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.?
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 D?sseldorf, 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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