This item gives us a great up to date review of the present state of
our knowledge of human prehistory. I am pleased to see that modern
humanity emerged fully some 60,000 years ago. Thus it is completely
reasonable that the first emergence of civilized man arose
approximately 40,000 years ago allowing a solid 20,000 thousand years
of internal development. This first emergence exploited the coastal
plain and the tropical lowlands in particular and most likely
throughout SE Asia. As posted in the past, this conjecture is
obviously speculative and ultimately needs a major site corroboration
which may simply be never forthcoming because such evidence was
removed.
What has been critical to my argument is the establishment of just
when humanity could first have established civilization itself. This
turns out to be not sooner that 60,000 years ago. Yet they only
began then. Twenty thousand years is reasonable for the actual
development itself. Then we ask the question; if not why not? We
have since done it all inside of 9000 years after flubbing two
plausible opportunities to get it right 2000 and 3000 years ago and
possibly others more recently.
Thus we might agree that the capacity could have existed 40,000 years
ago and that it plausibly happened. What we are missing is the
history of a totally modern society such as we are presently evolving
between 40,000 BP through 13,000 BP, a period of 27,000 years of
modernity living on the coastal plains. That was ample time to
accomplish everything we imagine possible today before they arranged
to trigger the crustal movement that ended the Great Ice Age.
Our problem is to locate actual evidence that they overlooked when
they evacuated Earth. Some has been picked up on but not understood
and simply too scant as yet.
Beyond all that, human evolution is coalescing globally through
accelerating hybridization that will in time eliminate any aspect of
genetic isolation. We have now come to realize that the neanderthals
were genetically overwhelmed by our burgeoning populations and that
this happened to other genetic distinct groups also. In the tribal
environment this has always meant elimination of competing males
while preserving the women of child bearing age. Thus a burgeoning
population ultimately absorbs a smaller population quickly. That is
what ultimately happened to much of the Indian population of the
Americas.
A Bone Here, a Bead
There: On the Trail of Human Origins
A CONVERSATION WITH
CHRIS STRINGER
Origins of Modern Humans: John Noble Wilford interviews the
paleoanthropologist Chris Stringer of the Natural History Museum in
London.
By JOHN NOBLE
WILFORD
Published: July 16,
2012
Who are we, and where
did we come from? Scientists studying the origin of modern humans,
Homo sapiens, keep reaching deeper in time to answer those questions
— toward the last common ancestor of great apes and humans, then
forward to the emergence of people more and more like us in body and
behavior.
Their research is
advancing on three fronts. Fossils of skulls and bones expose
anatomical changes. Genetics reveals the timing and place of the Eve
of modern humans.
And archaeology turns
up ancient artifacts reflecting abstract and creative thought, and a
growing self-awareness. Just last month, researchers made the
startling announcement that Stone Age paintings in Spanish caves
were much older than previously thought, from a time when
Neanderthals were still alive.
To help make sense
of this cascade of new information, a leading authority on modern
human evolution — the British paleoanthropologist Chris Stringer —
recently sat for an interview in New York that ranged across many
recent developments: the evidence of interbreeding between
Neanderthals and Homo sapiens; the puzzling extinct species of little
people nicknamed the hobbits; and the implications of a girl’s
40,000-year-old pinkie finger found in a Siberian cave.
Dr. Stringer, an
animated man of 64, is an anthropologist at the Natural History
Museum in London and a fellow of the Royal Society. But he belies the
image of a don: He showed up for our interview wearing a T-shirt and
jeans, looking as if he had just come in from the field.
A condensed and edited
version of our conversation follows. In it and in a new book, he
describes a new wrinkle to the hypothesis of a recent African origin
of modern Homo sapiens. His ideas may light up more debate in a
contentious science.
First of all, would
you explain the title of your new book?
Yes, the title is
“Lone Survivors: How We Came to Be the Only Humans on Earth.” And
this comes from the fact that if we went back 100,000 years, which is
very recent, geologically speaking, there might have been as many
as six different kinds of humans on the earth. All those other kinds
have disappeared, and left us as the sole survivors.
You wrote that in
1970, when you started doing research in this field, the origin of
modern humans was hardly recognized as a topic worthy of study in
science. What has changed since then?
It’s been a
fantastic time to be involved in the field, and even when I was
writing this book in the last two years, I had to regularly go back
and rewrite things I thought I’d finished with, because new
developments were coming up all the time. In 1970, for some people,
there was no single origin of modern humans: We evolved globally, all
over the world. There was a view that in the different regions an
earlier species, Homo erectus, evolved relatively seamlessly to
modern humans. This idea was known as multiregionalism.
The argument went that
we remained one species throughout that evolutionary process, because
there was interbreeding among the different populations. It meant
that the Neanderthals in Europe, for example, would be the ancestors
of modern Europeans; Homo erectus in China would be the ancestor of
modern Asians. And Java Man would be a distant ancestor of modern
Australian aboriginal populations.
What we have seen
since then is a growth in the fossil record, in our ability to date
that record and to CT-scan fossils and get minute details out of
them. DNA studies have had a huge impact on our field. We now have
the genomes of Neanderthals and of these strange people in Siberia
called the Denisovans.
Speaking of DNA, what
about the African Eve? This established an approximate date for the
genetic origin of modern humans, in Africa. As a leading advocate of
the recent African origin, in contrast to the multiregional model,
did you believe this settled the debate?
To be honest, it’s
not been totally resolved, but the Mitochondrial Eve publication of
1987 was a key moment. Up to then, a few of us were arguing for a
recent African origin from the fossil and archaeological evidence.
But the evidence was pretty skimpy, and the majority opinion was
against our view.
When this new genetic
technique appeared, it seemed to give clarity to the picture. Here
was an independent bit of data, from our mitochondrial DNA, inherited
through females, suggesting we originated, all of us, all over the
world, from a single ancestral population that lived in Africa maybe
200,000 years ago.
I came to this
conclusion gradually, starting with the Neanderthals. They were the
best-known ancient humans, and there was a view that they were our
ancestors. I tested that model in my Ph.D. research, and I concluded
the Neanderthals did not make good ancestors of modern humans, even
in Europe, where we had the best data. So gradually my search moved
from one region to another, to see where the evidence best fitted the
idea of our origins.
It turned out that
Africa was the place that had the oldest fossils of modern humans.
Africa, for me, was the only place that showed a transition from
archaic to modern humans.
In your book you
propose that there was not one place in Africa where modern humans
originated.
Earlier, influenced by
the mitochondrial DNA data, I felt there was one place in Africa, a
sort of garden of Eden, where we evolved, where we changed
behaviorally and physically to become modern humans.
But the story is much
more complicated. Even the DNA data show that essentially each of our
genes has a separate evolutionary history. And so, when you look at
the total picture, including the fossil data and archaeological data,
there is no single spot in Africa that seems to be the place for our
origins genetically.
The story is dominated
by East Africa, because that’s the area that has the best
preservation of the fossil record. You could say southern Africa is
giving scientists the best record of behavioral evolution. They are
finding evidence pretty early of processing marine resources, the use
of red ocher for symbolic purposes, self-adornment with shell beads.
In my view, different
parts of Africa were important at different times, to distinct human
species, and this was being controlled by the climate. Africa is a
huge place influenced by many different factors: the Mediterranean,
the North Atlantic, the South Atlantic, the Southern Ocean, the
monsoons coming off the Indian Ocean. At different times this would
have produced good areas for humans and bad areas.
Populations in
different areas would have flourished briefly, developed new ideas,
and then maybe those populations could have died out, even — but
not before exchanging genes, tools and behavioral strategies. This
kept happening until we get to within the last 100,000 years, and
then finally we start to see the modern pattern behaviorally and
physically coalescing from these different regions to become what we
call modern humans by about 60,000 years ago.
Previously, the
splendid cave art of Europe influenced the view that modern behavior
began there some 40,000 years ago. How firm is the new interpretation
that Homo sapiens developed modern behavior as well as modern anatomy
in Africa?
There were remarkable
things happening in Europe at least 40,000 years ago, with the
painted caves, with flutes, with the statuettes and so on. But the
seeds of that revolution were sown in Africa more than 100,000 years
ago. I would argue that when modern humans came out of Africa, say
60,000 years ago, fundamentally they were behaviorally modern. They
took that into Europe. They took that into Asia and into Australia.
So there was no single revolutionary event in Europe; this was
something that was in modern humans when they came out of Africa, and
the ones who stayed behind as well.
How does the discovery
in Indonesia, on the island of Flores, fit in with current thinking
about human migrations and lineage? Are the so-called hobbits really
members of our genus Homo?
The hobbit, Homo
floresiensis, is a really challenging find for everyone. There’s
still a minority of scientists who don’t accept that it is a
distinct human species; it’s some kind of a weird, maybe diseased
form of modern human. But I think it is a genuine distinct form, and
actually a very primitive form.
It’s either derived
from a very primitive form of Homo erectus, maybe similar to the ones
at Dmanisi in the Republic of Georgia, or it’s evidence of an
earlier Africa exit, maybe before two million years ago, by something
that’s pre-erectus that somehow got all the way over to the Far
East and survived there in isolation, evolving for more than a
million years. It’s an extraordinary story, if that’s true. And
again, further evidence of how little we know about much of Asia in
terms of this story.
The more you learn,
the more fascinating the subject becomes.
In your earlier
career, you concentrated on Neanderthals. Do you now accept the new
evidence of Neanderthal-Homo sapiens interbreeding, which seems to
establish that we are more than 2 percent Neanderthal?
This is one of the
remarkable bits of news of the last couple of years. We’ve had the
genomes of Neanderthals reconstructed, and yes, indeed, it shows that
people outside of Africa have, on average, about 2.5 percent of an
input of Neanderthal DNA in them. And, of course, it’s led to a
rethinking of our relationship with them; clearly there was viable
interbreeding.
We don’t know the
circumstances. Maybe a parsimonious view is that there was a single
interbreeding period when modern humans came out of Africa. They met
some Neanderthals in the Middle East. There was some interbreeding,
under circumstances we don’t know yet, and that input of
Neanderthal DNA was then transferred as those populations spread to
Europe and to China, down to New Guinea, into the Americas; they took
that bit of Neanderthal with them.
Archaeologists have
found evidence that Neanderthals and Homo sapiens occupied the same
caves in Israel. Could this have been an interbreeding contact?
Western Asia becomes a
critical area for this possibility of interbreeding. It could have
been 25 Neanderthals mixing with 1,000 modern humans. It doesn’t
have to be a lot of Neanderthals, but clearly there might have been
interbreeding somewhere like Israel or Lebanon or Syria — all
possible places where we know Neanderthals lived, and at times modern
humans also lived.
There’s also a view
that the interbreeding was more widespread, but that either cultural
or physiological factors limited the successful births. For example,
we know that the pelvic shape of Neanderthal females is different
from the pelvic shape of modern human females. If a modern human
female was giving birth to a hybrid baby, part Neanderthal, could
there have been obstetric problems? We don’t know the circumstances
of these encounters: if it was a peaceful mixing and merging of these
people, or if the circumstances were violent.
Just who were the
Denisovans?
It’s an
extraordinary discovery. Two or three years ago I vaguely knew there
was an archaeological site in Siberia called Denisova Cave. And then
a few teeth, a finger bone have produced a really high-quality genome
now that’s posted on the Web site of the Max Planck Institute
for Evolutionary Biology in Leipzig, Germany. The preservation
of the DNA is exceptional, and well beyond anything we have from
Neanderthals. It seems these Denisovans were related to the
Neanderthals, an early branch off the Neanderthal line.
We know a lot about
the Denisovans genetically, but physically we know very little about
them. These fossils are so fragmentary. The even more remarkable
thing is they are only known from one site in Siberia, and their DNA
turns up in people only in really one region today — not in
Siberia, or Asia, but down in Australia and New Guinea. That’s
extraordinary.
This is difficult to
explain, because we thought that the ancestors of the Australian
Aborigines and New Guineans must have got to their regions through
southern Asia. Somewhere in Southeast Asia is the most likely place
they would have had interbreeding with the Denisovans. That also
implies the Denisovans were not just in Siberia; they must have been
a widespread group.
This raises one more
question: Could we ever clone these extinct people?
Science is moving on
so fast. The first bit of Neanderthal mitochondrial DNA was recovered
in 1997. No one then could have believed that 10 years later we might
have most of the genome. And a few years after that, we’d have
whole Denisovan and Neanderthal genomes available. So no one would
have thought cloning was a possibility. Now, at least theoretically,
if someone had enough money, and I’d say stupidity, to do it, you
could cut and paste those Denisovan mutations into a modern human
genome, and then implant that into an egg and then grow a Denisovan.
I think it would be
completely unethical to do anything like that, but unfortunately
someone with enough money, and vanity and arrogance, might attempt it
one day. These creatures lived in the past in their own environments,
in their own social groups. Bringing isolated individuals back, for
our own curiosity or arrogant purposes, would be completely wrong.
In the introduction to
your book, you list the kinds of questions you’re always getting
from people. One of them will be the closing question: What is the
future of human evolution?
That’s a tough one
to answer. There’s a lot of data, not my research, but mainly
geneticists have been working on this, and they’ve showed just how
many genetic changes there have been in the last few thousand years
in the human genome. And this is because we’ve undergone great
changes with urbanization, with agriculture, very big changes in
lifestyles. And this has influenced our genetic makeup as much as
living in the Paleolithic had done. We’ve seen, if anything, an
acceleration of genetic changes in humans due to these lifestyle
changes. So, I think human evolution has been going on quite rapidly
recently, and it’s going to carry on.
Not everyone agrees.
My colleague in London, Steve Jones, has argued essentially that
evolution has stopped in humans because we are in control of it. We
have medical care. Nearly everyone reaches reproductive age. Everyone
has enough food and water. So natural selection has been nullified in
humans. I disagree with him because, of course, there are still a lot
of people in the world who don’t have the best medical care, who
don’t have enough food and water. Think of the impact of AIDS in
Africa.
So selection is still
operating on many human populations just as much as it ever has done,
really. Also, all of us probably have 50 mutations in our DNA
compared with our parents. So that’s going on every generation as
well. We are still evolving. We will continue to evolve.
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