Linda Billings states bluntly that Ben McGee’s “call for proactive xenoarchaeological guidelines” is not “a productive contribution to the scientific search for evidence of extraterrestrial life or efforts to communicate clearly about it.” Much of her criticism is of terminological imprecision.

I agree with her about the way the term “astrobiology” is used by McGee: at different times referring broadly to extraterrestrial life, and narrowly to intelligent extraterrestrial life.

On the other hand, her apparent dismissal of the term “xenoarchaeology” for not appearing in dictionaries fails for several reasons:

  • McGee had himself defined the term in his initial paper;
  • such a prescriptive approach would stymie neologisms of all kinds;
  • the use of the prefix xeno- to refer to extraterrestrial specialisations is uncontroversial – Billings would surely be aware of the term xenobiology, a less common synonym for astro- and exo- biology.

Section two of Billings’ paper is also problematic: she writes that McGee assumes extraterrestrial visitation in the Solar System, when in fact McGee specified “suspected artifacts”.

The use of archaeological methods to examine claimed extraterrestrial sites, what I’ve called “skeptical xenoarchaeology”, has already occurred. Such work need not indicate a preconception about the existence of extraterrestrials, and supports McGee’s prediction that future claims will be made of the discovery of extraterrestrial artefacts.

I agree that it would have been more accurate to describe such artefacts in terms of ETI rather than ‘astrobiological activity’ but I don’t think it’s indicative of equivocation.

Billings claims that xenoarchaeology is not discussed at meetings of the astrobiology community. She points to the following examples of reputable astrobiology meetings in which xenoarchaeology has not been discussed, yet her examples contradict her point:

  • the 2007 Bioastronomy conference in Puerto Rico: in which Richard Carrigan presented on his search for Dyson Spheres, and Doug Vakoch described the methodologies of archaeologists as analogous to making contact with temporally distant civilizations.
  • 2008 Astrobiology Science Conference in Santa Clara, CA: in which Eric Korpela and Andrew Howard discussed the search for extraterrestrial artefacts as a future SETI strategy.
  • Astrobiology Science Conference 2010: in which Paul Davies argued “we should search for any indicators of extraterrestrial intelligence, using the full panoply of scientific instrumentation, including physical traces of very ancient extraterrestrial projects in or near the solar system”

Billings seems to interpret McGee’s paper as an attempt to demarcate and legitimize a new, non-scientific and blurry-boundaried field of study – xenoarchaeology – by riding on the coat tails of an established and thus legitimate one – astrobiology. Of course her point could be expressed as simply an attempt to legitimise astrobiology by demarcating it from one perceived as less legitimate. Maybe her interpretation comes from McGee’s confusing use of the term astrobiology.

I’ll note in passing here Billings’ claim that “Outside the scientific community, astrobiology is virtually a household word.” It would be nice to think that, but this 2009 study found that 75% of University of Florida science undergraduates were unfamiliar with astrobiological concepts.

The following are presented by Billings as evidence of astrobiology’s legitimacy:

Government agencies ranging from NASA in the USA to the European Space Agency and Spain’s Center for Astrobiology are funding research, accredited universities worldwide have adopted astrobiology curricula (though none yet offersa PhD in astrobiology), and the journals Astrobiology and the International Journal of Astrobiology publish peer-reviewed papers on astrobiology, as do Nature, Science, and many other peer-reviewed science journals.

As well as the conference examples I mentioned above, peer-reviewed science journals have published papers on “xenoarchaeology” in all but name – defined as the search for physical remains of past non-human cultures. McGee’s paper focuses on xenoarchaeology in the solar system, what Robert Freitas terms SETA in his papers, but another active area of inquiry is the astronomical search for megascale engineering – “Dysonian SETI” as Milan Cirkovic calls it.

Another point in which I agree with Billings is that ‘the first step toward establishing credibility and authority for “xenoarchaeology” would be to create an international community of credible and authoritative “xenoarchaeologists.”’ – and this is part of what motivates me to promote the disparate fields which I think need to be brought together.

McGee’s paper may not have made a major contribution to the development of xenoarchaeology, but I’m glad to see it has attracted such a strong response. This review was written without having read McGee’s rejoinder.