed in the past animals
who are common ancestors
of all humans now living.
What this page is about is when was the most recent
common ancestor of all living humans.
A number of new strands of evidence indicate it was
surprisingly recent, even within recorded history.
Common Ancestor of all living humans - There are trillions of these,
stretching from
the origin of DNA-based life
4 to 3.5 billion years ago
to a lot more recently
- perhaps even within historical times,
as we shall see.
Most of these are pre-human animals,
but the recent ones are human.
MRCA
Most Recent Common Ancestor of all living humans - This is a human,
perhaps even within historical times,
as we shall see.
Background reading
For ignorant reasons,
the origins of life and humanity
are often not discussed in schools,
so you may need some background reading
before you start:
Speciation
- There is no such thing as the "first" human.
The MRCA is human
[O'Connell, 1995]
is wrong to suggest there is any doubt about the existence of CAs.
Their existence is certain, as is the fact that the
MRCA is human.
The existence of genes for human abilities (e.g. language acquisition)
in all humans is proof of this.
In general, there are a number of ways to
estimate the MRCA:
Genetics
- These suffer from the problem of only focusing on
the ancestors
from whom you have inherited DNA,
not all your ancestors.
You can descend from someone without having inherited their DNA
at a specific location on the genome,
or even without having inherited their DNA at all.
By focusing only on common ancestry of DNA that gets inherited
at a specific location on the genome,
DNA studies push back the Common Ancestor much further than the
MRCA.
All CA's found in genetic studies will be much older than the MRCA.
Why DNA can't tell us the MRCA.
Archaeology
- The MRCA does not imply any sort of
population bottleneck at the time,
or any sort of "first couple".
The MRCA would have co-existed with a huge human population,
many of which
are ancestors of many, but not all, living people.
In the future, these too will become CAs
and there will be a new MRCA.
Since the MRCA keeps changing,
it is obvious that it does not have to exist at any important moment
in the fossil record.
The MRCA is a "statistical artefact",
and is unlikely to be significant
(or at all noticeable)
in archaeology.
Why Archaeology can't tell us the MRCA.
The above 2 methods can't tell us the MRCA.
The following 3 methods can,
and they all agree.
They all say the MRCA is in historical times:
Mathematical models
- These are better for looking at whether someone actually descends
from someone else, irrespective of DNA.
They suggest an MRCA in historical times,
as recent as c. 1200 AD,
if mating is random (we know that it is not).
The main limitation of mathematical models
is this issue
- the difficulty of modelling in any clean way
the complex, non-random mating patterns
caused by geography, population movement,
religion and social status.
To model the quirks of the history
and geography of the world, or just of the West,
you really need a computer simulation.
The other thing noted by mathematical models is that
not much longer before the MRCA,
everyone in the population
is either the ancestor of everyone alive today
or the ancestor of no one alive today.
Non-random mating would push the MRCA further back.
See following.
Computer simulations
- These can take into account all the quirks of local geography
and history.
These suggest that even with a high degree of
non-random mating,
the MRCA is still in historical times,
perhaps c. 300 AD.
If we restrict just to the West, rather than the whole world,
then the MRCA comes forward:
(a) because it is a smaller area,
and: (b) because
the West, with its constant intermarriage and migration,
is closer to a random mating model
than the world as a whole is,
with its extreme geographical isolation like populations in
Australia, the Pacific, etc.
Hence the West will have a lot more recent MRCA than the world.
See following.
History
- Genealogy, like my
Royal Descents page.
This has the problem of only focusing on
the ancestors for whom records survived,
not all your ancestors.
However, despite the sketchy records, it still provides
strong support for the suggestions above from mathematical models
and computer simulations
of an MRCA in historical times.
The huge number of
proven descents of people
from common European royal ancestry
in historical times,
when considered with the vastly greater number of descents
that must exist
but are not among the rare few that can be proven,
suggest strongly that everyone, in the West at least,
is descended from an MRCA in historical times.
They suggest, for example, that everyone in the West
is descended from
Charlemagne,
c. 800 AD.
The conclusion of the above lines of evidence
is the following.
The world
It would seem possible that, even with a lot of geographical
separation, the MRCA of the entire
world is still within historical times,
3000 BC - 1000 AD.
We pick them as an example because
they left proven descents for centuries,
so it seems likely their descents
did not die out,
and they are ancestors of
some people alive today.
Hence
probably ancestors of
all people alive today.
The interbreeding world
The MRCA of almost all of the world
is in historical times,
quite possibly in classical times, even AD.
By "almost all" I mean over 90 percent of the world,
including all of the West, almost all of Asia,
and most of Africa.
Only cases of extreme
geographical isolation could prevent this
being the whole world,
leaving some aboriginal populations out of this recent family tree.
If populations were truly geographically isolated
for thousands of years
then the MRCA of the entire world
may be thousands of years ago.
Though even that is not certain since there has been
a certain amount
of interbreeding
since these populations were re-contacted in the last few
hundred years.
And we only need a small amount of interbreeding to get everyone
descended from Europeans.
That is, we just need to get them genealogically descended,
even if it doesn't show in the DNA
- even if the European DNA has been swamped by the rest.
Quite likely almost everyone in the world descends from
Confucius
(died 479 BC).
We pick him as an example
because he is the proven ancestor of some people alive today.
Hence
probably the ancestor of
all people alive today.
The West
The MRCA of the West
is in historical times,
quite possibly
as recent as 1000 AD.
Quite likely everyone in the West
descends from
Charlemagne
(died 814 AD).
We pick him as an example
because he is the proven ancestor of some people alive today
(for example, he is a proven ancestor of my children).
Hence
probably the ancestor of
all people alive today.
By the same reasoning, as well as
from Continental/pre-Norman figures like
Charlemagne,
quite likely
everyone in the West descends from
figures like:
These findings do not necessarily have any implications for our DNA.
To descend from someone
does not mean you necessarily inherit any DNA from them.
These findings
do not conflict with the idea that most or all of your DNA is inherited
from your local area.
Even if you do descend from the Ancient Egyptian Pharaohs,
that does not mean this can be detected in your DNA.
In fact, there may be
no evidence at all of these findings in humanity's DNA.
And yet the findings can still be true.
To see this,
imagine one Western European sailor blown off course in classical times, say 100 AD,
and landing in the
Caribbean,
with no way home.
He is not killed
but rather taken in by a tribe who need strong young men.
He mates with one of the native women and has children.
1/2 of their DNA is European.
The children mate with pure natives and have grandchildren.
About
1/4 (can be more or less, by chance)
of their DNA is European.
The grandchildren mate with pure natives and have great-grandchildren.
About 1/8 (more or less) of their DNA is European.
And so on.
By 1492, all of the Caribbean is descended from him,
but his DNA is extinct.
There is no evidence of his existence in the DNA of the living.
He is everyone's ancestor, but no one has his DNA.
In summary, we are interested here in genealogical descent, not genetic descent.
Quite likely
every Muslim in the world today
descends from the Prophet Muhammad (died 632 AD).
The Prophet
is apparently the proven ancestor
of some Muslims alive today,
hence probably ancestor of all of them.
Quite likely everyone in the West today
descends from the Prophet Muhammad (died 632 AD).
Muslim-Christian intermarriages, affairs, rapes and conversions
have often occurred through history.
Medieval Spain
would be fertile ground for such crossover.
One question is
whether any medieval Christian houses descend from Muhammad.
Even if no specific descent is known,
our model suggests there will be some.
The number of actual Muslim-Christian matings must be
much higher
than the few that we can suspect or prove.
With the Muslim population
of medieval Spain descended from the Prophet,
it is almost impossible for the Christian population
to stay separate.
All we need is a tiny amount of interbreeding
and fairly soon all the Christian population
are descended from the Prophet too,
and hence most or all of the West today.
Religious barriers can't seriously push back the MRCA,
only geographical barriers can.
It is interesting to think that
the World Trade Centre attack was almost certainly
some descendants of the Prophet
killing other descendants of
the Prophet.
Quite likely almost every Jew in the world today
descends from the Prophet Muhammad (died 632 AD).
By the same logic, there were Jews in medieval Spain,
and it's hard to see them staying separate from the gradual
descent of all of Muslim and Christian Spain from the Prophet.
Again, all we need is a tiny amount of interbreeding for this
to happen.
And later the Jews of Spain
were expelled,
and are probably hence the ancestors of much or most
of the world's Jews today.
It is interesting to think that
every Palestinian suicide bombing attack on Israel
is almost certainly
some descendants of the Prophet
killing other descendants of
the Prophet.
Of course ultimately
the whole world
will descend from the Prophet.
In fact, this may already be true!
If you have a line of descendants that doesn't die out,
eventually you are the ancestor of the whole future world.
Through this,
you affect all future world history.
If the humblest Ancient Egyptian peasant
had done anything different
(even just had sex 5 minutes earlier),
there would have been no
Jesus, no St.Paul, Muhammad,
Copernicus, Newton, Darwin,
Marx, Freud, Lenin, Stalin,
Hitler or Mao.
There would have been no
Christianity, Islam,
Marxism, Freudianism, communism,
Nazism or Maoism.
These are belief systems,
collections of beliefs accepted due to
charismatic founders.
There would still have been
Copernicanism, Newtonianism and Darwinism.
- These are discoveries
about the world,
that would be made no matter what.
Science would still be here,
but the religions and totalitarian systems would be different.
There may have been no Holocaust.
There may have been global nuclear war.
Humanity might be extinct.
Finally, remember that all these CAs are moving targets.
These CAs are defined
relative to the world
in the state it is in now,
i.e. in 2000 AD.
If we were living in 1000 AD,
we would be talking about a completely different MRCA.
Similarly, someone alive today (maybe you, maybe me)
is an MRCA of the world at some future date.
"Mitochondrial Eve" is only
defined relative to AD 2000.
In 1000 AD there was a different Mitochondrial Eve,
and in 1000 BC there was a different one still.
Ronald Fisher
in
The Genetical Theory of Natural Selection
(1930)
in Ch.6
estimates
that only a few hundred years ago, everyone in Britain, say, would have
the same ancestors (everyone who left descendants).
"The ancestry of members of the same nation can differ little beyond the last 500 years".
Richard Dawkins in
River Out of Eden (1995)
in Ch.2
estimates that two random British people would probably have an MRCA
"no more than a couple of centuries ago, probably well after William the Conqueror".
Richard Dawkins does however probably get it wrong in
The Magic of Reality (2011).
In Ch.2
he says:
"if you happen to come from England, our most recent shared ancestor probably lived only a few centuries back.
If you happen to be a native Tasmanian or a native American we'd have to go back some tens of thousands of years
to find a shared ancestor. If you happen to be a !Kung San
of the Kalahari Desert, we might have to go back even further."
This seems inaccurate.
This work suggests it would be more recent than "tens of thousands of years".
Comments on Royal Descent
- "probably sixty percent or more of the American people are descended from kings"
Roberts
also says
"Anthropologists claim everyone on earth is a 40th cousin"
(i.e. any pair of 2 people
can find at least 1 common ancestor since about 800 AD).
In his calculations, the odds of any one of your ancestors in 1600 AD
not descending from Edward III might be
quite high (something like 0.999)
but the odds of all of them not descending from Edward III
would be tiny (something like 0.99910000).
He concludes that almost every modern English person with predominantly English ancestry descends from Edward III,
and Edward III probably has something like 100 million descendants across the West.
Descents from Jesus:
The conspiracy theory of a
Jesus bloodline
(an exclusive group of descendants of Jesus)
makes no sense.
The problem is not the suggestion that Jesus had children.
That could easily be true.
The problem is the idea that his descendants could be an exclusive group.
As
Steve Olson
said in 2006:
"If anyone living today is descended from Jesus, so are most of us on the planet."
Descents from David:
Evolutionary biologist
Yan Wong, 22 Aug 2012,
discusses MRCAs in the context of the Biblical story that
Jesus
was from the
"House of David".
The Bible shows two contradictory genealogies.
There is a further contradiction in that it claims Jesus was not Joseph's son.
And there is no evidence outside the Bible for the existence of
David.
But leaving all this aside,
Yan Wong
points out that if we assume David existed around 1000 BC,
more or less everybody in
the Holy Land
around 1 BC would descend from him.
Media coverage
There has been media coverage of my work on MRCAs. See various links in:
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