Freeman Dyson's piece seems like pure madness to me. It is obviously written by someone who has no concept of biology. Plants based on silicon rather than chlorophyll? Come on. Since Dyson is a physicist, he might more productively turn his efforts to weakening the charge of the proton so that we can produce electricity at lower cost, or re-engineering the gravitational constant so that we don't expend so much energy transporting cargo. These proposals make about as much sense as his. And wouldn't be just a little cruel to have children and other free agents tinkering with the genomes of animals so as to produce dysmorphic and deranged living toys? Dyson has been at this for almost 20 years. The British philosopher of biology Mary Midgley raked him over the coals (along with some Left icons such as JBS Haldane and JD Bernal) in the excellent "Science as Salvation" (Routledge, 1992) for what she calls "quasi-scientific dreams and prophesies" involving visions of escape from the constraints of biology, coupled with "self-indulgent, uncontrolled power-fantasies."