Hoyle and Wickramasinghe

More from the book I mentioned last week.

Some species have "evolutionary potential" and others don't. Some have come to an evolutionary dead end. That distinction has some support from Ohno.

Among those species with EP, the potential becomes actual when there is a shock from without, a benevolent infection.

"It is interesting that among birds those in which influenza virus has been found -- chicken, duck, turkey, quail, shearwater -- tend to be long-lived species. We remarked above that program changes which are not improvements show up as disease, from which it follows that species susceptible to program changes -- i.e. those stil with evolutionary potentisal -- must exhibit a greater tendency to disease than static spcies without evolutionary potential."