Bob, thanks, just seeing this. I didn't propose a model, but a challenge to produce a model. There's a webpage about the challenge, titled "The Evolution Prize," on my panspermia website at http://www.panspermia.org/eprize.htm. The prize also had its own website, linked from there, maintained for 2 years. There's criticism on the discussion page there. In sum, the idea met with skepticism and distrust and never took off. I am still interested.