SETI scientists
and astrobiologists share a common challenge: they are limited in the amount of
observational data they can gather to test their theories.
SETI researchers
are separated from potential interlocutors by the vast distances between stars.
Geologists studying other planets and moons within our solar system face a
similar challenge, exploring other worlds through the proxy of spacecraft.
Clinging
to Observations
But even
when we can go to other worlds, the amount of information we can gather is
seriously limited. The wildly successful Mars
Exploration Rovers have each covered only a few miles of terrain in over
four years of travel on Mars, amounting to a tiny fraction of the planet's
surface. Consequently, conclusions built on observations at these locations
should be extrapolated to other regions with caution.
A vivid
reminder of the limitations of such "local knowledge" comes from NASA's Phoenix
Mars Lander, now exploring the North Plains of Mars, an arctic region with
unique conditions. Early in the Phoenix mission, scientists encountered
unexpected challenges in analyzing soil samples at this polar landing site,
where soil "clumps" so readily it's difficult to get into the ovens designed to
analyze the soil's chemical composition. Based on previously available
observations, there was no hint that arctic soil on Mars would
be "clingy."
Fragmentary
Evidence
As we move
from understanding extraterrestrial geology to understanding extraterrestrial
cultures, additional challenges arise. By the nature of the instrumentation we
use to process signals during SETI observations, we may well be able to detect
distinctly artificial signals without being able to extract any
information-rich messages embedded within the signals. We could know that
extraterrestrials are out there, but have no direct way of knowing much about
them.
In a sense,
we are faced with challenges akin to those of anthropologists who reconstruct
extinct species from fragmentary evidence. Like SETI scientists,
anthropologists are looking for evidence of other forms of intelligence, and in
the best case scenario, they have only a fraction of the observational data
they would like. What lessons might
SETI scientists learn from them?
A
Half-stooping Slouch
Consider
for a moment the challenges anthropologists faced in reconstructing Homo
neanderthalis, first discovered near Düsseldorf, Germany, in 1856. By the
early twentieth century, it was widely held that these now extinct hominids
were brutish in form. For example, in 1924 G. Elliot Smith described an
"uncouth and repellant Neanderthal man" in his book The Evolution of Man:
"His short, thick-set, and coarsely built body was carried in a half-stooping
slouch upon short, powerful, and half-flexed legs of peculiarly ungraceful
form."
A few years
earlier, Henry Fairfield Osborn included illustrations of stooped Neanderthals
in various editions of his book Men of the Old Stone Age, where he said
that Neanderthals had "knees habitually bent forward without the power of
straightening the joint or of standing fully erect," and that their hands were
deficient in fine motor control, lacking "the delicate play between the thumb
and fingers characteristic of modern races."
A
Thoroughly Unattractive Fellow?
Similarly,
William Straus and A. J. E. Cave, in their 1957 article "Pathology and Posture
of Neanderthal Man," described the stereotype of Neanderthals in the
mid-twentieth century as follows:
"Neanderthal man is commonly pictured as but incompletely
erect; as an almost hunchbacked creature with head thrust forward, knees
habitually bent.... According to this view, he was a thoroughly unattractive
fellow who was but imperfectly adapted to the upright, bipedal posture and
locomotion characteristics of the modern type of man."
There's
only one problem. Anthropologists now believe Neanderthals walked upright.
The turning
point came with the article by Straus and Cave just noted. After citing all of
the same passages mentioned above that characterize Neanderthals as stooped,
they made the compelling case that this stereotype was based on excessive
emphasis on one particular Neanderthal.
A
Neanderthal who just happened to have arthritis.
Bathed,
Shaved, and Dressed in Modern Clothing
Central to
this image of Neanderthal as brutish savage was the reconstruction of one
especially complete skeleton, found in La Chapelle-aux-Saints, by French
anatomist Marcellin Boule. Why did this particular skeleton play such a
dominant role in determining our image of Neanderthals, when there were many
other remains discovered elsewhere?
The
skeletal remains from La Chapelle-aux-Saints, it turns out, included a good
sampling of vertebrae—bones essential to reconstructing a hominid's posture.
Given the interest in understanding the gait of early hominids, Boule's specimen
was a logical starting point.
And while
the Neanderthal from La Chapelle-aux-Saints may have had the stooped
posture characteristic of a modern day human with arthritis, other Neanderthals
didn't. Moreover, the La Chapelle-aux-Saints Neanderthal didn't look like the
Neanderthals in Osborn's book. Rather, Straus and Cave argued, "if he could be
reincarnated and placed in a New York subway -provided that he were bathed,
shaved, and dressed in modern clothing - it is doubtful whether he would
attract any more attention than some of its other denizens."
Compounding
the fact that this particular Neanderthal had arthritis, Straus and Cave
contended, was the widespread presupposition that Neanderthals were ancestral
to all later hominids, rather than an independent line. Consequently, it would
be natural to attribute them with more ape-like characteristics - a trap that
many anthropologists fell into.
Mirrors
of Our Assumptions
What
lessons can SETI researchers gain from the reconstruction of Neanderthal posture?
First,
whether sampling Martian soil or analyzing Neanderthal bones, the conclusions
we draw will depend on the observational data we have available. If we find a
civilization on a planet circling a sun-like star, should we expect that it
represents a typical extraterrestrial civilization?
I think
not. Rather, we should anticipate that this particular observation - this
particular civilization - is influenced by a panoply of biological, cultural,
and historical factors that we will only be able to sort out over a long time,
if ever.
Finally,
recall that early anthropologists were influenced in their reconstructions of
Neanderthals by their presupposition that Neanderthals represented a phase of
development in the evolution of Homo sapiens. So too should we be
careful to guard against imposing our own presuppositions onto extraterrestrial
civilizations, making our images of extraterrestrials not so much reflections
of their true nature, but rather mirrors of our assumptions.
Douglas A. Vakoch is Director of Interstellar Message
Composition at the SETI Institute and an Associate Professor of Clinical
Psychology, California Institute of Integral Studies.
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