From Ralf Dahm
Penny Sarchet raises the tantalising possibility that life on our planet emerged not once but several times (20 August, p 26). Recently, DNA sequencing has detected microbial life that resists being cultured.
What if there is life that uses a different chemistry to store genetic information? The probability of such “alternative” life having survived the competition with DNA-based organisms is vanishingly small. But what a discovery it would be!
Mainz, Germany
