That's bad, because the most interesting breakthroughs came from cross-disciplinary work.
The cross-disciplinary breakthrough is often characterized as unifying, and hence rightfully celebrated. But they are neither the norm nor the most influential.
Crick, Hodgkin and Huxley were all physicists poaching in other fields. In fact, relatively few of the people who laid the foundations in molecular biology were trained as biologists.
This recollection is incorrect across the board.
Crick had only a bachelors in physics (which does not a physicist make), and his postgraduate training was in medical research. Huxley, an autodidact, had his background in medicine. I'm not sure about Hodgkin but I suspect he was also not a physicist.
I admit that Hodgkin and Huxley are harder cases: both had early inclinations to physics and then got sidetracked into physiology. Both of them spent the war doing things you'd have a physicist doing during a war, and afterwards did their their famous work on the action potential. I read the Hodgkin and Huxley papers, but I read them in a course in the math department-- they contain some of history's finest examples of mathematical modeling, relying heavily on dynamical systems and circuit theory. It is a regrettably rare biologist who wants to go near those papers. It is manifestly not the work of traditionally trained biologists.
Disciplinary boundaries in mid-century Britain were somewhat different then, and I realize the danger of playing No True Biologist. But the mainstream of biology is only very recently acknowledging the importance of the physical approach: Hodgkin and Huxley could have been Hodgkin and Huxley without a lick of genetics or ethology, but they couldn't have been Hodgkin and Huxley without the cable equation.
I would also add Max Delbruck to your list of turn of the last century physicists cum molecular biologists and the physicist members of the RNA tie club: http://en.wikipedia.org/wiki/RNA_Tie_Club.
I also have a question for the GP. What exactly makes a physicist so? I have "merely" a masters degree in physics, and although I consider myself to be a theoretical biologist, I am often called a physicist by my collaborators (some of whom are physicists themselves). What about a degree actually matters in this descriptive title?
And Fisher was a statistician.
I'm glad physicists can try their luck at AI. I'd be glad other disciplines, even remote, do too. Foreign concepts often bring with them new outlooks on problems that are very fertile and rejuvenating. A little bit more humility wouldn't hurt though.
True, but I think the signal-to-noise ratio is also exceptionally low. The most amazing breakthroughs come from insights that span disciplines, but it's also easy to think you have an insight when what you really have is a mistake. I'm not weighing in on this one in particular, but as a general principle I think caution is appropriate in cases like this.