I am a sentient anaerobic multicellular organism whose ability to survive and prosper in an oxygen-rich environment is dependent on an ancient symbiosis with aerobic bacteria that live permanently within my cells (see http://setiathome.ssl.berkeley.edu/cgi-bin/cgi?cmd=view_feedback&id=7608). These bacteria are irrevocably bound to the symbiotic contract by the loss of erstwhile vital genomic code that had become redundant through access to the transcriptional products of my own.
Forty five years ago I was provided with a colony of these attenuated bacteria by my mother. Since then these bacteria and my somatic cells have faced inevitable mortality. Terminal evolutionary failure has been avoided by half of the genome in three of my germ cells but the bacterial symbionts that enabled the delivery of this genomic cargo to a totipotent haploid anaerobic cell perished at the end of their mission.
I secure the raw materials required for our temporary survival but my intracellular bacterial symbionts expedite most of the energy transformation and entropic management required for our mutual metabolic needs.
I salute my bacterial symbionts and acknowledge that our world largely belongs to protistans such as them, with metazoans comprising an interesting but minor component of the biomass of our planet.
Thoughts about SETI and SETI@home
Chemical species that are characterised by a propensity to form copies of themselves will do so for no reason other than that they are compelled to behave in that way by the fortuitous arrangement of electrons in their outer shells. There is no justifiable reason for excluding such systems from the set of "living" things. Any two different self-replicating systems that share an environment will passively compete for those raw materials that are required by both for replication so evolution is inevitable. Any system large enough to support sufficient raw materials to allow repeated generations of molecular copies is a potential cradle of life. The presence of a suitable source of energy to facilitate the reactions that comprise self-replication provides an opportunity for such cradles of life to realise their potential. Self-replicating chemical systems, repositories of raw materials and sources of energy abound in the observable universe.
Viewed in this way it seems probable that life is widespread and its presence in any locale (on a cosmic scale) is the rule rather than the exception. Self-replicating systems may remain dispersed within a chemical soup or may organise in discrete units. Discrete units may remain isolated or may associate in large colonies as survival machines. Large colonies may remain generally solitary or may form socially structured metacolonies.
We are unlikely to discover whether living systems other than our own have found evolutionary advantage in advanced intelligence unless we look. Let's look. Let's anounce to the cosmos the presence of one living system that has evolved in this way. Let's not be distracted by imagined dangers. Like our own bacterial symbionts let's act without malice for the good of the universe.
SETI@home and Astropulse are funded by grants from the National Science Foundation, NASA, and donations from SETI@home volunteers. AstroPulse is funded in part by the NSF through grant AST-0307956.
