[Edit 02/11/2017: The final version of this essay can be found here.]
What makes a biological species such an intriguing concept is its
stasis. From out of a near maelstrom of biological and evolutionary
dynamics—selection, genetics, generation—a species emerges as
something obstinately distinct, stable and enduring. Darwin himself
was puzzled that nature does not formulate instead into a mish-mash
of morphologies and traits, with a more gradual and more frequent
variation across space and across time. This puzzlement—an aspect
of what is often referred to as Darwin's dilemma—has never
been completely resolved. Modern explanations for nature's tendency
to coalesce into well delineated and persistent species usually
center around the notions of reproductive isolation and costs of
rarity, but in many respects these accounts miss a good deal of the
point. A species is not only static and conservative in its
morphology and reproductive viability, a species is also static and
conservative in its overall behavior, to the point of being almost
perfectly predictable across the entirety of its existence. If for
instance one were to film a documentary on almost any plant or animal
species, place it inside a vault for a hundred thousand years, one
could then remove the documentary and promote it as still accurate
and up-to-date, without the slightest need of an edit. This dogged
constancy across the entire reach of the phylogenetic network appears
to be the evidence of an underlying biological invariance—a law if
you will—a law that has not been adequately determined.
And to make the matter yet more puzzling, there is the one notable
exception to the law, the one case of the law having encountered a
blatant violator—that is, the human species.
Humanity certainly did not begin as the most obvious
counterexample to the notion of species stasis. The genus Homo
and its predecessors had for millions of years been unfolding into an
entirely standard set of stable and generally durable groupings:
afarensis, africanus, habilis, ergaster,
erectus, heidelbergensis,
neanderthalensis. And for quite some time Homo sapiens
too appeared to be slated for the same usual course, its members
passing through typical and mostly unvarying animal lives within the
more hospitable corners of the African continent. But it was around
fifty thousand years ago that an unprecedented behavioral
transformation began to take shape within the species, a
transformation that has only accelerated throughout the intervening
years and today shows no signs of abatement. In the early
twenty-first century almost no characteristic of human behavior would
be recognizable to anyone who could have observed or recorded man's
earlier days on the savanna. And although it is indeed behavior
that constitutes the most clearcut difference between the humans of
today and the humans of the past, with the advent of everything from
dental implants to artificial knees, from Viagra to augmented bosoms,
from in vitro fertilization to stem cell technologies, it is evident
that much of the morphological and reproductive intransigence still
lingering within the human species is now on the verge of
disappearing as well.
And so there are two questions to be investigated regarding the
concept of a biological species: one, what compels a species, across
all its generations, to maintain such consistent and stable behavior,
and two, how is it that the human species has managed to escape this
compulsion?
To better understand the behavior of a species, perhaps the best
place to begin is with Immanuel Kant. Kant was the first to fully
confront the challenge of describing how a behaviorally productive
biological consciousness can arise from the continuous multitude of
sensory impressions that each organism receives, impressions that in
their rawest form would be little more than chaotic and overwhelming,
would be little more than useless noise. Kant's approach, including
its heavy reliance upon syllogistic logic, was perhaps not entirely
adequate to the task (C.S. Peirce would later improve the framework
greatly). Nonetheless, Kant's groundbreaking effort still manages to
capture the essence of what would have to be incorporated into any
proposed solution to the problem, namely a recognition that in order
for biological consciousness to exist at all, an organism's multitude
of sensory impressions would have to be unified under some
kind of structure or rule. Or to put it in the parlance of modern
data science, each organism's raw sensory input would have to be
sorted, filtered, mapped and reduced, resulting finally in the kind
of perceptual foregrounding and targeted awareness that could serve
as the basis for productive behavior. Kant's depiction is too often
taken to be merely philosophical or as applicable to human reasoning
alone, but in fact it is most informative when applied biologically:
the early pages of the Critique of Pure Reason outline a
general framework whereby a manifold of biological stimulus can be
transformed into a precise and targeted response, something no lion
on the prowl could ever do without.
Kant was also the first to recognize that the means of any
sorting, filtering, mapping and reducing would have to be provided (a
priori) by the organism itself, and that the general form
of these means would be the primary determinant of the organism's
perceptual content (and therefore the primary determinant of the
organism's resulting behavior). Kant often used the somewhat vague
and magical-sounding term faculty to delineate these
organism-provided means, but of course it has to be remembered that
Kant was writing well before the advent of Darwin, Mendel and an
accurate rendition of Earth's biological timeline, so some vagueness
and magic are to be excused. Today, post the advent of Darwin, Mendel
and an accurate rendition of Earth's biological timeline, the a
priori means that underlie sensory unification and perceptual
grounding are now richly detailed and more deeply understood, having
shed their vagueness upon a wealth of observable information
regarding biochemistry and genetics, and having cast off their
magical aura behind a well described evolutionary process that has
spanned hundreds of millions of years. In the biological kingdom,
what drives the means for sorting, filtering, mapping and reducing,
what shapes the structure and rule behind stimulus unification and
targeted response, are the ongoing requirements of survival and
procreation—physically manifested within each organism's
biochemical structure and honed into effectiveness through enormously
long stretches of selection and generation.
The capstone of Kant's description, his list of conceptual
categories—organized under such headings and subheadings as
quality, quantity, modality, plurality, negation—was arrived at in
an attempt to achieve maximum generality. But in a certain sense all
this ardent abstraction overshoots the mark when applied in a
biological context, where really only concreteness will do. If one
were to search from the treetops of the Amazonian rain forests all
the way to the depths of the ocean floor, it would be a frustrating
endeavor to find anywhere a biological consciousness unified around
such notions as quality, quantity, modality, plurality, negation. And
yet it would be little more than child's play to find a biological
consciousness unified around such notions as food, water, danger,
shelter, family, sex, predators, prey, conspecifics. It is biological
need that determines the primary structure of biological perception,
and it is the pervasive and unyielding impulse behind these
biologically driven categories that provides the first indication of
why biological behavior remains so consistent and stable. Survival
ceaselessly asserts its decrees, procreation fervently presses its
demands, evolution ruthlessly carries out its mandate, and each
organism, both outwardly and inwardly, must adhere to these strict
regulations or else disappear. And so in broad and inexorable
lockstep, the members of the biological community aim their rapt
attention towards food, water, danger, shelter, family, sex,
predators, prey, conspecifics—and then respond accordingly, and
respond mostly the same.
Of the biologically driven categories, conspecific awareness and
recognition holds special significance: it is the primary catalyst—at
least within the animal kingdom—behind each species developing a
strong tendency to coalesce, both territorially and behaviorally.
Each organism appears to possess a predisposition to foreground first
and foremost those sensory impressions that are directly associated
with the other members of its species—lions perceive and attend
primarily to other lions, geese perceive and attend predominantly to
other geese, ants perceive and attend chiefly to other ants (and of
course humans perceive and attend first and foremost to other
humans). The principal inducement towards this nearly universal
characteristic is that it is the most direct solution to an otherwise
haphazard reproductive challenge. Successful mating requires that
male and female conjoin at the same time and at the same location, a
rendezvous that would be made problematic, if not downright
impossible, should each member of the species be unable to
distinguish and foreground its own kind from all the remainder—a
perceptual blindness that would be practically guaranteed without
inherent conspecific awareness, since there is nothing within sensory
impressions by themselves that would help promote one class of
perceptions over another. Even in those rare cases where organisms
live solitary lives and egg-laying and fertilization are separated in
time, the species is still bound together by the perceptual
foregrounding of the expected location of egg-laying and
fertilization, in this instance an effective proxy for conspecific
prominence.
And beyond the logistical requirements of procreation itself, many
species make heavy use of conspecific foregrounding to advance a
broad range of beneficial behaviors. Nurturing of the young for
instance necessitates that adults carry a perceptual preference for
the offspring of their own kind—lest lions find themselves randomly
rearing goslings, geese find themselves indiscriminately raising
ants, and so on. Successful foraging, pack hunting and herd defense
all depend upon a keen perceptual attention to the other members of
the population, even when those members occupy no more than a
minuscule portion of the entire sensory field. But perhaps most
importantly of all, conspecific awareness and recognition allows
tried-and-tested species behaviors to be passed along from generation
to generation without the inefficient obligation that each and every
behavior be imprinted genetically or made completely instinctual. The
maturing members of many species go through a period of time in which
their main occupation is to scrutinize parents, siblings, extended
family and other models within the population, imitating observed
activities and eventually taking on those activities with an
increasing faithfulness (and thereby becoming models for the next
generation). This recurrent cycle of learned and transmitted behavior
is always confined to the species itself—lions do not learn from
leopards, geese do not model sparrows, no organism imitates
non-biological objects. Each organism is a fully engaged student of
its own kind—and is nearly oblivious to everything else.
Thus the trait of conspecific awareness and recognition has both
the powerful and the restrictive impact of making a species insular.
Conspecific foregrounding encourages the species to cluster, it turns
the species' members inwards for mutual protection and predatory
assistance, and it promotes generational continuance of the species'
more successful behaviors. But the unrelenting narrowness of this
characteristic also has the consequence of effectively blinding the
species to any alternative information the sensory field might have
to offer—whether that information would come from other species or
from the non-biological world. Nearly all sensory impressions not
directly connected to the species itself or to the immediate
requirements of survival and procreation are relegated to the sensory
background and never gain perceptual prominence, and thus never
influence biological attention or behavior. As a result, the species
is provided little opportunity for change, since perceptually
speaking nothing ever differs from generation to generation. So
powerful and so confining is the impact of conspecific awareness and
recognition that it really needs to be considered an essential part
of the definition of a species, for a species is determined
not only by its morphological similarities and its reproductive
sufficiency, it is also determined by the mutual awareness and
recognition of all its members, the glue that holds the species
together and assures its unvarying continuance.
The inherent perceptual inclination towards conspecifics, along
with the corresponding disinclination towards other species, suggests
there is a boundary between these two extremes. On one side of the
boundary, conspecific awareness and recognition must function within
a certain range of tolerance, for despite there being varying levels
of genetic and morphological difference among species members,
conspecific foregrounding remains active and strong in nearly all
population circumstances. But this tolerance clearly has its limits,
because it does not extend so far as to include the other species,
and thus it can be assumed that as conspecific distance increases
between organisms (a function most likely of increased morphological
and/or genetic difference), a boundary is eventually reached where
the tolerance is fully extended and then finally exceeded, with a
corresponding attenuation and loss of conspecific awareness and
recognition.
These concepts of conspecific distance, tolerance and boundary
play an important role in assessing the expected outcome and impact
of an organism that introduces genetic alterations into a species. A
new genetic signature carrying differences that are only minor in
effect and/or infrequent in number will likely leave the bearer
within the conspecific tolerance range, meaning that the bearer will
experience typical conspecific foregrounding and typical conspecific
perceptions and behaviors, improving the chance for continuation of
these minor mutations. This must happen to some extent with nearly
all offspring, because each organism possesses a genetic signature
that is unique to some degree, and yet in the large majority of cases
this uniqueness does not interfere with conspecific awareness. By
contrast, a newly introduced genetic signature that carries
differences that are major in effect and/or frequent in number
increases the likelihood that the conspecific distance between the
bearer and the other members of the species will become so large as
to strain or even surpass the conspecific tolerance range, thereby
weakening or even nullifying conspecific awareness and recognition.
To take an extreme example, one might imagine a lion being born with
such an exaggerated level of genetic mutation that it is effectively
a leopard, meaning that this newborn and its “conspecific”
neighbors are destined to become perceptual strangers, with survival
and procreative consequences almost certain to turn negative. Even at
much lesser extremes of conspecific distance, challenging biological
consequences can still be anticipated, and thus conspecific
distancing almost certainly plays a role in the thwarting of
significant genetic change within a species, another manner in which
conspecific awareness and recognition contributes to the ongoing
stasis of a species.
Although the odds of continuation are indeed negligible for an
organism outside the conspecific tolerance range, the prognosis is
more uncertain, and in some ways more intriguing, for an organism
approaching the boundary—near enough that conspecific awareness and
recognition is weakened to some degree but not so near as to make
survival and procreation essentially impossible. There are several
distinguishing characteristics that can be predicted for such an
organism. Mating for instance, although not precluded, will certainly
be more problematic, since the organism's inherent perception for
potential mates, as well as their perception in turn for it, will be
more hazy than is the case for the rest of the species, leading to
coupling behaviors that might seem distant or strange. In species
that make heavy use of conspecific foregrounding for mutual defense
or combined attack, an organism stretching conspecific tolerance will
of necessity be a weaker participant in these group activities and
might come to be regarded as an encumbrance by way of result. And
perhaps most importantly of all, the maturation process for a
conspecifically distanced organism will almost certainly be more
difficult and more delayed than for its peers, its relative inability
and disinclination to scrutinize others in the population and to
imitate their behaviors hampering the typical transmission of species
behaviors. Such an organism will not only physically be an
outsider to the population, it will also perceptually and
behaviorally be an outsider as well.
On the other hand, the challenges faced by an organism near the
conspecific border do provide the potential for an ironic
compensation. It needs to be remembered that the primary purpose
behind an inherent form of biological perception is to unify sensory
impressions, impressions that would otherwise remain chaotic,
overwhelming and useless. And to the extent that an organism's
perceptual mechanisms are diminished by its biological circumstances,
the corresponding unification of sensory experience will be
diminished as well. Such weakening of sensory unification will likely
give rise to an assortment of sensory difficulties—hypersensitivity,
hyposensitivity, synaesthesia. In order to ameliorate these
difficulties, a conspecifically distanced organism, detached in
significant degree from one of its primary means of sensory
unification, will be driven towards alternative means of
sensory unification—which is to say, it will be driven towards
alternative means of perception. This effectively opens the door to a
wider awareness of alternative features within the sensory field,
such as those provided by the other species, and more significantly,
those provided by the non-biological world. It is well known that the
non-biological world provides a rich framework of organizing
principles that can serve as the basis for unification of sensory
experience, principles that go under such names as symmetry,
repetition, pattern, structure and form. These organizing principles
are in theory available to all organisms, but the restrictive effect
of biological perception in general, and conspecific awareness and
recognition in particular, usually pushes awareness of these
non-biological features well into the sensory background. And thus
ironically, it is only the organisms that get loosened from
the strictures of conspecific awareness and recognition that gain the
opportunity to foreground these alternative features from the
surrounding environment, and thereby gain the perceptual freedom to
achieve a broader and deeper awareness of the entire sensory field.
If there were only one such conspecifically distanced organism or
even a few such organisms extant within a population, there would
likely be little impact on the species as a whole. But if the
population were to possess a significant number of such organisms,
and that number were to remain stable for a reasonable period of
time, the species dynamic could begin to change. All the necessary
conditions for a change would be in place: the broader population
would have a conspecific relationship to the population's more
distant members (albeit a looser relationship than normal), and the
more distant members would have access to a wider array of perceptual
experience. The natural workings of conspecific awareness and
recognition would prompt the broader population to begin to notice
the new behaviors and new perceptions being originated by the more
distant members, an awareness that might even encourage imitation. In
this manner the enhanced perceptual experience of the population's
more distant members would begin to infiltrate the perceptual
experience of the species as a whole, and with a change in species
perception would come a corresponding change in species behavior. In
defiance of the universal expectation of a continual species stasis,
this species would be on the verge of a behavioral revolution.
Of course considering the biological fragility that haunts the
conspecific boundary, and observing the non-changing behavior of all
the species to be found in the natural world, it would seem that any
talk of behavioral revolutions being driven by conspecific distancing
would have to qualify as little more than academic exercise, some
hypothetical musing. And indeed that would be the end of the matter,
if it were not for the one piece of unfinished biological
business—namely the one species that has emerged suddenly and
prominently as a blatant violator of the tenets of species stasis,
the same one species (not coincidentally) that has broadly expanded
its perceptual experience of the sensory world, the same one species
(not coincidentally) of which it can no longer be said that it is to
be found in the natural world. The human species.
The behavioral revolution of the human species has been nothing
short of stunning in both its scope and its speed. There is little in
the way of hard evidence to suggest that prior to around fifty
thousand years ago Homo sapiens individuals lived much
differently than all the other animals—riding the ebbs and flows of
survival and procreation, gazing out upon an entirely natural
landscape, confined to the African continent alone. And then suddenly
everything began to change. Art, symbolism, categorized tools,
sophisticated weaponry—all began appearing in ever increasing
numbers and with ever advancing technique. Humans began to spread
geographically and did not stop until the entire planet had been
covered. They extincted many other species along the way and bred a
chosen few into a domesticated abundance. Today, very few humans gaze
out upon an entirely natural landscape—artificial environments have
become vastly the human norm.
One notable aspect of this human revolution is that has been
accompanied by—indeed it has been driven by—a broadened
perceptual awareness of the sensory world, including a much broadened
perceptual awareness of the non-biological world. Nearly all the
changes that have become the hallmark features of modern human
existence have been built upon a backbone of non-biological
constructs, everything from the grammatical patterns of language all
the way to the structured symmetries of towering skyscrapers.
Literally everywhere one looks, one finds the profuse application of
the organizing principles of pattern, symmetry, repetition, structure
and form, principles that never would have reached the surface of
human ken not that long ago, but today constitute the proliferating
and artificial embodiment of man's ever burgeoning intelligence.
Thus the characteristics of the human behavioral revolution can be
seen as matching the description given above for a species change
brought about by the influence of conspecific distancing. The
enormous human behavioral change has been accompanied by an equally
enormous human perceptual change, by an expanded perceptual
awareness, one that goes far beyond the restrictions of biological
perception alone. Humans still have their conspecific awareness and
recognition for one another, and they still possess their sensory
instincts for survival and procreation, but humans are no longer
confined by these perceptions, the species has been freed
entirely from its former perceptual prison.
The predictions of conspecific distancing would suggest that this
liberation must have been catalyzed through the influence of a
significant and stable sub-population of conspecifically distanced
humans, relative outsiders who driven by biological and sensory
necessity would have been the first to explore a different means of
seeing the world, the species' pathfinders to expanded forms of
perception. And so the question needs to be asked: within the human
population, is there a recognizable subgroup of members who can be
seen as carrying the distinguishing characteristics (including the
challenges) of a conspecifically distanced organism and who also
possess the compensating trait of an expanded perceptual awareness,
an awareness that often shies from typical biological perception but
that gravitates more readily to alternative perceptual targets,
targets such as the non-biological world and its organizing
principles of pattern, symmetry, repetition, structure and form?
Within the human population, there is indeed such a group of
people, and over this past century they have begun to be recognized.
They are defined most accurately as autistic.
Autism has been giving the scientific community a very difficult
time. The condition was first regarded as extremely rare and almost
always debilitating, but as evidence has mounted over the years it
has become more and more clear that at least one percent of the human
population can be described as autistic, and along with such numbers
has come the inevitable corollary that in the large majority of
circumstances the condition cannot be all that debilitating. Autistic
individuals certainly face some challenges, challenges that can vary
in degree, but that has never prevented autistic individuals from
blending in with the rest of the human population, so much so that
they have gone virtually unrecognized for dozens of millennia.
Nonetheless, even in the face of these accumulating facts, the
scientific community has been unable to let go of its need to
medicalize the condition, somehow convinced, without evidence, that
autism must be the result of biological defect. And so the research
and studies have been growing like weeds, searches for defective
genes, searches for defective neural pathways, searches for defective
metabolisms—massively funded and massively peopled efforts that
have now become laughable in the combined fruitlessness of their
results. And more troubling still—and certainly more shameful—has
been the scientific community's willingness to heap insult and
torture upon its autistic subjects, branding them with an assortment
of inaccurate and unsupported labels (burdens, tragedies) and
stifling them with an assortment of damaging treatments and so-called
cures (applied behavioral analysis, stupefying drugs). The scientific
community's present approach to autism is destined to become one of
that community's more humiliating hours.
A far more accurate approach to understanding autism is to regard
it as a condition of increased conspecific distance. All the core
characteristics of autism—what nearly every autistic individual
shares in common—are the very same characteristics predicted of an
organism that is much nearer to the conspecific border than the
majority of its peers. Autistic individuals, although very much a
biological part of the human population, show less inclination for
and less attention to their conspecific neighbors, a trait which is
often taken as evidence of damaged social functioning but upon
careful observation is more precisely described as a diminished human
awareness, an attenuated human recognition. Autistic children, less
inherently prone to the activities of conspecific observation and
conspecific imitation, mature more slowly than their non-autistic
counterparts, sometimes taking well into adulthood to assume a fuller
role within the broader population. Autistic individuals experience
an assortment of sensory anomalies—hypersensitivity,
hyposensitivity, synaesthesia—conditions that seem to have no
discernible physical cause and no tangible consistency from
individual to individual, evidence that these anomalies stem not from
physical defects but instead from a more generalized difficulty with
the attainment of sensory unification. Finally, and almost
invariably, autistic individuals compensate for their diminished
conspecific awareness and recognition by concentrating instead on
alternative perceptual targets, including a predominance of targets
from the non-biological world. In the youngest autistic individuals
this is most often seen in the rapt attention given to such things as
spinning objects, symmetrical figures, repeated sounds and scenes,
and in older autistic individuals this characteristic often coalesces
into specialized and deeply learned interests. Sadly, the term
repetitive and restricted behaviors is often used to
disparage these concentrations on alternative perceptual targets,
betraying a complete misunderstanding of both their necessary purpose
and their liberating consequence. For these concentrations on
alternative perceptual targets are both the creative antidotes to
what might otherwise be an overwhelming sensory chaos, and they are
also the opening doors to the organizing and intelligence-producing
principles of pattern, symmetry, repetition, structure and form.
The key role that autistic individuals must have played—and are
continuing to play—in the sparking of the human behavioral
revolution can be seen in the oddly consistent feature that has
emerged at each point of human perceptual and behavioral change.
These changes are always launched by individuals and their
discoveries (never by groups), individuals who are inevitably in
possession of a distinguishing and uncommon set of traits. From
Socrates to Newton to Beethoven to Einstein—and at each
transforming moment of genius in between—the human revolution has
been powered by individuals who seem to be mostly detached from the
typical concerns of society and species, and who are instead
obsessively focused on alternative concerns, often non-biological
concerns, concerns that the rest of the population might describe as
worthless or strange. It has never been much of a secret that the
personal characteristics of genius tend to be rather odd; all that is
being noted here is that these personal characteristics tend to be
odd in a predictable and recognizable way. One might call these
individuals of genius autistic, or one might call them
conspecifically distant—there really is no difference—but the
true mark of their genius is that they see the world not as it is and
as others perceive it, the true mark of their genius is that they see
the world exactly not as it is and exactly not as
others have already perceived it, the same compensatory and
distinguishing characteristic of a conspecifically distanced
organism, of an autistic individual.
Any explanation of the human behavioral revolution would need to
be an explanation of coincident events, because it was at the exact
same moment in Earth's enormous biological/evolutionary timescale
that humans quite suddenly underwent an entire host of unprecedented
transformations:
- They began perceiving aspects of their sensory world that
went far beyond the elements of survival and procreation alone.
- They began behaving less and less like the animals they had
formerly been, and more and more like the modern humans they were
about to become.
- They began constructing artifacts out of the material
structure of the non-biological world.
- They began displaying the tangible signs of what would become
an ever increasing intelligence.
- They began expanding geographically, conquering climates and
other species, and did not stop until they had blanketed the entire
planet.
The common explanation for the human revolution, that it is simply
a by-product of normal biology and normal evolution, fails to tie
together any of these multi-faceted events and fails to address their
suddenness and simultaneity. The notion of conspecific distancing,
however, has the merit of encompassing nearly all these different
aspects of the human revolution: it provides a direct and observable
source for the expansion of human perception; it contrasts that new
perception with biological perception, providing an explanation for
humanity's departure from animal behavior; it clarifies mankind's
sudden interest and skill with the elements of the non-biological
world; and it describes humanity's ever increasing intelligence as
the embodied reliance upon the organizing principles of pattern,
symmetry, repetition, structure and form.
Furthermore, conspecific distancing associates directly to yet
another event coincident with the human revolution. Concurrent with
the other changes taking place within the species, Homo sapiens
was undergoing a significant introgression of genetic material from
Neanderthals and perhaps other human sub-species, an introgression
sizable and pervasive enough that nearly all non-African humans
living today possess around a 2 to 3 percent admixture of non Homo
sapiens genetic material (Green et al., 2010).
There is still much to be learned about the nature and impact of this
introgressive event, but it is clear such an occurrence would be
exactly the kind of genetic jolt that could loosen the conspecific
bonds of a species and potentially give rise to many generations of
conspecifically distanced individuals.
All these simultaneous and fast occurring events, along with the
nature of the autistic population living today, serve as the strong
circumstantial evidence that the human behavioral revolution was not
an event of normal biology and normal evolution, but instead was an
event driven by the characteristics of conspecific distancing,
characteristics that ultimately gave rise to an evolution-shattering
and universe-unveiling aberration—the lone counterexample to the
law of species stasis.
References
Green, R.E.,
et al. (2010). A draft sequence of the
Neandertal genome.
Science 328, 710–722.