Rewinding History

Some of the most interesting history thought-experiments consider the question of the inevitability of important world events. Was the South destined to lose the US Civil war due to its inherent disadvantages, or could some strategic blunder have turned the tide? The question of contingent history has a parallel in biological evolution. The difference is that science is now beginning to give us the tools to draw actual conclusions about what would happen if we could “rewind” the clock of evolution and play it again. We can start to identify the contingent calf-paths in our ancestry, and distinguish them from the traits, like flying and vision, which have evolved separately multiple times different lineages. The similarity between  marsupials and placentals is commonly cited as strong evidence that not everything is by accident. However, the amplifying effects of the “rich-get-richer” is a hallmark of network behavior. Just as the choice, possibly based on minor considerations existing centuries ago, of whether a tiny settlement might be built on bank of the river or the other can dictate the location of a modern metropolis, small, accidental changes may get locked-in by evolution.

We now have the opportunity to watch history play out again, either by doing it ourselves and growing 20 years of bacterial generations, as in the Lenski lab, or by resurrecting ancient genes from 500 million years ago and inserting them into modern specimens. The picture that is forming from these experiments is, as in history, a mix or randomness and inevitability that shows the importance of individual mutation events that can “potentialize” or “actualize” a given adaptation. There is likely to be a crucial, revolutionary advance hit upon by evolution that, by itself, does not totally provide for the trait, but is close enough so that some among the population of its descendants are, under the right external conditions, strongly favored to have a large advantage when they perfect the trait. So the response to our question should be “how far back do you want to rewind?” 

Poor Power

That the Gettysburg Address is among the most famous speeches in the American consciousness is one of history’s great ironies. If you actually read the words, Lincoln discusses the powerlessness of words, and that no one will care about what said that day:

 “…we can not dedicate, we can not consecrate, we can not hallow this ground. The brave men, living and dead, who struggled here, have consecrated it, far above our poor power to add or detract. The world will little note, nor long remember what we say here, but it can never forget what they did here.”

Perhaps this is why he spoke for only 2 minutes, while others droned on for several hours at the same dedication. In any case, the role of an observer, who notes but does not alter the situation, can to my mind today as I was teaching physics lab. In my class, overwhelmingly pre-med students, 12 of 15 were female. This might seem surprising for subject matter that had been seen as the Provence of men, but I was not so surprised.  I just started reading The End of Men: And the Rise of Women by Hanna Rosin. She is aware that the purpose of her book is not to set forth an argument, but rather to mark a  momentous shift in the course of the human experience. For the first time since ever, females are overtaking their chromosomal mismatched counterparts. Rosin points out that the rise of automation has dealt a heavy blow to traditionally “male” occupations, like construction and manufacturing. When given a level playing field, where brawn is not an issue, women are thriving and men are getting left behind. At Nova Southeastern University, where I teach, about 70% of the student body is of the female persuasion, and nationally the figure is around 2/3. In this new connected world, where a machine (or third-world laborer) can do most taxing and menial tasks, the value of education has never been greater. Women are seeing the larger divergence in life- paths between unskilled workers and trained professionals and choosing their education levels accordingly.

Revenge of Discarded Ideas

The webcomic xkcd has many gems, but one my all-time favorites pokes fun at how teachers have a pechant for over-emphasizing the wrong-ness of a “misconception.” In an usually admirable but misguided effort to move students from a naive way of thinking, “overzealous” instructors salt the Earth so that no further thinking can occur in the “wrong” tracts. However, sometimes the most seemingly incorrect views reappear when least expected. One of the famous scientific controversies middle school biology students are taught regards the theory of Lamarckism, which essentially states that evolution occurs because offspring inherit changes that occurred to their ancestors. The classic example is of a giraffe, which is said to acquire a long neck from stretching for the leaves at the top of trees. According to Lamarck, this useful trait (long neck) is then inherited by its children. Ask any elementary school teacher about the “heritability of acquired characteristics” today, and you are overwhelming likely to hear stories involving mice getting their tails hacked off, but going on to give birth to normally-tailed offspring. Students get drilled into them the concept that only germ cells can carry heritable information, and that what happens to a organism during its lifetime has no bearing on the “book of life” it gifts to its offspring. But what if that book can have annotations? The growing field of epigenetics is showing almost daily that just a copy of the “instruction manual” is not enough to get through the business of living. Genes can be turned on or off, in way we are only beginning to fully appreciate. For example, all the cells in your body, whether nerve, muscle, lymphocyte or whatever, carry around a full copy of your DNA sequence. The assignment to become a certain cell type requires changes that “mark-up” the genes needed or not needed, depending on the jobs. This may be done with chemical tags; for example, adding a methyl group to a nucleotide base to change how its gene it encodes is expressed. We are finding that some changes, like the difference between worker bees as nurses or foragers, are reversible, or even heritable from your parents experiences.

While it may be important to replace naive conceptions of giraffes with more sophisticated ones, teachers often do a disservice to their students by “overselling” certain concepts. Because nature is (and must be) more complex than that.    

The Entropy of Replication

Even life has to obey the second law of thermodynamics, which states that the amount of Entropy, essentially, the degree of disorder, can only increase in a closed system. Increases in entropy in some region must be balanced by increases in other region, or else by the conversion of useful energy into “heat,” that is no longer able to do further work. Therefore, every “ordering” process, including the self-replication of an bacterium can be assigned a minimum amount of energy required for that process. Although the sun is constantly radiating energy down on Earth, collecting and using it is not a simple task. Life has found ways to economize and reproduce copies without consuming much more than the theoretical limit. 

Science History

The New York Times science section recently profiled the Royal Society, the “world’s oldest continuous scientific society.” I am very interested in the history of science, but I seem to perceive a dichotomous attitude eminating from scientists about their own story. One the one hand, it can be very illuminating to see how, and specifically, the order discoveries were made. Often, this is mirrored, consciously or not, by teachers whose lessons recapitulates this sequence. On the other hand, scientists might rather forget the wrong turns taken before reaching the currently accepted answer. Once you know the solution to the puzzle, why waste any more effort on incorrect guesses? There is, however, another possible reason. The natural sciences try to remove the human element, at least to the extent this is possible. Almost by definition, the laws of nature studied should be unaffected by the presence, or lack thereof, of humans to observe them. And they should certainly be immune to the vicissitudes of then-current events. However, as pointed out by the books The Age of Wonder, and The Clockwork Universe, show the interaction, both ways, of science and history. The Royal Society did more than anyone to promote its motto Nullius in Verba, in a world in thrall to received wisdom. Discoveries backed by the Society, like exotic island tribes and new planets, sparked a sense of amazement in the general population. Science, like everything, is subject to the whims of history. Chemist Antoine Lavoisier’s work was cut short by the guillotine. Texas might have celebrated the discovery of the Higgs Boson long ago, but for budget cuts.  When I had the opportunity to visit the British Museum, I was duly awed by the amazing collection of artifacts, but it is hard to doubt the importance of Empire, and associated colonialism, that allowed such a collection to exist.