Reflections on the Work of Richard Klein

Richard G. Klein is a paleontologist and currently a professor at Stanford University. His work and his writings have done much to provide evidence for and to popularize the out-of-Africa theory of human evolution (known more scientifically as the recent single-origin hypothesis). This theory postulates that Homo sapiens—who have been anatomically indistinguishable from modern humans since about 150 to 200 thousand years ago—experienced a sudden and decisive change in behavior beginning around 50 thousand years ago; and concurrent with this change, Homo sapiens undertook a major migratory expansion out of Africa, soon swamping and extincting the similarly lineaged populations Homo neanderthalensis and Homo erectus, eventually becoming the overwhelming biological force we now can witness all around this planet. Over the last two decades, this theory has been supported by a growing accumulation of archaeological and genetic evidence, so much so that the theory is now accepted almost universally, and unless and until new contradictory evidence comes to light, the out-of-Africa theory must be considered as the definitive framework for describing recent human evolution.

Richard Klein seems to be a rare beast among modern scientists. He is plain spoken, more attracted to evidence and theory than to academic politics, and—note this especially—he tackles large scientific questions, not the mere trivialities that pad most curriculum vitae. In fact, the central question of Klein's work—what were the circumstances that prompted man to cross that great conceptual divide from simple primate to complex cultural being—stands as perhaps the most important unanswered question currently facing modern science. And if anyone has made more progress in shining a clarifying light on that question than Richard Klein has, I have yet to see it.

Much of Klein's summarization of human evolution can be found inside his two books The Human Career: Human Biological and Cultural Origins and The Dawn of Human Culture. However, for the purpose of the central question of Klein's work, there are two short and readily available presentations that encapsulate most of his essential ideas. The first is a lecture entitled Behavioral and Biological Origins of Modern Humans, delivered to the California Academy of Sciences in 1997. The second is a paper published in 2008, Out of Africa and the Evolution of Human Behavior, which can be regarded as an update to the evidence presented in the earlier lecture with Klein's views still essentially intact. These two presentations are both excellent examples of scientific clarity and honesty (so much so that many academicians might have a hard time recognizing them as scientific), and I urge anyone not already familiar with Klein's ideas to devote an hour or so to reading through these two documents—it will be time well invested on what is a fundamental and extremely important topic.

Although there are several scientists who have contributed to our understanding of the out-of-Africa theory, the area where Klein has most distinguished himself is in the painting of a clear, evidence-backed portrait of how sudden the Homo sapiens transformation was beginning around 50 thousand years ago and how overwhelming was its impact and expansive reach. Pointing to the fossil and archaeological evidence, Klein describes three distinct Homo-based populations that existed just prior to 50 thousand years ago: 1. the remnant lineage from Homo erectus, the successors from an earlier (over 1 million years ago) exodus from Africa, living primarily in the habitable areas of Asia; 2. Homo Neanderthalensis, a branch that had been occupying parts of Europe and the Middle East since around 400 thousand years ago; and 3. Homo sapiens, still in Africa and evolved into the anatomical form of modern humans by around 150 to 200 thousand years ago.

Although these three populations were geographically distinct and possessed distinguishing anatomical features, they were also remarkably alike in many fundamental respects. For one, they all had similar brain size, and perhaps more importantly, they all had similar behavior—behavior that could be captured in a single word … unremarkable.

Klein takes great pains to demonstrate that in site after site dating prior to 50 thousand years ago, there is no evidence to be found of form-based tools, artwork, jewelry, clothing, weaponry, etc., artifacts that soon will be making a sudden and explosive appearance on the human stage. He underscores that although Homo-based populations had certainly undergone behavioral changes since branching off from the other primates some seven million years earlier, the behaviors prior to just 50 thousand years ago were still far more comparable to older primate behaviors than to the modern behaviors that were about to emerge. Indeed, one can surmise that if an alien intelligence had visited this planet just prior to 50 thousand years ago, it would have found nothing remarkable about any of these Homo-based populations—these were simply primates scratching out their subsistence, indistinguishable bit players in the massive Earthly chorus of survival and procreation. Considering their meager numbers, and looking dispassionately at the fossil and archaeological evidence that Klein presents to us, we would have to conclude there was nothing in the circumstances of these Homo-based populations that would mark them as anything more than animal.

And then suddenly everything changed. And it has not stopped changing since.

The astonishing alteration first appeared near East Africa, right around 50 thousand years ago. In that location—and quickly expanding from there—you suddenly could find ostrich shell beads, form-based tools such as needles and awls, evidence of fishing technology, female figurines, clothing, burial displays, weapons galore. These suddenly innovative Homo sapiens soon began reaching into Europe and Asia, leaving behind a trail of newfound abilities literally everywhere along the path. They quickly overwhelmed and extincted the Neanderthals (Klein passionately describes the profound effect it had on him to see the sophisticated remnants of Cro-magnon culture (Homo sapiens) layered right on top of the less sophisticated artifacts of the Neanderthals, evidence of no intervening gap), and although the archaeological record is less complete in Asia, in part due to the ongoing interference of modern governments, it would appear Homo erectus also suffered a similar fate at the hands of these rapidly moving invaders. Their new mastery allowed Homo sapiens to boat to Australia by as early as 40 thousand years ago. Their unprecedented trapping, textile and construction techniques enabled them to inhabit colder climates, including Siberia, thus leading the way across the then dry Bering Straits and straight into the Americas. By ten thousand years ago, humanity had become so technologically adept it could begin trading its hunter-gatherer existence for domesticated animals and crops, and by six thousand years ago the species was building enormous civilizations and recording for posterity its burgeoning feats. By five hundred years ago, man could … well, you already know what man could do by then—just take a good look around.

It is hard to say which has been the more impressive: the suddenness of man's transformation, or the power of his planet-conquering reach. One thing is for certain: compared to the accomplishments of the previous 50 thousand years (or the previous 5 million years for that matter), these post-transformation exploits of Homo sapiens can only be described as stunning—stunning to an infinite degree.

But you need not take my word for it. Richard Klein has already laid out this entire tableau in exquisite detail, and he has seen all the evidence first hand.

As certain and insistent as Klein sounds about the immediacy and effectiveness of the Homo sapiens revolution, he sounds equally uncertain about the reasons why.

Klein has put forth—quite tentatively, I might add—what he describes as the most “economic” explanation for man's great leap forward, positing a sudden genetic mutation, one powerful enough to produce significant and immediate neurological impact, such as the kind that would induce rapidly spoken language. Against this thesis, it is commonly asserted within the academic community that the buildup to the Homo sapiens transformation must have been far more gradual than that, with various kinds of social and cultural evolutionary change—such as additional reliance on the nuclear family, an altered diet, theory of mind acquisition, a budding adaptability to change—all serving as the necessary forerunners to the dramatic upshot still to come.

Klein easily and quite rightly dismisses such counter proposals. In the first place, these explanations would need to be counted as tautological at best, since they are essentially positing that Homo sapiens behavior changed because Homo sapiens behavior changed. But even disregarding that obvious logical weakness, Klein demonstrates with the stubborn insistence of cold hard facts that such explanations are completely at odds with the fossil and archaeological record. Any slow evolutionary accretion of dramatically unique cultural and social conduct—including behaviors that would have been dependent upon a sophisticated use of language—could not have conceivably taken place without leaving behind a conspicuous trail of evidence. But what little (and mostly questionable) evidence has been offered in support of these evolutionary precursors ends up looking paltry and sparse next to the abundantly rich artifacts associated with the post-transformation epoch. Klein recognizes such vague explanations as not based upon the preponderance of evidence but instead as the type of fuzzy, non-committal solution generally favored by academicians—academicians who cannot be bothered by either logic or facts.

Klein is a scientist who insists on being bothered by logic and facts, which is why I suspect he is being so hesitant—for his explanation has myriad problems of its own.

The challenge of uncovering the catalyst behind Homo sapiens' sudden transformation must seem like a type of lock to Klein, one for which he has gauged its characteristics with a painstaking accuracy. He knows the contours of the many tumblers, has measured the keyhole for size, understands all too well the quick-releasing mechanism. He can dismiss the vague academic solutions as scarcely qualifying for keys at all—perhaps more than anyone else he can recognize the need here for something more tangible and immediate. Yet economically speaking, how many reasonable solutions actually exist? After all, Klein seems to be wanting to convince us—and to convince himself—is there not only one? A genetic mutation holds the promise of suddenness; a significantly altered neurological structure carries the potential for effective power. But in appealing to the genome and human brain for explaining mankind's astonishing transformation, Klein falls victim to that same fatal illness now plaguing the entirety of modern science—he has infused both genetics and neurology with an implausible human magic.

Intelligence, language, memory, numeracy, artistry, technological tool-producing vision—the scientific literature is now chock-full of genetic and neurological descriptions accounting for this entire host of impressive cognitive and behavioral skills. In genetic paper after genetic paper, you will find the microarray analysis protocols, the sequence-based samples, all lined up impressively along one side, and matched against that glorious detail you will find the list of unparalleled traits and attributes that have cast Homo sapiens as distinctively modern. Voilà, the genetic scientists all seem to say, and we break into terrific applause. But should an inquiring voice call out from the back of the room and wonder what connects transcription to observable behavior, what bit of mechanism links nucleotide to lyric poem, that voice will be greeted with an uncomfortably lengthy pause. Marvelous genetics here, astonishing behavior there, but in between … not one single connecting step.

The human brain has fared no better. In neurological paper after neurological paper, you will find entire albums of fMRI photographs, brilliant diffusion tensor pictures, all plastered across their pages in a technicolor glory, and matched against that vivid detail you will find the list of unparalleled traits and attributes that have cast Homo sapiens as distinctively modern. Voilà, the cognitive scientists all seem to say, and we break into terrific applause. But should an inquiring voice call out from the back of the room and wonder what connects resonance image to actual behavior, what bit of mechanism links synapse to third root of pi, that voice will be greeted with an uncomfortably lengthy pause. Vibrant images here, rational behavior there, but in between … not one single connecting step.

These connecting steps are not some mere trivial detail, not the mop-up work for a graduate student assistant; and yet even those scientists who can appreciate the importance of such linkages will speak as though their discovery is simply a matter of time. The secrets of human genetics and human neurology must emerge, these scientists all seem a little too willing to assure us, because in fact the scientific community has already accepted genetics and neurology as the driving force behind mankind's cognitive and behavioral splendor—no demonstration is apparently required.

But that state of affairs must seem a bit awkward for Richard Klein, whose mutation hypothesis, perhaps more than anything else, needs precisely that demonstration. Because without it, Klein's hypothesis does not even rise to level of relevance.

Intelligence, language, memory, numeracy, artistry, technological tool-producing vision—the scope and potency of that list can only be regarded as downright shocking, for there is no evidence any of these skills existed prior to 50 thousand years ago. The scene Klein lays before us is extraordinarily surprising, nothing at all like what might have been predicted. Its timeline defies every temporal characteristic of evolutionary history, its details contradict all expectation of species. So unique is the story of the Homo sapiens transformation that it might be more prudent to think evolution and biology must have played no role at all. In any typical approach to animal domains and behavior, genetic mutations would be expected to do their work only gradually, stepwise upon the species—their transmittal spread out across many generations, if not across entire ages. In any typical approach to animal domains and behavior, neurological restructurings would be expected to produce their impact only locally, specific to particular function—not fostering a cognitive reformulation extending from ear to ear.

But there is economy to consider after all, along with the confident assurances from modern science, and so rather than pursuing any unusual solutions to this preeminently unusual story, what could be more pragmatic than to turn to the typical approaches, and just give them a little anthropocentric boost.

In many respects, Klein's mutation hypothesis and modern science's genetic-neurological certainty are now the ideal soul mates, the perfectly matched couple. Klein's hypothesis receives from the promises of genetic and neurological science all the cognitive and behavioral power that his theory so desperately needs, while in turn, modern science gets from Klein's extraordinary anthropological story all the permission it could possibly want in order to study human genetics and neurology with an entirely different approach, with the license, with the justification—no, with the requirement—to ignore and break all the typical biological rules.

But tell me this: with each of these constructs leaning so heavily against the other, and resting apparently upon nothing else, why have we become so certain that they cannot collectively fall?

I think in some sense Richard Klein must already know all this, must feel the reasonable doubt somewhere deep within his tentative bones. I can admire his adamant courage, the plain-spoken insistence that the Homo sapiens transformational lock must have been opened only by a specific and tangible key, and I can understand his pragmatic desire to turn to the common and widely accepted mechanisms, resting comfortably on the assurances of modern science. But even Richard Klein must realize—must realize somewhere deep within his tentative bones—that in casting human genetics and the human brain into the role of Homo sapiens' transformational unlocking key, he must first bend and twist genetics and neurology all out of any recognizable, usable, or plausible shape.

An economic explanation—or should I say a scientifically magical explanation—is not worthy of Klein's extraordinary story.

So where does that leave us?

In recent years, I have been making the suggestion that there is an alternative way of looking at Klein's tableau, as well as looking at almost every facet of human behavior associated with it. I have become convinced that Klein's unusual anthropological story has in fact an unusual anthropological solution, a solution that defines—no, actually is—human atypicality. This solution is of course nothing like the cultural evolutionary theories favored by the vague academicians, and it is also nothing like the sudden genetic/neurological mutation hypothesized by Richard Klein. In the context of the entire out-of-Africa discussion, it must seem like an idea that comes from straight out of the blue, if not from straight out of nah-nah land. I understand all that, but must insist on making my suggestion all the same, because nearly everything in Richard Klein's peerless anthropological work points invariably in its direction.

My suggestion of course is autism. Autism is the key that fits that lock.

If we are going to understand the role autism must have played in man's great leap forward (and continues to play in man's ongoing transformation today), it becomes necessary first to see autism for what it truly is, a task made nearly impossible in recent years due to the debilitating grip of modern science. Modern science has already made its pronouncement upon autism, despite not knowing yet exactly what autism is—but never mind that, because the pronouncement has been made and the pronouncement is exceedingly grim. Autism is an illness. Autism is a developmental disaster. Autism is the incomparable tragedy of parents, the unspeakable burden of all mankind. If you listen carefully enough, you will hear inside that pronouncement an unflinching confidence and assurance—it is a confidence and assurance we have already encountered.

In a reversal of ironic proportions, that same collective mindset that has already accepted genetics and neurology as the undoubted catalyst behind all modern human behavior, now becomes the collective mindset demanding of autism that it be the foremost example of genetics and neurology gone bad. In autism study after autism study, you will find the fragmented copy number variants, the brittle axon-fiber connections, all lined up lugubriously along one side, and matched against that woeful detail you will find the list of traits and attributes that have cast autistic individuals as purportedly broken. Voilà, the autism scientists all seem to say, and we break into a respectful applause. But should an inquiring voice call out from the back of the room and wonder what connects fractured genome to unusual behavior, what bit of mechanism links fraying neuron to rhythmically flapping hand, that voice will be greeted with an uncomfortably lengthy pause. Research findings here, atypical individuals there, but in between … not one single connecting step.

The failure to supply these steps was, in the case of human intelligence, language, artistry and the like, an unfortunate circumstance, because along with the unjustified assurance that such steps would soon be found, it has prevented scientists from considering an alternative course. But in the case of autism, this same failure to supply these connecting steps, along with the undemonstrated certainty that autistic individuals are medically doomed—this practice has become the foremost example of unbridled cruelty. This practice denounces, without the first shred of understanding, nearly one percent of the human population as waste—the vast majority of whom must be working quietly and productively among us. This practice denounces, without the first effort towards acceptance, nearly the entire autistic population as pariah—when that population might be better described as mankind's deliverance. Modern science's confident assurance regarding autism is in fact a massive instance of scientific blindness, one that has rendered nearly the entire human population utterly oblivious to who autistic individuals actually are, and utterly oblivious to what they have amazingly done.

Autism can be accurately depicted without resorting to science's insistence on genetic disorder and neurological disease—without resorting to any cruelty. The key concepts are species, recognition and perception. Autism's fundamental description goes essentially like this: autistic individuals, to a significant degree, do not readily recognize or attach to the human species, and thus cannot easily organize their experiences or perceptions around that species and its members (as is the case for non-autistic individuals). In consequence, autistic individuals organize their sensory world instead by an entirely different form of perception, a perception engaged primarily by the symmetry, structure and pattern that inherently stands out from the surrounding, non-biological world.

It is that different form of perception—the autistic form of perception—that has launched Homo sapiens off the East African plains and straight into the modern world.

The Homo-based circumstances Klein describes from prior to 50 thousand years ago are circumstances typical of nearly every animal species. Prior to man's great leap forward, the human cognitive focus would have been directed towards survival and procreation alone, and human perceptual recognition and attachment would have been centered upon the species itself, exclusively upon its own members and behaviors. This intense species recognition and attachment is an evolutionary trait that must run deeply throughout the entire animal kingdom—biologists can see evidence of it nearly everywhere—and this trait of course has been critically important in helping hold species together, keeping their members gathered near sources of shelter, food and sex. The perceptual characteristics behind an intense intra-species focus help account for the behaviors of the genus Homo over many millions of years, and the same perceptual characteristics help explain also the behaviors of the species Homo sapiens for the largest portion of its existence. Intense species recognition and attachment is the primary reason that for a substantially long period of time—right up to 50 thousand years ago—man remained behaviorally indistinguishable from the rest of the animal world.

This intense species recognition and attachment has not disappeared from the human species—not in the slightest. Despite mankind having now undertaken a complete overhaul to its environmental circumstances, an overhaul of nearly breathtaking proportions, and despite humanity having reassembled nearly all its former survival and procreative needs into a more distinctively modern garb, still, for the vast majority of the human population, its primary perceptual focus continues to be directed to all the old familiar targets—food, power, politics, safety, sex. Man still gathers gregariously around what he perceives of as popular; man continues to take his foremost comfort in the presence of others. When you examine carefully the preferred behaviors of nearly every typical human being (non-autistic human beings), you will quickly realize that man has not abandoned in the slightest his intense focus on his own species, has not shed one bit the innate ability to recognize and attach to other humans. For a large percentage of the human population, these species-focused perceptions have been carried forward essentially intact, right into modern times.

Furthermore, this intense species recognition and attachment has not been without value in advancing the human cultural transformation. A key component behind both the widespread nature and the swiftness of human behavioral and environmental change is that most humans continue to be profusely imitative of their own kind. This replicative effect is ubiquitous, but is most critical during the developmental years of children, guaranteeing that each new generation will readily adopt the current circumstances of species—no matter what those circumstances might happen to be. When humans were once hunter-gatherers, their children became hunter-gatherers too. When humans began building civilizations, their children joined right in without skipping a beat. When adults spoke Latin, their children spoke Latin as well, and when adults moved on to modern Italian, their children fell right into imitative line. Just as it once held the human species together for strictly survival and procreative purposes, this trait of intense species recognition and attachment now holds humanity together while it cascades forward through an accelerating, mostly non-biological revolution.

And yet as powerful as these strong species-specific perceptions can be in keeping a species assembled, this trait is also extraordinarily conservative with respect to a species' current circumstances—no matter what those circumstances might happen to be. The evidence of this conservatism is abundant, it can be found in the static circumstances of nearly every animal species. The effect of this conservatism hits extremely close to home, for it cemented the static circumstances of the genus Homo over many millions of years. To catalyze sudden and massive behavioral change would require a crack to appear in this intense intra-species recognition and attachment, would require that a species be able to perceive beyond just survival and procreation, beyond just itself. But if we take into account the ongoing, long-lasting, extremely static circumstances of nearly every animal species—every animal species, that is, except for modern man—we would have to conclude any alternative form of perception not strongly focused upon the species itself would have to be a form of perception exceedingly rare, would have to be a form of perception that, biologically speaking, could only be described as exceptionally atypical.

If autism is, at its root, a significant inability to recognize and attach to other members of the species, as well as to their extant behaviors and conditions, then autism already carries within itself all the difficulties frequently reported for autistic individuals—that is, any of their so-called disabilities are circumstantially earned. Development in typical individuals is heavily influenced by species attachment and imitation, and therefore any corresponding development in autistic individuals is bound to be slow, frustrating and at odds with all the rest. Social adeptness in the non-autistic population is simply the natural result of the common recognitions and attachments within the species, and thus it is not at all surprising that autistic individuals, lacking these common recognitions and attachments, are viewed to exist in a world apart, are judged to be socially disconnected. In fact, the real mystery regarding autism is that it ever managed to take hold within the human population at all, given that its fundamental characteristic runs so counter to a basic support of survival and procreation. But take hold autism has; and thus it would not be unreasonable to ask of scientists that they pause for a moment and contemplate the consequence.

Without a strong species recognition and attachment to help organize their experiences and perceptions, autistic individuals, especially young autistic individuals, are faced with the daunting task of overcoming a nearly complete sensory chaos. Typical individuals organize their experiences around other people; typical individuals organize their perceptions around what other people do. But autistic individuals, significantly detached from the other members of the population, cannot organize their sensory experiences in quite the same way (with a variety of sensory difficulties naturally resulting). Fortunately for autistic individuals, and fortunately for the entire human race, the non-biological world seems to have supplied an alternative form of perceptual organization, one that has remained apparently untapped right up until around 50 thousand years ago.

It would be difficult to describe at its most fundamental level the nature of these self-organizing environmental features, or to explain what it is about them that causes them to inherently stand out. But for the purposes of this discussion it is enough to note that humans have recognized and distinguished these organizing features through the use of such names as symmetry, repetition, mapping, pattern, structure and form. From the sensory chaos that would otherwise be their fate, autistic individuals, especially young autistic individuals, focus on and organize their sensory experiences around these surrounding, mostly non-biological elements of symmetry, structure and pattern. This becomes most evident while observing the characteristic autistic behaviors, often called restricted or repetitive behaviors—lining up toys, spinning wheels, turning on and off switches, rhythmically flapping hands—behaviors abundantly steeped in pattern, behaviors profusely intent on form. Although the autistic perceptual focus will often broaden with age, even to the point of eventually incorporating species and social interests, when we examine carefully the preferred behaviors of nearly every atypical human being (autistic human beings), we will quickly realize that instead of organizing their experiences around other people and around the species itself, autistic individuals gravitate more frequently to those perceptions organized around the various structures that naturally emerge from the surrounding, non-biological world.

And it is not just in the preferred behaviors of autistic individuals that we can witness the influence of these non-biological, self-organizing concepts. Intelligence, language, memory, numeracy, artistry, technological tool-producing vision—at the core of each behavioral element on that list, at the core of each behavioral element marking the sudden human transformation, you will find a deep foundational reliance upon these very same concepts, the concepts of symmetry, repetition, mapping, pattern, structure, form. Autistic individuals, through the needful circumstances of their rather precarious biological condition, have opened a perspective onto a world that goes far beyond immediate biological need, goes far beyond the tightly gripping focus of survival and procreation alone. By bringing their unique perspective to Homo sapiens itself, autistic individuals have spawned an unprecedented biological revolution—they have jarred the human species entirely from its former animal course.

Much like Klein's mutation hypothesis, my suggestion regarding autism is a theory not easily falsifiable, not if falsifiability requires measuring the autistic presence and influence of 50 thousand years ago. For the moment, we must remain content with weighing evidence that is more indirect, such as those studies demonstrating that non-autistic children are more naturally drawn to human-derived biological images, while autistic children are more attracted to non-biological contingencies possessing pattern and form (Klin et al., 2009). But perhaps an even more compelling reason for considering autism as the likely catalyst behind man's great leap forward is to recognize that autism-inspired behavioral and environmental change continues apace all around us, even at an accelerating rate. The great leap forward did not come to an end on the East African plains, it was not just a solitary event from 50 thousand years ago. That same transforming phenomenon exists right before our very eyes, we can witness its ongoing impact nearly each and every day.

To take just one instance from many—a prominent instance—we can consider the case of Isaac Newton and his inspired laws, along with the resulting industrial, scientific revolution. Here we find a single individual—an individual known for his unusual demeanor, an individual known for being socially detached—filled suddenly with a strange new perspective upon his surrounding, mostly non-biological world, drawn deeply into the patterns and structures no human had ever perceived before. By reconstructing the form of his unique vision through the use of such tools as language and mathematics—tools which themselves are richly steeped in form and pattern, tools which themselves were greatly augmented by Newton's innovative perception—by reconstructing the form of his vision into the human environment itself, Newton made his surprising perceptions accessible to nearly all. From there, humanity's gregarious, imitative, self-preserving nature took care of the matter of dissemination, and in less than two hundred years time man's cognitive, behavioral and material world had become entirely transformed. The unusual perceptions of one atypical man, followed swiftly by an overwhelming human revolution—it is a narrative that might sound remarkably familiar.

The discovery of Newton's laws of motion, gravitation and optics were obviously not the result of a genetic mutation; the resulting industrial, scientific revolution was clearly not brought about by a universal synaptic rewiring (although I certainly would not put it past modern scientists to attempt those foolish claims). The only plausible, sufficiently pliant location for human intelligence, language, artistry and the like is within the human environment itself. Only there can the features of human revolutionary change be creatively introduced, innovatively modified, by individuals with an unusually broadened eye. Only there can these same features be imitatively multiplied, spread rapidly from place to place, by a species focused on one another, by a species focused on enhancing its self-preserving interests. In this mechanism we see the elements of both suddenness and power, we see the two essential ingredients at the heart of Klein's out-of-Africa story.

If you search the Internet you can find a web site devoted to something called the Neanderthal theory of autism—what appears to be a very loose mixture of dubious anthropology alongside vague suggestions that autism reflects distinctive Neanderthal behaviors passed along through interbred human genes. I will let the dubious anthropology speak for itself, but as for the notion there were any distinctive Neanderthal behaviors that could have been passed along in any particular way, Klein's paleontology sounds the death knell to all of that. Nowhere in the fossil or archaeological record can there be found the slightest indication that Neanderthals behaved in ways differently than those of simple primates; Neanderthals exhibited an unremarkable lifestyle that continued unabated right up to the point of their extinction. The Neanderthals were overrun by the human big bang; they were not its participants.

There is one aspect to this notion, however, that has potentially productive merit. Recent genetic analysis (Green et al. 2010; very preliminary, still subject to verification) indicates there may be a small amount of Neanderthal-derived DNA currently within the human genome, with a strong indication this likely resulted from species intermixture that occurred prior to the Homo sapiens revolution. Such intermixture would not be entirely surprising; the different Homo-based populations shared fluid geographical boundaries, and interactions between Neanderthals and Homo sapiens could have taken place on numerous occasions, with gene flow possible in either or both directions. If so, such an intermingling of genetic material could provide a conceivable mechanism for explaining the characteristics of a species non-recognition. That is, it could be surmised that beyond a certain threshold, the presence of intermixed species genes might produce in certain individuals a difficulty in recognizing and attaching to the other members of the population around them—precisely the characteristic described above as the fundamental basis of autism.

All this would be highly speculative of course, with a good deal still to be explained, and the most that could be suggested for now is that as genetic information continues to be gathered from autistic individuals, Neanderthal fossils, and the entire human species, a comparative analysis is possibly warranted. It should be noted, however, that even if it were true that moderate species intermixture provides a mechanism for a species non-recognition, that explanation would only give rise to a still larger and perhaps more difficult question since such a mechanism would not be uniquely human. Over Earth's vast history we would expect to see thousands, if not millions, of similar inter-species events; but as far as we know, it has been only in Homo sapiens that autism has taken hold. Autism's intrinsic survival and procreative disadvantages do provide some expectation that autism would only rarely gain species traction; but still, it must be answered why the outcome was entirely different some 50 thousand years ago. What was it that uniquely turned that particular moment into such a stunningly explosive event?

Through his stubborn insistence on appealing to the evidence of the archaeological and fossil record, and through his stubborn insistence in arguing for both the suddenness and the power of mankind's remarkable turn, Richard Klein has presented humanity with an exquisite challenge—the challenge of explaining the species' own shocking history. Klein's proposal for how that unprecedented transformation might have come to be—a sudden and rare genetic mutation producing significant neurological effect—it remains true to the parameters of Klein's presentation, but falls victim to the anthropocentric failings of modern science.

Klein's anthropological work has been far too extraordinary, far too clarifying, to be cast as victim; Klein's exquisite challenge deserves an equally exquisite solution. Thus it is that I suggest autism as the key to the out-of-Africa story. Autism—quirky, fragile, misunderstood, too often cruelly treated—autism represents that form of human perception not focused upon the species itself but instead upon the symmetry, pattern and structure to be found in the surrounding, non-biological world. It is that atypical form of perception that has driven humanity's atypical turn, and it is that atypical form of perception that continues to catalyze human change right through the present day.