Skip to main content Accessibility help

SETI in vivo: testing the we-are-them hypothesis

  • Maxim A. Makukov (a1) and Vladimir I. shCherbak (a2)


After it was proposed that life on Earth might descend from seeding by an earlier extraterrestrial civilization motivated to secure and spread life, some authors noted that this alternative offers a testable implication: microbial seeds could be intentionally supplied with a durable signature that might be found in extant organisms. In particular, it was suggested that the optimal location for such an artefact is the genetic code, as the least evolving part of cells. However, as the mainstream view goes, this scenario is too speculative and cannot be meaningfully tested because encoding/decoding a signature within the genetic code is something ill-defined, so any retrieval attempt is doomed to guesswork. Here we refresh the seeded-Earth hypothesis in light of recent observations, and discuss the motivation for inserting a signature. We then show that ‘biological SETI’ involves even weaker assumptions than traditional SETI and admits a well-defined methodological framework. After assessing the possibility in terms of molecular and evolutionary biology, we formalize the approach and, adopting the standard guideline of SETI that encoding/decoding should follow from first principles and be convention-free, develop a universal retrieval strategy. Applied to the canonical genetic code, it reveals a non-trivial precision structure of interlocked logical and numerical attributes of systematic character (previously we found these heuristically). To assess this result in view of the initial assumption, we perform statistical, comparison, interdependence and semiotic analyses. Statistical analysis reveals no causal connection of the result to evolutionary models of the genetic code, interdependence analysis precludes overinterpretation, and comparison analysis shows that known variations of the code lack any precision-logic structures, in agreement with these variations being post-LUCA (i.e. post-seeding) evolutionary deviations from the canonical code. Finally, semiotic analysis shows that not only the found attributes are consistent with the initial assumption, but that they make perfect sense from SETI perspective, as they ultimately maintain some of the most universal codes of culture.


Corresponding author


Hide All
Ahituv, N., Zhu, Y., Visel, A., Holt, A., Afzal, V., Pennacchio, L.A. & Rubin, E.M. (2007). Deletion of ultraconserved elements yields viable mice. PLoS Biol. 5, e234.
Amirnovin, R. (1997). An analysis of the metabolic theory of the origin of the genetic code. J. Mol. Evol. 44, 473476.
Anglada-Escude, G. et al. (2014). Two planets around Kapteyn's star: a cold and a temperate super-Earth orbiting the nearest halo red dwarf. Mon. Not. R. Astron. Soc. Let. 443, L89L93.
Bains, W. & Schulze-Makuch, D. (2016). The cosmic zoo: the (near) inevitability of the evolution of complex, macroscopic life. Life 6, 25.
Baranov, P.V., Atkins, J.F. & Yordanova, M.M. (2015). Augmented genetic decoding: global, local and temporal alterations of decoding processes and codon meaning. Nat. Rev. Genet. 16, 517529.
Bell, E.A., Boehnke, P., Harrison, T.M. & Mao, W.L. (2015). Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon. Proc. Natl. Acad. Sci. USA 112, 1451814521.
Brar, G.A. (2016). Beyond the triplet code: context cues transform translation. Cell 167, 16811692.
Campante, T.L. et al. (2015). An ancient extrasolar system with five sub-Earth-size planets. Astrophys. J. 799, 170.
Chin, J.W. (2014). Expanding and reprogramming the genetic code of cells and animals. Annu. Rev. Biochem. 83, 379408.
Chrisomalis, S. (2010). Numerical Notation: A Comparative History. Cambridge University Press, Cambridge.
Ćirković, M.M. (2014). Evolutionary contingency and SETI revisited. Biol. Philos. 29, 539557.
Conway Morris, S. (2003a). Life's Solution: Inevitable Humans in a Lonely Universe. Cambridge University Press, Cambridge.
Conway Morris, S. (2003b). The navigation of biological hyperspace. Int. J. Astrobiol. 2, 149152.
Conway Morris, S. (2011). Predicting what extra-terrestrials will be like: and preparing for the worst. Phil. Trans. R. Soc. A 369, 555571.
Crick, F.H.C. (1981). Life Itself: Its Origin and Nature. Simon & Schuster, New York.
Crick, F.H.C. & Orgel, L.E. (1973). Directed panspermia. Icarus 19, 341346.
Danckwerts, H.J. & Neubert, D. (1975). Symmetries of genetic code-doublets. J. Mol. Evol. 5, 327332.
Dantzig, T. (1954). Number: The Language of Science, 4th edn. Simon & Schuster, New York.
Davies, P.C.W. (2012). Footprints of alien technology. Acta Astronaut. 73, 250257.
Davis, J. (1996). Microvenus. Art. J. 55, 7074.
Dawkins, R. (2004). The Ancestor's Tale: A Pilgrimage to the Dawn of Life. Houghton Mifflin Harcourt, Boston.
de Grijs, R. (2010). A revolution in star cluster research: setting the scene. Phil. Trans. R. Soc. A 368, 693711.
Deacon, T.W. (1997). The Symbolic Species: The Co-evolution of Language and the Brain. W.W. Norton & Co, New York.
Di Giulio, M. (2004). The coevolution theory of the origin of the genetic code. Phys. Life Rev. 1, 128137.
Doolittle, W.F. (2000). The nature of the universal ancestor and the evolution of the proteome. Curr. Opin. Struct. Biol. 10, 355358.
Forterre, P. & Philippe, H. (1999). Where is the root of the universal tree of life? BioEssays 21, 871879.
Fournier, G.P. & Gogarten, J.P. (2007). Signature of a primitive genetic code in ancient protein lineages. J. Mol. Evol. 65, 425436.
Freeland, S.J. & Hurst, L.D. (1998). The genetic code is one in a million. J. Mol. Evol. 47, 238248.
Freitas, R.A. (1983). The search for extraterrestrial artifacts (SETA). J. Br. Interplanet. Soc. 36, 501506.
Gazalé, M. (2000). Number: From Ahmes to Cantor. Princeton University Press, Princeton.
Gibbs, W.W. (2001). Art as a form of life. Sci. Am. 284, 3739.
Gibson, D.G. et al. (2010). Creation of a bacterial cell controlled by a chemically synthesized genome. Science 329, 5256.
Giegé, R. (2008). Toward a more complete view of tRNA biology. Nat. Struct. Mol. Biol. 15, 10071014.
Glansdorff, N., Xu, Y. & Labedan, B. (2008). The last universal common ancestor: emergence, constitution and genetic legacy of an elusive forerunner. Biol. Dir. 3, 29.
Gould, S.J. (1985). The Flamingo's Smile: Reflections in Natural History. Norton & Co, New York.
Gould, S.J. (1989). Wonderful life: The Burgess Shale and the Nature of History. Norton & Co, New York.
Gros, C. (2016). Developing ecospheres on transiently habitable planets: the genesis project. Astrophys. Space Sci. 361, 324.
Guo, M. & Schimmel, P. (2013). Essential nontranslational functions of tRNA synthetases. Nat. Chem. Biol. 9, 145153.
Haldane, J.B.S. (1954). The origins of life. New Biol. 16, 1227.
Hasegawa, M. & Miyata, T. (1980). On the antisymmetry of the amino acid code table. Orig. Life 10, 265270.
Hayes, B. (1998). The invention of the genetic code. Am. Sci. 86, 814.
Hoch, J.A. & Losick, R. (1997). Panspermia, spores and the Bacillus subtilis genome. Nature 390, 237238.
Hoffman, D.C., Anderson, R.C., DuBois, M.L. & Prescott, D.M. (1995). Macronuclear gene-sized molecules of hypotrichs. Nucleic Acids Res. 23, 12791283.
Ifrah, G. (2000). The Universal History of Numbers: From Prehistory to the Invention of the Computer. John Wiley & Sons, New York.
Ilardo, M., Meringer, M., Freeland, S.J., Rasulev, B. & Cleaves, H.J. 2nd (2015). Extraordinarily adaptive properties of the genetically encoded amino acids. Sci. Rep. 5, 9414.
Isenbarger, T.A., Carr, C.E., Johnson, S.S., Finney, M., Church, G.M., Gilbert, W., Zuber, M.T. & Ruvkun, G. (2008). The most conserved genome segments for life detection on Earth and other planets. Orig. Life Evol. Biosph. 38, 517533.
Ivanova, N.N., Schwientek, P., Tripp, H.J., Rinke, C., Pati, A., Huntemann, M., Visel, A., Woyke, T., Kyrpides, N.C. & Rubin, E.M. (2014). Stop codon reassignments in the wild. Science 344, 909913.
Kaplan, R. (1999). The Nothing That Is: A Natural History of Zero. Oxford University Press, Oxford.
Knight, R.D., Freeland, S.J. & Landweber, L.F. (1999). Selection, history and chemistry: the three faces of the genetic code. Trends Biochem. Sci. 24, 241247.
Knight, R.D., Freeland, S.J. & Landweber, L.F. (2001). Rewiring the keyboard: evolvability of the genetic code. Nat. Rev. Genet. 2, 4958.
Koonin, E.V. (2011). The Logic of Chance: The Nature and Origin of Biological Evolution. FT Press, Upper Saddle River.
Koonin, E.V. & Novozhilov, A.S. (2009). Origin and evolution of the genetic code: the universal enigma. IUBMB Life 61, 99111.
Koonin, E.V. & Novozhilov, A.S. (2017). Origin and evolution of the universal genetic code. Annu. Rev. Genet 51. doi: 10.1146/annurev-genet-120116-024713.
Kouwenhoven, M.B.N., Shu, Q., Cai, M.X. & Spurzem, R. (2016). Planetary systems in star clusters. Proc. Cosmic-Lab: Star Clusters as Cosmic Laboratories for Astrophysics, Dynamics, and Fundamental Physics - MODEST16. arXiv:1609.00898 [astro-ph.EP].
Lagerkvist, U. (1978). ‘Two out of three’: an alternative method for codon reading. Proc. Natl. Acad. Sci. USA 75, 17591762.
Lajoie, M.J., Kosuri, S., Mosberg, J.A., Gregg, C.J., Zhang, D. & Church, G.M. (2013). Probing the limits of genetic recoding in essential genes. Science 342, 361363.
Lajoie, M.J., Söll, D. & Church, G.M. (2016). Overcoming challenges in engineering the genetic code. J. Mol. Biol. 428, 10041021.
Lemarchand, G. & Lomberg, J. (2009). Universal cognitive maps and the search for intelligent life in the universe. Leonardo 42, 396402.
Lineweaver, C.H. (2001). An estimate of the age distribution of terrestrial planets in the universe: quantifying metallicity as a selection effect. Icarus 151, 307313.
Liu, C.C. & Schultz, P.G. (2010). Adding new chemistries to the genetic code. Annu. Rev. Biochem. 79, 413444.
Lobkovsky, A.E. & Koonin, E.V. (2012). Replaying the tape of life: quantification of the predictability of evolution. Front. Genet. 3, 18.
Lotman, Yu. M., Uspensky, B.A. & Mihaychuk, G. (1978). On the semiotic mechanism of culture. New Lit. Hist. 9, 211232.
Makukov, M.A. & shCherbak, V.I. (2014). Space ethics to test directed panspermia. Life Sci. Space Res. 3, 1017.
Maraia, R.J. & Iben, J.R. (2014). Different types of secondary information in the genetic code. RNA 20, 977984.
Martínez-Barbosa, C.A., Brown, A.G.A., Boekholt, T., Portegies Zwart, S., Antiche, E. & Antoja, T. (2016). The evolution of the Sun's birth cluster and the search for the solar siblings with Gaia. Mon. Not. R. Astron. Soc. 457, 10621075.
Marx, G. (1979). Message through time. Acta Astronaut. 6, 221225.
Marx, G. (1986). The problem of simultaneity. In The Problem of the Search for Life in the Universe: Proceedings of the SETI Symposium in Tallinn, ed. Ambartsumian, V.A., Kardashev, N.S. & Troitsky, V.S., pp. 7481. Nauka, Moscow (in Russian).
Massey, S.E. (2016). The neutral emergence of error minimized genetic codes superior to the standard genetic code. J. Theor. Biol. 408, 237242.
Mautner, M.N. (1997). Directed panspermia. 3. Strategies and motivation for seeding star-forming clouds. J. Brit. Interplanet. Soc. 50, 93102.
Mautner, M.N. (2000). Seeding the Universe with Life: Securing Our Cosmological Future. Legacy Books, Weston.
Mautner, M.N. (2009). Life-centered ethics, and the human future in space. Bioethics 23, 433440.
Mazur, J. (2014). Enlightening Symbols: A Short History of Mathematical Notation and its Hidden Powers. Princeton University Press, Princeton.
McGhee, G. (2011). Convergent Evolution: Limited Forms Most Beautiful. The MIT Press, London.
Melosh, H.J. (2003). Exchange of meteorites (and life?) between stellar systems. Astrobiology 3, 207215.
Meot-Ner, M. & Matloff, G.L. (1979). Directed panspermia – a technical and ethical evaluation of seeding nearby solar systems. J. Br. Interplanet. Soc. 32, 419423.
Meyer, F., Schmidt, H.J., Plümper, E., Hasilik, A., Mersmann, G., Meyer, H.E., Engström, A. & Heckmann, K. (1991). UGA is translated as cysteine in pheromone 3 of Euplotes octocarinatus. Proc. Natl. Acad. Sci. USA 88, 37583761.
Mileikowsky, C., Cucinotta, F.A., Wilson, J.W., Gladman, B., Horneck, G., Lindegren, L., Melosh, J., Rickman, H., Valtonen, M. & Zheng, J.Q. (2000). Natural transfer of viable microbes in space. 1. From Mars to Earth and Earth to Mars. Icarus 145, 391427.
NC-IUB – Nomenclature Committee of the International Union of Biochemistry (1985). Nomenclature for incompletely specified bases in nucleic acid sequences: recommendations 1984. Nucleic Acids Res. 13, 30213030.
Novozhilov, A.S., Wolf, Y.I. & Koonin, E.V. (2007). Evolution of the genetic code: partial optimization of a random code for robustness to translation error in a rugged fitness landscape. Biol. Dir. 2, 24.
Ostrov, N. et al. (2016). Design, synthesis, and testing toward a 57-codon genome. Science 353, 819822.
Pfalzner, S. (2013). Early evolution of the birth cluster of the solar system. Astron. Astrophys. 549, A82.
Philip, G.K. & Freeland, S.J. (2011). Did evolution select a nonrandom ‘alphabet’ of amino acids? Astrobiology 11, 235240.
Plotkin, J.B. & Kudla, G. (2011). Synonymous but not the same: the causes and consequences of codon bias. Nat. Rev. Genet. 12, 3242.
Roberts, F.S. & Tesman, B. (2009). Applied Combinatorics. CRC Press, Boca Raton.
Rodin, A.S., Szathmáry, E. & Rodin, S.N. (2011). On origin of genetic code and tRNA before translation. Biol. Dir. 6, 14.
Ronneberg, T.A., Landweber, L.F. & Freeland, S.J. (2000). Testing a biosynthetic theory of the genetic code: fact or artifact? Proc. Natl. Acad. Sci. USA 97, 1369013695.
Rospars, J.-P. (2010). Terrestrial biological evolution and its implication for SETI. Acta Astronaut. 67, 13611365.
Rumer, Y.B. (1966). Systematization of codons in the genetic code. Proc. USSR Acad. Sci. 167, 13931394 (in Russian).
Rumer, Y.B. (2016). Translation of ‘Systematization of codons in the genetic code [I]’ by Yu. B. Rumer (1966). Phil. Trans. R. Soc. A 374, 20150446.
Sagan, C., Drake, F., Druyan, A., Ferris, T., Lomberg, J. & Sagan, L.S. (1978). Murmurs of Earth: The Voyager Interstellar Record. Random House, New York.
Sebeok, T.A. (2001). Signs: An Introduction to Semiotics, 2nd edn. University of Toronto Press, Toronto.
Seife, C. (2000). Zero: The Biography of a Dangerous Idea. Penguin Books, New York.
Shcherbak, V.I. (1988). The co-operative symmetry of the genetic code. J. Theor. Biol. 132, 121124.
Shcherbak, V.I. (1989). The information artefact of the genetic code. Orig. Life Evol. Biosph. 19, 364365.
shCherbak, V.I. & Makukov, M.A. (2013). The ‘Wow! signal’ of the terrestrial genetic code. Icarus 224, 228242.
Shklovskii, I.S. & Sagan, C. (1966). Intelligent Life in the Universe. Holden-Day, San Francisco.
Sleator, R. & Smith, N. (2017). Directed panspermia: a 21st century perspective. Sci. Prog. 100, 187193.
Sukhotin, B.V. (1971). Methods of message decoding. In Extraterrestrial Civilizations: Problems of Interstellar Communication, ed. Kaplan, S.A., pp. 133212. NASA Technical Translations, F-631 (translated from Russian, 1969, Nauka, Moscow).
Swart, E.C., Serra, V., Petroni, G. & Nowacki, M. (2016). Genetic codes with no dedicated stop codon: context-dependent translation termination. Cell 166, 691702.
Tepfer, D. (2008). The origin of life, panspermia and a proposal to seed the Universe. Plant Sci. 175, 756760.
Vakoch, D.A. (1998a). Constructing messages to extraterrestrials: an exosemiotic perspective. Acta Astronaut. 42, 697704.
Vakoch, D.A. (1998b). Signs of life beyond Earth: a semiotic analysis of interstellar messages. Leonardo 31, 313319.
Vakoch, D.A. (2011). Responsibility, capability, and Active SETI: policy, law, ethics, and communication with extraterrestrial intelligence. Acta Astronaut. 68, 512519.
Vakoch, D.A. (eds) (2014). Extraterrestrial Altruism: Evolution and Ethics in the Cosmos. Springer, Berlin.
Valtonen, M., Nurmi, P., Zheng, J.Q., Cucinotta, F.A., Wilson, J.W., Horneck, G., Lindegren, L., Melosh, J., Rickman, H. & Mileikowsky, C. (2009). Natural transfer of viable microbes in space from planets in extra-solar systems to a planet in our solar system and vice versa. Astrophys. J. 690, 210215.
Ward, P.D. & Brownlee, D. (2003). Rare Earth: Why Complex Life Is Uncommon in the Universe. Copernicus Books, New York.
Webb, S. (2015). If the Universe Is Teeming with Aliens … Where Is Everybody? Seventy-Five Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life, 2nd edn. Springer.
Weiss, M.C., Sousa, F.L., Mrnjavac, N., Neukirchen, S., Roettger, M., Nelson-Sathi, S. & Martin, W.F. (2016). The physiology and habitat of the last universal common ancestor. Nat. Microbiol. 1, 16116.
Wilhelm, T. & Nikolajewa, S. (2004). A new classification scheme of the genetic code. J. Mol. Evol. 59, 598605.
Wong, J.T.-F. (1975). A co-evolution theory of the genetic code. Proc. Natl. Acad. Sci. USA 72, 19091912.
Wong, P.C., Wong, K. & Foote, H. (2003). Organic data memory using the DNA approach. Commun. ACM 46, 9598.
Yarus, M., Widmann, J.J. & Knight, R. (2009). RNA-amino acid binding: a stereochemical era for the genetic code. J. Mol. Evol. 69, 406429.
Yokoo, H. & Oshima, T. (1979). Is bacteriophage φX174 DNA a message from an extraterrestrial intelligence? Icarus 38, 148153.
Zaitsev, A. (2012). Classification of interstellar radio messages. Acta Astronaut. 78, 1619.
Zhang, J. & Norman, D.A. (1995). A representational analysis of numeration systems. Cognition 57, 271295.
Zhang, Z. & Yu, J. (2011). On the organizational dynamics of the genetic code. Genomics Proteomics Bioinformatics 9, 2129.


Related content

Powered by UNSILO
Type Description Title
Supplementary materials

Makukov and shCherbak supplementary material
Video 1

 Video (144.6 MB)
144.6 MB
Supplementary materials

Makukov and shCherbak supplementary material
Video 2

 Video (21.6 MB)
21.6 MB

SETI in vivo: testing the we-are-them hypothesis

  • Maxim A. Makukov (a1) and Vladimir I. shCherbak (a2)


Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed.