Can we define “life” in just three words? Carl Zimmer of Loom fame has written a piece for Txchnologist in which he reports on an interesting attempt: biologist Edward Trifonov looked at other people’s definitions, rather than thinking about life itself. Sifting through over a hundred suggested definitions, Trifonov looked for what they had in common, and boiled life down to “self-reproduction with variations.” Just three words, although one of them is compound so I would argue that morally it’s really four.
We’ve discussed this question before, and the idea of reproduction looms large in many people’s definitions of life. But I don’t think it really belongs. If you built an organism from scratch, that was as complicated and organic and lifelike as any living thing currently walking this Earth, except that it had no reproductive capacity, it would be silly to exclude it from “life” just because it was non-reproducing. Even worse, I realized that I myself wouldn’t even qualify as alive under Trifonov’s definition, since I don’t have kids and don’t plan on having any. (And no, those lawsuits were frivolous and the court records were sealed.)
It’s the yellow-taxi problem: in a city where all cars are blue except for taxis, which are yellow, it’s tempting to define “taxi” as “a yellow car.” But that doesn’t get anywhere near the essence of taxi-ness. Likewise, living species generally reproduce themselves; but that’s not really what makes them alive. Not that I have the one true definition (and maybe there shouldn’t be one). But any such definition better capture the idea of an ongoing complex material process far from equilibrium, or it’s barking up the wrong Tree.
“I don’t have kids and don’t plan on having any”
Joining the prestigious company of Steven Pinker. Since you publicly state your wish not to have children, I suppose it’s fair to ask what the reasons for it are. Consider that you are, compared to most people, in a much better position to have children. Also, there are many successful cosmologists (Barrow, Hawking, Sciama, Peebles—probably many more, but I don’t always know how many children people have) who have many children.
“I don’t have kids and don’t plan on having any”
Plans are just that plans. Plans are the back-up, there is the surprise factor that only nature controls.
It seems to me that when you talk about “building an organism from scratch” there is some presupposition that you can separate an organism from its environment. However, from what I understand, such mechanisms as adaptation and selection are functions of the environment, and therefore creating such an organism would not be observationally replicable for all intents and purposes. You would have to identify an organism that is as evolved and sufficiently complex as modern observed organisms, but without reproduction with heritable traits. But the last the time I checked, such mechanisms as adaptation and selection work through the gateway of reproduction with heritable traits, and these are in turn a function of the environment. Has your “from scratch” organism ever been observed and how would you go about identifying it as such? How would such a “from scratch” organism come into existence?
On the cellular level, reproduction is absolutely necessary, but on the larger level you’re right: reproduction cannot constitute life. If it did, mules (combination of horse and donkey that always results in a sterile animal) wouldn’t be considered alive.
There’s certainly life without reproduction. I therefore conclude by saying this three-letter sentence: “Go fuck yourselves!”
I would say that life requires reproduction, and that if it is made up of components that are alive (and reproduce), then it is alive even if it itself does not reproduce.
Of course, by this definition, societies and civilizations would qualify for being alive, but in my opinion, they are.
has anyone noticed that evolving life has the symmetry SU(3)? four DNA building blocks for each parent, or 8 total. this is what Steven Wildberg called the 8 fold way, for the above aymmetry.This is interesting in view of fact that there are 8 basic kinds of non decaying matter (electron, neutrino, proton and dueteron plus their antiparticles}
“Are you of a kind that has the capacity to reproduce” rather than “have you reproduced” is how I take the definition, so I’m comfortable allowing that Sean is probably alive. However, a thing must die in order to have ever been alive. Any ongoing complex material process operating far from equilibrium that neither stops (dies) nor has the ability to reproduce is… yet to be observed in nature?