According to scholar Richard G. Klein (see video below), by about 50,000 years ago, a major change had occurred in human behavior (described as behavioral modernity, the great leap forward, or the mind’s big bang).  Suddenly, the number of artifacts humans could make had exploded, suggesting an increase in behavioral plasticity.

According to Klein, before 50,000 years ago, virtually everyone thought you could only make artifacts out of stone. After 50,000 years ago, they suddenly realized you could use bone, ivory, antler or shell.

Before 50,000 years ago, people didn’t spatially organize their living areas.  In other words, they would cook, clean, eat, etc, everywhere in their living space.  After 50,000 years ago, people suddenly realized they could divide their space into a cooking area, and eating area, a cleaning area, etc.

Before 50,000 years ago, humans buried their dead only to dispose of the corpse. After 50,000 years ago, burials suddenly became ritualistic and ceremonial.

Before 50,000 years ago, humans didn’t produce art.  After 50,000 years ago, art becomes common.

Before 50,000 years ago, humans didn’t fish and their hunting techniques were less efficient.  After 50,000 years ago fishing becomes common and hunting becomes efficient.

How do we explain this?  It’s not as if we suddenly evolved into a new species 50,000 years ago.  Indeed in another youtube video, Klein tells some university students that if a human from a 100,000 years ago walked into the university lecture hall, you wouldn’t notice anything different about them.  The only you thing he said might notice is that person’s really well built.


However Klein believes that sometime around 50,000 years ago, a genetic mutation occurred that suddenly made humans so much smarter allowing them to rapidly spread out of Africa and replace all the other living “humans” so completely.

Klein is not the only one who believes something like this. Geneticist Spencer Wells says in his TED talk (see the 14 minute mark of video below), that from 1 million years ago, to about 65,000 years (a similar date to Klein’s 50,000 BP, though some scientists put the date as early as 80,000 years ago), there’s a long period of cultural stasis where stone tools and other artifacts shows virtually no improvement.  Then suddenly after 65,000 years ago, the archeological record shows radical improvement.  Wells believes this was because fully complex language began to appear around that time.

In a previous post, I noted that the kind of stone tool Homo Erectus made indicated an IQ of 55, and yet according to Wells, the quality of said tools did not improve until after 65,000 years ago.  Does that imply that big brained anatomically modern humans still had an IQ of 55?  Why did brain size increase so dramatically if it wasn’t adding anything to our intelligence and if it was adding something to our intelligence, why weren’t our tools improving?

It’s almost as if brain size was increasing in anticipation of that sudden mutation that would suddenly allow us to use it, like a sudden flash of lightening.  Of course evolution can’t anticipate, unless you believe in intelligent design.  As one documentary put it, it was like humans were suddenly touched by the hand of God.  As an atheist I reject all that.

The question remains: what was the average IQ of  anatomically modern humans (AMH) who were not yet behaviorally modern?  I have previously estimated that the average IQ of Homo Erectus to be 55 and that the most primitive contemporary human races (i.e. bushmen, pygmies, australoids) have a genetic IQ of 70.  If we assume the early AMH people were half way between Erectus and Bushmen, that would imply an IQ of 63, and that this behavioral modernity mutation added 7 points.

But 7 points doesn’t sound like enough to produce this huge cultural leap scientists describe.  So either Homo Erectus has a much lower IQ than I think or bushmen have a much higher IQ than I’ve given them credit for, or early AMH was much closer to Erectus than Bushmen, despite their modern brain size.

Of course there’s also the possibility that behavioral modernity was caused by a mutation unrelated to intelligence (perhaps the position of the larynx in the throat changed improving speaking efficiency) or perhaps it was not a genetic change at all, but a breakthrough in cultural evolution.  In other words, we may have had fully human intelligence since 200,000 years ago when AMH first appeared, but it took until 65,000 years ago for culture to evolve to the point of symbolic behavior.  But 135,000 years is a long time for an ability to remain dormant.

Imagine if we took a bunch of modern normal babies from any human race and had the raised from birth in the jungle by chimps with no access to human language or culture.  Assuming some of them survived long enough to reproduce in the jungle, how long would it take for their descendants to show behavioral modernity?  I can’t imagine it taking 135,000 years.