Thursday, July 25, 2013

Science Writing In India And Some Thoughts On Punctuated Equilibrium

Kind of a hodge podge title but I didn't feel like writing two separate posts.

Current Science had a special focus a couple of weeks ago on science writing in India. Seema Singh has written quite well about her struggles to become a better science writer. She summarizes the state of science writing in India:

Science is just about reviving in India. People mention that the first time in three decades such a coordinated effort is being mounted to infuse funds and sparkle in Indian science. But there still are not too many stories that can be told with a single-sentence punch line. In which case, the art of chronicling the process becomes even more important. Now, whether the body of knowledge will help here, or the skill of storytelling, is left to my mind, to individual communicators, specialists or non-specialists. For me, personally, it is about homework and humility, intricate osmosis of critical inquiry and sensitivity, the spirit of curiosity, sense of wonder, and, of course, fact checking.

That's an important point about what and how science gets covered. Far too often, the media either exults in and tries to claim an Indian connection to a notable piece of research by an Indian scientist who left the country 20 years ago, or features scientists based in India only during satellite launches, nuclear power plant protests or major earthquakes. Science as an activity and scientists in their day to day working avatar are rarely featured.  A trigger to change this could come from within too. Few Indian scientists today are using social media platforms to initiate a conversation with the public. There has been a small increase in the number of Indian scientists who do blog with biologists and ecologists (1, 2) taking the lead, but my impression is that far too many write about everything else but their research.

Seema Singh also writes about her interesting encounter back in 2001 with evolutionary paleontologist Stephen Jay Gould who popularized the field of evolution like no other writer except perhaps Richard Dawkins. Gould along with Niles Eldredge proposed the controversial and widely misunderstood theory of punctuated equilibrium. Seema Singh describes it thus: ... which propounded that evolution takes place in rapid spurts of species differentiation, not in continuous transformations.

I wanted to expand on this.

More specifically, when Eldridge and Gould suggested that "evolution takes place in rapid spurts of species differentiation", they meant that morphological changes took place mostly during cladogenesis i.e. when a new species formed by splitting of from an older species. Evolution is a much broader term to includes all heritable changes in a population over time. These include changes in morphology (driven mostly by natural selection) and also changes taking place at the molecular level by accumulation of neutral mutations by random genetic drift. This latter process is also evolution and it does result in continuous transformation of populations although its effect is not seen as morphological changes.  I mention this because there is an interesting connection between this type of continuous evolution and species differentiation. Evolutionary biologists use the rates of accumulation of neutral mutations - which work out to be more or less constant when large enough time periods are considered - to establish the timing of species differentiation. One can compare the genetic difference between two related species and work out backwards how long it has been since they diverged from a common ancestor.

Coming back to punctuated equilibrium, how valid was Eldridge and Gould's claim that species during most of their lifetime did not show much morphological change - stasis they called it - and that such changes took place only during species splitting (these morphological changes are quite small. Punctuated Equilibrium did not propound large shifts in morphology. It is not a theory of saltation aka "hopeful monsters") . Was there something special about speciation i.e. the formation of a new species that initiated morphological change? Later on in his career Gould did admit that they got this one wrong. There was no evidence to validate the position that speciation imposed some kind of special conditions that resulted in morphological changes.

Instead, he admitted first in a paper in 1993 and later on in his last book The Structure of Evolutionary Theory that evolutionary biologist Douglas Futuyma had the right explanation, which was that when populations of a species are in contact with each other gene flow between them will disrupt any directional morphological changes that may have accumulated over a short time span in one population. Gene mixing prevents any one sub population evolving distinct characters. In the fossil record this is observed as either no morphological change i.e. stasis, or change which meanders without a trend. It is only when a population gets reproductively isolated that a particular trajectory of morphological change may get fixed in that population. So, speciation does not trigger morphological changes but reproductive isolation which is necessary for speciation plays a role in preserving change and giving it a permanence that shows up in the fossil record.

What about the other extreme case that new species may indeed form by a slow continuous morphological transformation of an older species (phyletic gradualism) and not through a pattern of stasis, sudden apparent change and species splitting. By a most delicious irony a case of phyletic gradualism was demonstrated by Stephen Gould's ex PhD student Anthony J. Arnold and his colleague William C. Parker at Florida State University. They used a database of Cenozoic formaminfera acquired from sediment cores drilled into the Gulf of Mexico sea bed to demonstrate slow morphological change in populations. Observing the foraminifera fossil record over the span of a few million years they showed through quantitative morphological analysis that enough change had accumulated to justify calling that population a new species.When Gould visited his former student and learned of this finding he admitted that this was a case of phyletic gradualism in contrast to his expected pattern of stasis and sudden change. He called forams an exception... but as they say.. biology is full of exceptions!

I got a first hand account of all this exiting research because Anthony Arnold sat on my PhD committee and William Parker was my PhD adviser. Anthony Arnold told me quite a few stories about Gould. He spoke with great respect about him. He told me that Gould gave his student's full attention when discussing their work but did not chit chat much. He had a fantastic work ethic - he never missed a deadline of his essay series published in Natural History magazine - even when suffering from mesothelioma ( a rare form of stomach cancer). He was generous to this students, often funding them from his essay writing earnings. There were times during his cancer treatment when he had lost a lot of weight. Students were bringing him chicken soup to keep his spirits and energy up..but Gould soldiered on.

When he died in May 2002 I emailed Anthony Arnold. We exchanged a few mails about his work. I mentioned what a tome his last book was and that Gould must have really put a lot of effort in polishing up his ideas. I thought of that book as the culmination of Gould's thinking on various topics on evolution. Anthony Arnold though had a completely different take on it. He told me that Gould was still struggling with many of the ideas on evolution that form the centerpiece of The Structure of Evolutionary Theory. There were many ideas he was thinking about. Punctuated Equilibrium, Species Selection, The Hierarchy of Natural Selection (inspired by an epic paper on that topic by Anthony Arnold and Kurt Fristrup).  He was still arguing with himself and refining them, but it is possible that a downturn in his health may have prompted him to finish up that book.

Arnold paraphrased a famous line: If only he had more time, his book would have been shorter.


  1. Superb. Thank you Suvrat for picking up the threads from my piece in Current Science and writing this post, it's both informative and personal. As journalists, very often we (are forced to) scratch the surface and move on! This post vindicates what I've been arguing recently that we need more practicing scientists to write.

  2. Thanks Seema. I agree wholeheartedly that more Indian scientists need to open up and engage with the public.