Immortality

I am a huge fan of Feynman and agree with so many of his views, and am blown away by how articulate he is and how a scientist can think like an engineer (i.e., be practical)! But these lines from one of his lectures in 1964 surprised me:

“It is one of the most remarkable things that in all of the biological sciences there is no clue as to the necessity of death. If you say we want to make perpetual motion, we have discovered enough laws as we studied physics to see that it is either absolutely impossible or else the laws are wrong. But there is nothing in biology yet found that indicates the inevitability of death. This suggests to me that it is not at all inevitable.”

I was surprised by Feynman’s ignorance on this topic, so to speak. Let me elaborate.

Life rarely deals with individual anything (it is either about a combination of cells to form an organ, or a combination of organs to form an individual, or a combination of individuals to form a group/species). Further, pretty much nothing is studied in isolation: it is always a study of whatever is being observed in an environment that includes both physical and other biological elements.

Now apply the above point to death…via a “thought experiment”, something ironically that physicists love! Analyze a world where a particular species is immortal, i.e., the opposite of death. But first, I will assume that Feynman did not mean death as in the deer getting eaten by the lion. I am going to assume Feynman was talking about death due to “natural causes”, a body starting to shut down beyond a certain age.

To simplify the analysis, assume that this immortal species is at the top of the food chain, i.e., nobody eats it. The immediate problem such a species would run into it would be shortage of food and other resources since nobody dies but they do keep having children. Ok, to avoid that problem, let’s assume this immortal species is sterile. But no children means no genetic mutations can occur in the species. And without mutations, there’s no evolution (of that species, at least). Now it is impossible that a particular species is perfectly suited for all possible environments in the future? What if its natural food became extinct? Or what if its food evolved to have better defense mechanisms (maybe it grows thorns or maybe it outruns the immortal species)? Or what if the atmospheric composition changed and the fraction of whatever gas this immortal species needs dwindled?

So that answer to Feynman’s point is that there is no “necessity of death” in the biological sciences. Rather, the reason no species becomes immortal is that immortality is not an evolutionarily stable strategy (ESS).

But OK, I am going to assume Feynman didn’t know this because Richard Dawkins hadn’t published his book, The Selfish Gene, until 12 years after Feynman’s lecture.