Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization

First Edition

© 1975-1979, 2008 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm


Preface and Acknowledgements for the First Edition



The Field of Xenology

What, exactly, is “xenology”? As described by the subtitle of this book, xenology may be defined as the scientific study of all aspects of extraterrestrial life, intelligence, and civilization. Similarly, xenobiology refers to the study of the biology of extraterrestrial lifeforms not native to Earth, xenopsychology refers to the higher mental processes of such lifeforms if they are intelligent, xenotechnology refers to the technologies they might possess, and so forth.

I was among the first to attempt to popularize the “xeno-“ prefix in association with the general study of extraterrestrial life (e.g., see my letter to Nature, below). However, credit for coining the xeno-based terminology in this usage is generally given to the renowned science fiction author Robert A. Heinlein (starting in The Star Beast, Scribner, New York, 1954 HTML commentary), though the first use of the related word "xenologist" is apparently attributable to L. Sprague de Camp ("The Animal-Cracker Plot," Astounding Science Fiction 69(July 1949); "The Hand of Zei," 1950).

The scientific usage of the xeno- terminology was subsequently defended in the mainstream scientific literature by Heinlein and Harold A. Wooster in a 1961 article published in the journal Science (R.A. Heinlein, H. Wooster, "Xenobiology," Science 134(21 July 1961):223-225 PDF) and subsequently by myself in a 1983 article published in the journal Nature (R.A. Freitas Jr. (CV), "Naming extraterrestrial life," Nature 301(13 January 1983):106 HTML HTML). (Heinlein had confirmed to me, by personal correspondence in August 1980, that he still regarded his coinage as both valuable and correct.)

My article in Nature drew a complaint ("Xenology disputed," Nature 302(10 March 1983):102) from four specialist researchers claiming to represent "20 research groups in at least eight countries" who preferred to retain use of "xenology" for the study of xenon concentrations in meteorites (an argument that would not apply to other uses of the xeno- prefix) but their plea has largely failed. By December 2008, Google listed 20,600 entries for "xenology" of which only 1140 referred to xenon and most of the rest referred to the extraterrestrial usage. Online dictionaries (e.g., Webster's New Millennium Dictionary of English, 2003-2008) now typically define "xenology" as "the scientific study of extraterrestrials, esp. their biology." So far, the mainstream field seems to have settled on the name “astrobiology” (the biology of stars?), but I still harbor hope that the more etymologically correct name, xenology, can be applied to the more general field of study that I tried to help define, so long ago, with my book – titled Xenology (~500,000 words, ~150 illustrations, 4000+ references), First Edition.


Why Publish the First Edition?

Reading again the text that I first wrote 30 years ago, it feels as though this book has fallen through a time warp or a crack in time, or has just been removed from a time capsule. But while some of the material seems dated, much of it still appears fresh and new, and the synthesis of the field (of xenology) is still relevant and unique. The main purpose of this book was to help create a coherent new field of study called “xenology”.

As you read this book, please bear in mind that it was written before Sagan’s “Cosmos” TV series and predated the internet, the personal computer, the cell phone, most of genetic engineering, Ronald Reagan, all but the first few Space Shuttle launches, electronic word processors and spell checkers, and Google and online reference sourcing. It was written before the sulfur volcanoes of Io or the liquid seas of Titan had been discovered, before extrasolar planets had been observed, and before my own optical and radio telescope SETI searches and other writings on replicating systems and nanotechnology (and several years before nanotechnology had even been invented, via the 1981 PNAS paper and 1986 book Engines of Creation by K. Eric Drexler). Xenology predates the first engineering study of self-replicating systems by NASA in 1980, almost all of the important work on interstellar probe SETI, and the development of the entire field of molecular nanotechnology and medical nanorobotics. In the fictional sphere, Xenology also predates all the Star Trek and all but one of the Star Wars movies, and its writing began just 6 years after the theatrical release of the classic 2001: A Space Odyssey.

If this book is so ancient, why bother to publish it now? There are several reasons.

First, I have an emotional attachment to it, having spent so many years (5) of my life writing it, back in the late 1970s. Indeed, I wrote it during my time in law school, a very trying experience for someone accustomed to scientific thought processes. Writing this book helped keep me sane during those years. (The whole thing was typed on my trusty blue IBM Selectric typewriter, and the graphics were hand-drawn or paste-ups, which explains in part why it has taken so long to get this up into "print".)

Second, Xenology was my first major effort at bookwriting. It taught me how to research, organize and write a reasonably coherent and lengthy single-topic work. It was excellent training and taught me valuable lessons in scientific writing that I’ve put to good use in my subsequent work. Anyone who is familiar with my later work will recognize the early manifestations of my characteristic proclivity to organize information in a comprehensive, almost encyclopedic manner, imposing some coherence on the information to help create a foundation for a more rigorous discipline someday to come.

Third, the work contains many thousands of literature references – a style of writing that has also become my trademark. Please bear in mind that back in the late 1970s, all of these references had to be assembled “the hard way”. In those antediluvian days, you had to look things up in a hardbound citation index and then walk the stairs and aisles of a real bricks-and-mortar library to find the right shelf containing the exact volume that you needed, then photocopy the papers for a nickel a page. Xenology was completed more than 20 years before the advent of the World Wide Web made online literature searches and pdf document retrievals a snap.

Fourth, while this book is not as technically rigorous as my later books, there is enough good material here that I thought it deserved to see the light of day. It is also reasonably well written, and contains some unique and valuable insights that I’ve not seen published elsewhere in the last 30 years. So I think it still has a valuable contribution to make to the field.

Fifth, as far as I know there is still no single text that attempts to integrate the entire field, as Xenology does. The only book that comes close is Intelligent Life in the Universe by I.S. Shklovskii and Carl Sagan, but that was published in 1966.


History of the Book

I first got interested in the study of possible extraterrestrial life through the works of Carl Sagan in the science area and Larry Niven in the science fiction area, in the early 1970s. Also, my favorite physics professor at Harvey Mudd College, Thomas Helliwell, indulged my budding freshman curiosity about rotating black holes, tachyons, calculations on the gravitational stability of toroidal planets and the dynamical stability of ringworlds around stars. At HMC, freshman were required to conduct a full-time 1-month engineering project. For my project, I chaired a 7-man team to create a design for a fusion-powered manned interstellar spaceship ("Project MISEV").

I began accumulating materials for Xenology in 1974, and began the actual writing in 1975, finally completing the last chapter, Chapter 26, in early 1979. There were 27 chapters originally planned. I never got around to writing the introductory (Chapter 1) or concluding (Chapter 27) chapters, nor one other chapter in the middle (Chapter 9) that was intended to be a summary of the unmanned interplanetary spacecraft that had been sent to other planets as part of the actual “experimental” search for life in our solar system, with a particular focus on the Viking landers on Mars that conducted the first biochemical searches for life on another planet via direct sampling. The book contains some pretty speculative material in a few places, including material from speculative fact and science fiction writers when appropriate. But generally the text tries to stick to concepts and arguments that are grounded in some kind of precedent either in biology, technology, or the social sciences and the arts.

Xenology was privately circulated while it was being written in the late 1970s. The book was reviewed by 40 notable scientists (see below), who were first contacted by letter, then mailed one or more chapters, after which these reviewers generously offered constructive comments leading to revisions. I then attempted to find a mainstream publisher, but collected only rejection slips. Finally, a science fiction writer friend (James Hogan) recommended his book agent, Ashley Grayson, who, upon reading the entire manuscript, became very enthusiastic about its prospects. Ashley kindly spent a couple of years shopping it around to the general run of speculative science and science fiction publishers. We got a few nibbles, but in the end all the editors and publishers who reviewed it concluded that the book was too lengthy (hence necessarily would have to be too highly-priced per copy) to be a commercial success. The book continued to be privately circulated to a select few others, most notably some science fiction writers and editors of my agent’s acquaintance, throughout the 1980s. The full book was never published in print (hardcopy) form or offered for sale commercially.

During the late 1970s and early 1980s, I carved out about a dozen “science fact” articles from the book materials, which were published in Analog magazine and a number of other venues. Around this same time I became one of the principal advocates for interstellar communication via material probes rather than radio waves and published a number of technical papers on this subject. I also conducted the first SETI searches for possible orbiting alien artifacts in Earth-Moon orbits using optical telescopes, published the first engineering scaling study of a self-replicating interstellar probe, performed the first radio SETI search at the tritium hyperfine line (which, if detected, would have been unambiguously artificial), and participated in the first engineering design of a self-replicating lunar factory for NASA. These activities thoroughly distracted me from further pursuing publication of Xenology in book form.

By 1994, I’d begun my current career in nanotechnology, starting the research that would eventually lead to my first published book in the field, the first volume in the Nanomedicine series, and beyond. At a nanotechnology conference in May 1998 I met Robert Bradbury, who had a company doing life extension research but was also writing in the area of SETI and astroengineering topics. Bradbury expressed interest in my unpublished book, and after reading some of it, offered to scan it and place it online alongside his existing collection of SETI-related works. From mid-1999 to mid-2000, I xeroxed Xenology and snailmailed it to him, chapter by chapter, which he scanned in and formatted. He also paid a Russian colleague to manually type the first 4300+ references (about half of my accumulation, but including most of the references used in the book) since these were all handwritten in a notebook.

Because of the imperfect nature of the scanning process, a large number of typos crept into the text that had to be caught and manually corrected. Bradbury did a lot of this but could not catch everything. This was a job only the author could do. Also, the last two chapters included a lot of handwritten insertions into the typed text that could not be scanned, so this material (the two longest chapters in the book) was unusually heavily laden with typos, dropped sentences, missing fragments, and the like. My personal attention was required, but by this point I was employed full time as a nanotechnology Research Scientist at Zyvex, so I couldn’t spare any cycles for the necessary corrections – and again, progress on the book languished.

While I could not consent to Bradbury placing the uncorrected manuscript online for general access in its initial unedited rough form, I also could not find time to correct it. As a compromise, I agreed that individuals upon special request could view the materials, which were placed online at Bradbury’s private Aeiveos Corp. website. This at least afforded Bradbury and a few selected SETI researchers ready access to the materials during 2000-2008 on an invitation-only basis.

During the 2000s the number of requests for access to the manuscript continued to grow. So for the last few years I’ve been slowly working, in spare moments, to clean up the text, reformat the material to be consistent with my other online books, then put the book up for free public access at my own xenology.info website that I reserved in 2002 for just this purpose. I’ve largely resisted the urge to change much, making just minor editorial corrections where appropriate, adding Section numbers, renumbering Figures and Tables, and correcting typos, but generally avoiding bringing the book up to date which should be the job of the Second Edition (if one is ever written). Such updating and correction is desperately needed, but must await a proper thoroughgoing editorial process that will be undertaken (most likely) by others.

The First Edition was originally written in the style of Scientific American (e.g., pitched to a scientific layperson reader), and it maintains this non-academic style throughout. There are only a few mathematical equations in this book. The work is heavily referenced to the primary nontechnical literature on extraterrestrial life (and related material), and is well referenced to the primary technical literature in many specialized areas but not uniformly throughout.

Xenology was current as of 1979, but the field has made 30 years of progress since then. The reader will find numerous omissions of facts and valuable references that have been published in the intervening years, and probably even a fair number of outright errors which were unknown at the time of writing. I’ve resisted the urge to rework problems and present new views. Missing also are my own three SETI studies and a couple of dozen papers I wrote in the 1980s. Many concepts that are widely discussed today were relatively unknown back then; many others have found their way into science fiction during the intervening years. For the most part, the material has held up reasonably well. The first contact protocols, scenarios and taxonomy in Chapter 25 are still relevant today – and perhaps even more so, since they obviously also apply to artificial intelligences which are now much closer to fruition than they were thirty years ago. The governance scales in Chapter 21 can be used to generate thousands of different possible governmental forms; the study of interstellar governance complexity and stability has been only lightly studied academically to this day. My discussion of coboglobin-based blood (original to me) in Section 10.4 has not been replicated elsewhere. And so forth.

Most significantly, the First Edition of Xenology was written entirely in the “pre-nanotechnology” era, thus largely ignores this all-important coming development. Even so, I anticipated this field in a small way in Section 16.4.1 when I wrote: “If alien electronic artificial intellect is possible, how physically small might it be? The theoretical lower limit of cell size is about 400 Angstrom, a bit smaller than the tiniest known living organism (the PPLO). A brain with 1010 neurons of this size would neatly fill a minute cube one-tenth millimeter on a side. But artificially designed alien microbrains theoretically could be vastly smaller still. Using molecular electronics with components on the order of 10 Angstrom in size, 1010 microneurons could be packed into a space of a few microns. This is small enough to hide inside a bacterium, a fact which may have several very interesting consequences.” It remained for other authors (including myself, in later decades) to more fully explore those "interesting consequences".



I wish to sincerely thank the aforementioned Robert J. Bradbury for his constant encouragement and enthusiasm about this book, and for laboriously scanning my typewritten pages and converting them to an initial html form over a period of about 12 months during 1999-2000. Robert also painstakingly coded into html format all of the Tables and Figures, some of them very lengthy and very complex, by hand. Without Robert’s truly Herculean initial efforts on my behalf, I could not have found the personal time or energy to carry these materials across the finish line to completion. I also thank Robert for scanning in the images for numerous figures. Some of these images have poor legibility, but this is my fault, not Robert’s. These images were scanned from my copies of library originals some of which were in turn reproduced using an ancient wet xerographic process, causing them to become heavily grayed out with time. I also regret that the text is not more heavily linked. However, each paragraph and illustration in the book is tagged with an anchor point to facilitate direct URL citation.

Please note that the official version of the book, as corrected, restored, and formatted by the author, is now formally published at the http://www.xenology.info website. No other version should be cited as authoritative or regarded as authentic.

I also wish to belatedly thank my original reviewers who read parts of the manuscript and provided critical comments. This includes: R. McNeill Alexander, Norman J. Berrill, David C. Black, Jonathan Boswell, Ronald N. Bracewell, A.G.W. Cameron, J. Desmond Clark, Mary Connors, John D. Currey, Karl W. Deutsch, Stephen H. Dole, Frank D. Drake, Freeman J. Dyson, John F. Eisenberg, Francis R. Flaim, Robert L. Forward, Sidney W. Fox, Arthur Harkins, Thomas M. Helliwell, Sol Kramer, Paul Kurtz, Paul D. MacLean, Magoroh Maruyama, Stanley L. Miller, Marvin Minsky, Peter M. Molton, Barney M. Oliver, Leslie E. Orgel, George C. Pimentel, Cyril Ponnamperuma, William K. Purves, Tim Quilici, S. Ichtiaque Rasool, Jack D. Salmon, Charles L. Seeger, Mark Stull, Jill Tarter, Francisco Valdes, Gerard de Vaucouleurs, David H. White, and Edward O. Wilson. Most of their comments were integrated into the text but a few corrective items might have been missed. As a result I must apologize in advance for any errors in the original work that may have survived. All such errors should be attributed, and reported by email, solely to the author. I also thank Ashley Grayson for his efforts on my behalf.

Finally, I must thank my wife, Nancy Ann Freitas, for her patience and support during the writing of this book, more than three decades ago near the start of our married life together. Without her help and faith in me, this book simply could not have been written.

Robert A. Freitas Jr. (CV)
Senior Research Fellow
Institute for Molecular Manufacturing
6 December 2008


Last updated on 22 October 2009