Would Ron Breslow's dinosaurs be typing this post?

Much has been written about a recent perspective in JACS written by Ronald Breslow on the origin of homochirality during the origin of life. There's excellent commentary on the topic from See Arr Oh and Paul@Chembark. Briefly, Breslow's paper describes some pretty interesting research from his and other groups establishing a possible mechanism for the transfer of chirality from alpha-methyl amino acids to standard amino acids, followed by the amplification of that small chirality excess through a variety of plausible mechanisms involving the concentration of the dominant enantiomer.

The paper would have remained an interesting chemistry curiosity about the origin of life. It could have even served to remind the public that the origin of life is chemistry's Big Question, had it not been for two lines at the end of the piece:

"An implication of this work is that elsewhere in the universe there could exist life forms based on D amino acids and L sugars...Such life forms could even be advanced versions of dinosaurs,  if mammals did not have the good fortune to have the dinosaurs wiped out by an asteroidal collision, as on Earth. We would be better off not meeting them."

What was interesting was that when I first came across the paper, I spent about two seconds on this line and moved on. The line is an amusing attempt at humor. You usually don't see humor in a technical paper, but in fact I am all for it; I think we need to spice up our otherwise dry scientific literature with the occasional joke. The content of the paper obviously had nothing to do with dinosaurs; it was about a specific technical chemical puzzle in the origins of life. And nothing would have come out of it had not the ACS PR office created a sensationalized news piece wrongly centered around these two lines. Scant attention was paid to the scientific substance of the paper, and it didn't help when other popular venues like The Huffington Post also questioned Breslow about it and received the following answer:

"From there, Breslow makes the jump to advanced dinosaurs. But why might extraterrestrial life be in that form? “Because mammals survived and became us only because the dinosaurs were wiped out by an asteroid, so on a planet similar to ours without the asteroid collision it is unlikely that human types would be there, more probably advanced lizards (dinosaurs),” Dr. Breslow told The Huffington Post in an email."

This set of events led to some unfortunate consequences. For one thing, the undue emphasis on dinosaurs at the expense of homochirality was another nail in the coffin of the public communication of chemistry. Here was a chance to explain to the public why the origin of life is chemically fascinating, but instead the chemical substance got overwhelmed by the precipitate of publicity surrounding dinosaurs. If the ACS is wondering why chemistry is having such a PR problem, now would be the time to look in the mirror.

The situation was exacerbated by more serious matters. Following a tip from some commentators, Stu Cantrill of Nature Chemistry looked up two old Breslow papers on the same topic and found out an extreme case of self-plagiarism; most of the paper seems to have been copied verbatim from the other sources. Breslow should not be blamed for inserting that little joke at the end - it was the media which sensationalized it - but he cannot be excused for the gratuitous self-plagiarism.

That's about what I want to say about this unfortunate episode since others have extensively covered it, but I do want to focus on Breslow's reply to The Huffington Post. Some have chided him for it, but the statement is actually not as absurd as it sounds since Breslow is asking a famous, age-old question in evolutionary theory: If the tape of evolution were re-run, would it again produce dinosaurs, Breslow and ACS editors? Or in other words, how predetermined is evolution, and how dependent is it on accidents? This question is a profound one , since if the answer is even an affirmative "yes", it has serious implications for not just science but for theology and philosophy and the whole puzzle of human existence. 

Stephen Jay Gould was a powerful advocate of contingency in evolution, and his argument is not surprising to see. Evolution has been shaped by so many quirks of environment and the fate of individual organisms and species, that it would be naive to think that chance did not play a role in it. A single piece of wood accidentally drifting apart and carrying a few species on it to an isolated island can sculpt the evolution of that species. And we know for a fact that more massive events like volcanoes and earthquakes certainly did this. In fact it was geologist Charles Lyell's descriptions of such seismic events that started Darwin down the path to evolution and natural selection. It seems thus that if one could hypothetically run "what if" scenarios, it's very unlikely that anything approximating modern humans and dinosaurs could ever arise.

But this answer is not as obvious as it sounds. The biologist Simon Conway Morris has put forth a competing scenario in which certain universal features of evolution guarantee the presence of common adaptations during the evolution of species. This argument is based on what's called "convergent evolution" which essentially refers to the existence of common solutions to diverse evolutionary problems. A typical example would be all kinds of mammals, fish, amphibians and reptiles whose bodies are adapted to swimming. In most of these creatures you see similarly shaped, streamlined bodies, muscles and bones which are suited for swimming. Another principle concerns homologous structures (and not convergent evolution, as a commentator reminded me) like the digits of the hand, whose basic plan seems to be conserved across species. Indeed, homologous evolution provide some of the strongest pieces of evidence for common evolutionary origins. Thus Morris's argument is that even if the evolutionary tape were to run again, something similar to humans, dinosaurs, frogs and eagles (although the details would certainly differ) would be seen if the process were allowed to keep to itself for a few billion years. This interpretation acquires even greater significance when applied to humans; would such an intelligent, successful and self-centered species as Homo sapiens have evolved in an alternative evolutionary universe?

There is a lot of interesting discussion to be had about this topic. It's equally fascinating when applied to chemistry and leads to similar questions. For instance, what are the chances that the foundational compounds of life - DNA, RNA, amino acids, sugars, ATP - would have formed had evolution been left to run again with different tweaks and quirks of fate? Personally I find the questions somewhat easier to answer in case of chemistry since the formation of many of these compounds is governed by relatively simple energetic arguments. ATP's express purpose is to make otherwise unfavorable reactions possible by driving them downhill through high-energy bonds, and if not ATP it's hard to see how some other chemical compounds performing the same function could not have evolved. A great example of an attempt to answer these questions is seen in Frank Westheimer's classic paper "Why Nature Chose Phosphates?" in which he points to the unique properties of phosphate that make it such a dominant source in life's workings, both in metabolism and heredity.

Breslow's question is therefore quite sensible and its implications are fascinating to ponder. How would 2012 have looked like had the dinosaurs not been wiped out by an asteroid? Would they still have been alive and would humans have had the unfortunate fate of co-existing with them? Would they be as smart as humans? Naturally such scenarios would have profoundly affected the evolution and character of our civilization. Or would the dinosaurs have precluded the rise of Homo sapiens, perhaps by nipping our scarce population in the bud and making us extinct? Or would they have become extinct themselves through some other cause, perhaps extreme climate change? How indeed would planet earth have looked like had it still been ruled by dinosaurs?

Naturally we don't know the answers to these questions. But Breslow's little joke at the end, while sounding silly, inadvertently asks a very important and thought-provoking question. Too bad it was all obscured by the charges of self-plagiarism.