Good Enough by Daniel S. Milo

Author:Daniel S. Milo
Language: eng
Format: epub
Publisher: Harvard University Press

Figure 6.5. The C-value paradox demonstrates waste in nature: There is no correlation between genome size and organism complexity. The flower Utricularia gibba has 82 million DNA base pairs; Homo sapiens have 3 billion; marbled lungfish (Protopterus aethiopicus) have 130 billion; and another flower, Paris japonica, has 150 billion.

It is also quite possible that what seems useless one day will be proven essential the next. Science is, after all, an ongoing project, and what we now know will be revised and augmented as more work gets done. Some of that work should and will entail studying highly conserved DNA segments to figure out what, if anything, they do and why. A good example is lacA, one of the three structural genes of the lac operon, which allows Escherichia coli to metabolize lactose in the absence of glucose. Since the operon’s discovery in the late 1950s—a pioneering moment in molecular biology—it has been unclear why lacA encodes the enzyme β-galactoside transacetylase, itself of no apparent value. As Jacques Monod, co-discoverer of the operon, told the audience assembled for his acceptance of the Nobel Prize, this gene “has been very useful to experimenters, if not to the bacterium itself.”50 But lacA is a ubiquitous and enduring feature of a critical living structure, so by all means, let us speculate about its purpose and seek evidence to support our theories. The search for significance—the war against neutrality—is the cornerstone of science.

But we should at least keep our presumptions straight. It will not do simply to ignore the evidence of excess before us: the DNA is not optimized but rather shot through with inefficiency. The quantity of uselessness grows with every germinal replication. Utility should be surprising, not the default assumption; that should be neutrality.

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