In the Commentary 'Common sense for our genomes' (Nature 449, 783–784; 2007), Steven Brenner welcomes the sequencing of the genomes of James Watson and Craig Venter. Although the generally hypothesis-free collection of large amounts of sequence information may indeed turn out to be important, caution is warranted.

First, it is not the static genome but rather the dynamic proteome that regulates the enormous changes occurring in an organism between conception and death. Second, only the most radical reductionist would argue that a person's essence can be captured by his or her proteome, let alone his or her genome.

Our lives are unrepeatable experiments lacking a control. Myriad external factors interact with genetic and epigenetic factors and with chance to determine whether we are well or ill, smart or dull, successes or failures. A study on some 44,000 twin pairs concluded that environmental and not inherited genetic factors were the main determinants of sporadic cancer (P. Lichtenstein et al. N. Engl. J. Med. 343, 78–85; 2000). Brute-force genome sequencing and Brenner's proposed Genome Commons could yield nonsense if environmental factors are overlooked.

This is not just an academic issue. Membership of the 'diploid genome club' is set to rise rapidly (see Nature 447, 358–359; 2007). The X Prize Foundation is offering the Archon genomics prize of US$10 million to the first team able to sequence 100 human genomes accurately within ten days. But whether the winners will understand the results is a different question entirely.