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Reasons To Believe Home PageIn case you haven’t already met it, let me introduce you to a new field of science research, "comparative genomics." This new line of inquiry has been made possible by our recently acquired capability to chart all the nucleotides in all the genes of an organism. To date, complete genome sequences for four different species have been mapped out, and these four give us representation from each of the three "domains" of life.(1-4) If you went to school more than a decade or two ago, you were taught that life could e divided into two kingdoms, plant and animal. Today biologists refer to living things as eukaryote (including plant, animal, and fungus life), prokaryote (bacterial life), or achaeon (microscopic life found near oceanic thermal vents and elsewhere). These domains are distinguished by the way the various species’ genetic material (DNA) is stored or configured.
The two prokaryote (or bacteria) species were chosen for complete genome analysis because of vast differences in their morphology and genetic composition. Haemophilus influenza contains about 1,700 genes; Mycoplasma genitalium contains only 470 genes, the smallest number yet discovered for any species. Arcady Mushegian and Eugen Koonin of the National Center for Biotechnology Information reasoned that any genes such diverse species hold in common are likely essential for basic cell function. That number adds up to 240. To cover certain enzyme functions critical for cell survival, they add 22 genes, for a total of 262, then they trim out 6 genes that appear redundant or specific to each bacteria’s adaptation for feeding on its specific host. Their final figure, then, for the miminum genome to support cell function and reproduction is 256.(5)
Referring to their calculation as preliminary, Mushegian and Koonin realize they may have over-looked some critical function(s) not covered by the 256 genes. Clearly, the bacteria do have to find and attach to suitable hosts, and some level of genetic redundancy appears essential for species’ survival. When complete genome analysis for more species, including humans, becomes available in a few months, a more accurate estimate of life’s minimal chemical complexity will also be available. But in the meantime, Mushegian and Koonin’s work provides a ballpark figure for determining the magnitude of the "spontaneous generation" problem. Anyone proposing a naturalistic interpretation for life’s origin must be able to explain how 256+ genes, plus all the other chemical components and structures for survival and reproduction put themselves together via mindless, purposeless, non-organic processes.
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