My principal
conjecture is that human expansion was a result of an evolving social
capacity. The hunting ban or the pride
are remarkably similar and generally revolves around several individuals and
their mates and children and essentially no more. This social space expanded about ten fold in
order for us to operate tribes and ultimately rural communities.
This capability
evolved somewhere and I suspect that it evolved easiest on several coastal
zones that allowed human concentration to be sustained year round. South Africa is one such zone and curiously
so is the Pacific North West. They were
not easily exploited, but it also drove adaptation to the intertidal. This opened up shell fish in particular as a
staple able to feed thousands living close by.
Other options
may well exist, but the intertidal is the easiest and most extensive. Thus an expanding capacity would drive
changes inside Africa which ultimately reached critical mass and exploded into
the rest of the world. In the process
predecessor populations were simply subsumed by the power of numbers.
Thus we have the
curious emergence of humanity itself about 200,000 years ago which appears to
be a plausible unique Boar Primate/chimp hybrid followed by back breeding
through the entire primate sub species that we are aware of. We may discover that a marine primate was
central to this evolution. We do have
some fossil evidence supporting such a finding.
I am been
aggressive projecting this Boar primate/chimp hybridization at 200,000 years
ago. It provides the solitary source of
the all-important mitochondria and it produces a flexible hybrid that will
naturally back breed and naturally select for important characteristics. This new man then evolved quickly as our
naked ape clearly adapted to both the ocean and the open plains.
The picture is
slowly becoming much clearer.
The mystery of
the human intelligence explosion
Over the past 200,000 years since Homo
sapiens evolved, something extraordinary happened. Somehow, we went from
being clever monkeys with stone tools, to being insanely brilliant masterminds
who use complex language, and control the planet with agriculture and
technology. How did we start the intelligence explosion that anthropologists
call the "human revolution"?
Perhaps one of the biggest mysteries in our
evolution is how humans developed symbolic culture, a very general catch-all
term that includes things like art, language, personal adornment, weapons, and
rituals like funerals. Symbolic culture is what sets humans apart from other
species, and yet it also seems to pre-date the emergence ofHomo
sapiens. We find
plenty of stone tools in Africa before 200,000 years ago, as well as evidence of fire pits
and art-making. OurHomo erectus ancestors were throwing spears and making
colorful paint from pigments thousands of years before we evolved.
So question is, when did these symbolic practices
start to define humanity? There is no easy answer, and we may never gather
enough evidence to come up with a definitive timeline. But there are two broad
theories about how it happened. One suggests humanity made a great cultural
leap forward roughly 80-60 thousand years ago, during the
"revolution" when humans hightailed it out of Africa and into
Eurasia. And the other suggests culture evolved gradually, in Africa,
over Homo sapiens' entire species lifespan.
The
Revolutionaries
The term "human revolution" is often
attributed to anthropologist Paul Mellars, who wrote in 2007 that this event was an "accelerated
episode of change" between 80-60 thousand years ago, right before the
Middle Paleolithic (or middle stone age) transitioned into the Upper
Paleolithic (or late stone age). For this reason, this change is also sometimes
called the Upper Paleolithic revolution.
At this point in time, the anthropological record
yields rich evidence that humans had gone way beyond their ancestors in terms
of technological sophistication. We had graduated from stone tools to bone (see
image below), and those tools were specialized for a wide range of activities
from tanning skins to hammering. Humans were fishing, transporting colorful shells over great distances (probably due to their
value as jewelry), heating pigments to create different colored paints, burning
areas near their homes to help desirable plants flourish, burying their dead
with special items, and painting elaborate motifs on cave walls.
There is also evidence that these new human
behaviors included larger groups of humans living together, in social groups
that were far more hierarchically organized than previous bands of
hunter/gatherers. At the same
time, these more structured groups were heading out of Africa into Eurasia,
bringing their culture with them. Eventually, these revolutionaries absorbed
or replaced the other human populations of Neanderthals, Denisovans
and possibly others in Eurasia.
[ this is
confirmation of my primary conjecture regarding the expansion of modern
humanity. It was all tribes – arclein ]
What could have caused the revolution? Mellars is
agnostic on this point, suggesting that it might have been a genetic mutation
that spread swiftly through Africa. Or it might have been "stimulated by
the economic and demographic pressures imposed by the rapid succession of
climatic and related environmental changes." This was a period of rapid
cooling, partly caused by the Mount Toba mega-volcano that erupted in Sumatra
about 74 thousand years ago.People might have been innovating because of
genetic changes, environmental ones, or both.
[ this is where
I differ. Simple hunting bands had their
own demands, but they limited social interaction to the band itself.]
Mellars compares the human revolution of 80 thousand
years ago to a more recent one called the Neolithic revolution that led to the
rapid development of agriculture and cities roughly 13-10 thousand years ago.
He and prominent anthropologist Ofer Bar-Yosef believe that this parallel with the
Neolithic is evidence that humans tend to develop in moments of cultural
acceleration. We go through phases of rapid innovation, punctuated by periods
of relative stability and even devolution.
Given that this is the case, they argue, it seems
likely that symbolic behavior was the result of a revolutionary change. That
also helps to explain why the fossil record shows an abundance of art and
complex tools in the Upper Paleolithic, all over the world.
###
The problem with the "human revolution"
account of events is that the past few decades have yielded more and more evidence that humans in Africa had symbolic
culture long before the so-called acceleration. Anthropologist Sally McBrearty explores this
evidence in an essay called "Down with the Revolution," (this builds off her earlier essay with Alison
Brooks called "The Revolution That Wasn't") where she fleshes out many of the assertions you
see in the figure above.
Based on new digs in Africa and the Middle East, we
now have evidence that humans were making paint and burying their dead in
symbolic ways over 180 thousand years ago, long before that
"acceleration." Long-distance exchange of items and shellfishing also
appear to have emerged before 100 thousand years ago. Of particular interest to
McBrearty is the fact that ostrich eggshell beads, used as personal adornments, date back 75 thousand
years.
In addition, as Alison George notes in a great
article in New Scientist, there's now
genetic evidence that a gene associated with human communication, FOXP2, might
have spurred human symbolic thought 170 thousand years ago. Archaeologist
Johan Lind told George that the "modern mind" might have actually
emerged as early as 500 thousand years ago, with our ancestor Homo
erectus. That would make sense, if we consider that Homo erectus used
tools and fire.
The problem, as McBrearty and many others point out,
is that evidence for human behavior in Africa is almost non-existent before 130
thousand years ago. At that time, sea level changes overtook some of the most
widely-studied coastal human settlements in South Africa and swept away
anything that had been deposited before that.
Related to that, evidence of the human revolution
advocated by Mellars is found mostly in Eurasia, not Africa. McBrearty suggests
that we have to integrate the very early evidence we do have from Africa into
the story of symbolism, which gives us a very different picture of gradual
development over hundreds of thousands of years, rather than accelerated change
over a few thousand.
There are also questions about whether what happened
in Eurasia should properly be called a revolution at all, since the sudden
shift in the anthropological record is the result of an influx of Homo
sapiens immigrants. "The word revolution implies a home-grown
development," McBreaty writes. "It does not imply that the
changes were the product of a population replacement." In other words,
it's not a revolution if a bunch of outsiders come in and convert the locals to
a new way of life. Those outsiders are just continuing to build on a culture
that started long ago, in Africa.
Or maybe they weren't just in Africa, after all.
Gorgeous and strange paintings discovered at El Castillo cave in Spain suggest
that the local Neanderthals were engaging in pretty sophisticated symbolism 40
thousand years ago, long before Homo sapiens arrived in that part of
Europe. The cave was occupied for thousands of years, and its many chambers are
decorated with animal drawings, handprints, and intricate, abstract designs
made of dots.
It's possible that our ancestors had the capacity
for symbolic thought long before Homo sapiens evolved. The hominins who
left Africa before modern humans did, like the Neanderthals' ancestors, may
have been developing symbolic behaviors in Spain, while Homo
sapiens did it in South Africa. That would explain El Castillo cave, as
well as why Homo sapiens was able to integrate the
local Eurasians into their cultures so easily.
But to return to the question we began with, the
answer may ultimately lie somewhere in between the revolutionaries and the
gradualists. It's likely that humans were gradually developing symbolic
behavior over 200 thousand years or more. But it's also possible that there
were several thousand years during which this symbolic activity was popularized
around the world, and became more sophisticated through cultural exchange with
Neanderthals, Denisovans, and other hominin groups who found each other in
various parts of Eurasia.
It's undeniable that humanity has gone through
periodic growth spurts, during the Neolithic revolution, and during the
Industrial revolution as well. But that doesn't mean we aren't also developing
key innovations during all those stable centuries too. A brilliant invention
(like, say,typesetting)
may be around for a long time before it explodes into popularity. Are those
moments revolutions, or just times when already-existing technologies become
widely fashionable?
Annalee Newitz is the editor-in-chief of io9, and
the author of Scatter, Adapt and
Remember: How Humans Will Survive a Mass Extinction.
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