Quick impressions of “Evolve: Eyes” on the History Channel

I recorded the TV show Evolve:Eyes, which aired on the History Channel last night, and I watched it today. Last night during the original airing, I was in LA watching the Dodgers with my family. I think my son was quite taken with professional baseball. This was not his first game (I had to make sure that for both kids, their first game was in Milwaukee, where mine was), but I don’t think my son remembers seeing the Brewers in Miller Park. So when we walked through the gate of Dodger Stadium, I saw the awe in his eyes, as he took in the stadium’s brightness, the impossibly green grass, and as we heard 40,000 fans cheer together. There is something to be said for appearance and spectacle, which can make even things like playing baseball games seem important.

This was the primary strength that I found in the History Channel show Evolve:Eyes; it looked really slick; it had its share of spectacle. There were fantastic graphics. Three dimensional eye figures exploding into component lens, cornea, and retina. The linear progression of eye evolution was re-told graphically, a few photoreceptors morphing into a deepening pit. Then a lens appeared, until the human eye had “evolved” right before my own eyes.

There were also dramatic film sequences of real scientists. There was a re-enactment of my friend (we were postdocs together in Chicago) Nate Dominy of UCSC doing his field research observing primates (I’m guessing they filmed Nate in Santa Cruz with binoculars and cut in footage of primates). There was footage of my friend Chris Kirk (haven’t seen him for a while, but we were grad students at Duke at the same time) pulling eye balls out of jars, complete with lab coat (most biologists I know don’t wear lab coats, unless they’re being filmed, or maybe if their pulling eyeballs out of a smelly formalin/ethanol solution). And there was footage of my colleague Alex Goodell collecting Polyorchus (a cnidarian) and shining LED lights on them to watch their behavior: green light, then blue, illuminating the tank and animal like neon lights in the dark. Scott Edwards, alone in an arid landscape, artistically filmed full-body and off-center, commented on how many times eyes evolved, my proverbial red herring, deciding to re-tell the take of a fellow Harvard-man, the late Ernst Mayr. Spectacle. Beautiful.

But all was not positive from my perspective. Namely, the show fell into the two most common traps that plague the understanding of evolution by the public. 1) Evolution is not adaptive story telling and 2) Evolution has not progressed in a direct line from simple to complex; evolution most certainly does not culminate with the human species. In nature, humans are no more special than bacteria. We are just another twig on the great tree of life (that was for Eisen).

Very little of this show was actually about evolution, and most of the “evolution” that was mentioned did not explain the actual science behind it (there were of course some excpetions). Instead, there was a lot of adaptive storytelling. Eagles evolved amazing vision to allow them to be better hunters. I don’t doubt this is true, but this show very often simply asserted and explained current function, with little mention of how evolution of those traits proceeded. Jellyfish try to escape UV/blue because it is damaging. Again, this may be true, but it was simply asserted in the show. Evolution was simply assumed, with little mention of how we actually have established that evolution works.


But the most egregious to me was how the narrative and graphics re-enforced the non-existent linear progression from jellyfish to humans. In fact, the graphics were a line, shown between stories, proceeding from 600 million years ago to present day primates. In this hypothetical line, first came the “jellyfish” (they actually showed a hydromedusan). The camera simulated the “primitive” jelly’s blurry vision, far inferior to our own, no mention of the cubomedusan’s highly complex eye. Next came the trilobites, whose calcite compound eyes are among the oldest fossil eyes. (To the show’s credit, they did mention that trilobites are not direct ancestors of living arthropods, a slight nod to “tree thinking”. Also, the Cambrian and trilobite animations were pretty cool. More spectacle.)


Then came the vertebrates. Not much mention of fish, instead we jump to dinosaurs. More flash here, tremendous spectacle, shining lasers on models of T. rex, the icon of charismatic species. Then the story moves up the ladder to early mammals, “primitive mammals” eeking out an existence, with only “black and white” vision, living in the shadow of dinosaurs. Then the great KT event knocks out rex and mammals can finally flourish. This next bit really got me. They compare human (and some other primates’) vision to that of early mammals, saying how great we are to be able to see red. What a shallow point of comparison, just to inflate the human ego, and maintain the march of progress up to humans! Why not compare to our eyes to stomatopods (mantis shrimps), who see circular polarized light, and have upwards of 12-chromatic compared to our tri-chromatic vision. Or even compare us to adult maggots (i.e. flies), who see polarized and UV light that we cannot detect. In my book, the evolutionary ladder of eyes proceeds up to mantis shrimp, not humans.



But perhaps I am being a bit too critical, expecting too much nuance from a show aimed to keep viewers from switching to, say, ESPN to see how the Dodgers are doing (they won by the way). Spectacle can be something to celebrate!

After the Dodger’s game last night, I could tell my son was inspired by spectacle, not by nuance. In fact, I doubt he got any nuances of the game. He was oblivious to strategic pitching changes; clueless about a rare call that gave the Dodgers an extra run in a tight game (the Giant's left fielder juggled the ball out of play, something I’ve never seen, after many years of watching baseball, e.g. I’ve seen in person a triple play, and Ricky Henderson’s record breaking stolen base). No, it wasn’t nuance that compelled my son to ask when he gets to start soccer, and if I can video record his games so we can watch them on TV. It was spectacle, fan screaming, light flashing, ice cream in a Dodger helmet spectacle.

So who am I to complain if somewhere, some kid is taken by the spectacle of eye evolution, as so vividly portrayed last night? Taken by the idea of shining lasers on T. rex, or neon LED’s on pulsating jellyfish in dark rooms? Maybe an African-American kid saw Scott Edwards on TV last night, and dreamed a dream of studying evolution. Maybe the child of an anti-evolutionist now has some questions.

There is a place for spectacle. If spectacle can inspire, nuance can come later.

Choose your own descent

I was interested to see that over at The Tree of Life Jonathan Eisen discussed a few different metaphors for common descent, which include:

The tree of life
The coral of life
The watershed of life
Blood vessels of life
Lungs of life
Shrub of life


I think metaphors are useful for teaching the idea of common descent and tree thinking, and so I try to think of new metaphors from time to time, since I teach a course on Macroevolution and also talk a lot about phylogenies in an Invertebrate Zoology course.

One that I think is really powerful, is found in Richard Dawkins' book Ancestor's Tale. The idea there is to reverse time in common descent, and imagine humans walking on a path to join our ancestors. First chimps join the band, later other apes, then other primates, other mammals, etc. This analogy is good for understanding the history of a particular entity, like the human species. However, since it has a specific starting point, it tends to re-enforce the way people conceive of evolution as a linear series of events. This is true if we have one specific endpoint in mind (like humans), but evolution does not have one specific endpoint.


So, this morning, this was going around in my head, and a new metaphor sprung into my brain: A choose your own adventure book. These books have a section of the story, and then the reader must choose between two (or more) different paths, each with a different outcome to the story.


Congratulations, your character has just achieved bilateral symmetry! If you would like to proceed down the path of protostomy, go to page 150. If you would like to proceed down the path of deuterostomy, go to page 376. It might be fun to write an actual evolution book this way!

Textbook linear evolution

I presented my ideas on the limitations of linear evolution, versus tree thinking, in a presentation to a Department of Ecology and Evolution, and got an interesting comment. A colleague challenged my statement that the "morphological series" of eyes (at the time I presented a specific figure from Salvini-Plawen and Mayr on gastropod eyes, which will be the subject of a future post) was presented as a model of evolution. The commenter was actually was a colleague of Mayr at the time, and the commenter stated that Mayr and people at that time weren't thinking of this as a model for how evolution actually proceeded.

Well I am very grateful for this comment, because others may be thinking the same thing - that the linear series of eyes are not meant to represent a model of evolution per se. In fact, I believe this may be true, at least for the time when it was authored. However, as I will explain below, people do currently use eye series as models for how eyes actually did evolve.

So, why do I believe that there initially could have been different intent? Well, all these morphological series do is to test an ancillary assumption of the hypothesis that natural selection drove the origin of complex eyes. If natural selection did and could drive eye evolution, an ancillary assumption is that a series of intermediate steps exists between a simple and complex eye. This was Darwin's strategy in Origin - to point out support for this ancillary assumption by highlighting eyes of living animals at many different levels of complexity. Salvini-Plawen and Mayr refined Darwin's idea by providing such series in closely related groups of animals. True, a test of an ancillary assumption of natural selection may not have been intended as a model of how evolution actually proceeded. Incidentally, another ancillary assumption that natural selection produced complex eyes is that there was enough time for the process to work. Nilsson and Pelger tested this with a morphological model, and several calculations, but that is a topic for another post. Perhaps, Salvini-Plawen and Mayr were not equating the eyes of living animal eyes with ancestral states of extinct animal eyes (although this is not uncommon). Certainly testing an ancillary assumption is good science, but it also may not represent the proposal of an actual model.
Nevertheless, these morphological series are now taken as models of how evolution actually proceeded. For example, I just came across such a series in the textbook I use for my Macroevolution course. The text is Ridley's Evolution, 3rd Edition. Note that the caption begins, "Stages in the evolution of the eye".

At this point, I need to re-iterate, there is value to these series, in testing an ancillary assumption. But it could be dangerous to equate the eyes of living species, with those of species in a progessive series of evolution, from simple to complex eye. Furthermore, these series ignore the origins of variation. For example, the caption states "An eye is protected by adding a transparent cover of skin and part of the cellular fluid has differentiated into a lens." How does an eye add a transparent cover? Where does the variation come from? How does fluid differentiate into a lens?

Studying natural selection at the level of morphology alone is silent on these points, because it assumes variation is abundant, and that variation is then left to be anonymous. But exciting times are upon us, because we are know beginning to uncover the molecular basis for phenotypic changes. There is no designer - it is all mutation and natural selection - but by looking at the molecules, we can gain a new level of detail in our understanding of how complex traits evolve.

For one example, where we've gone beyond a morphological series, see a previous post of mine on the evolutionary origin of a cephalopod lens....

Linear Thinking in Ostracod Eye Evolution

People often ask me how I came to study something as obscure as ostracod crustaceans. The answer is a funny story.

The spring/summer before moving to Duke University to start working for my PhD, I was thinking about what I would do for my thesis. At that time, I was already interested in testing comparative methods aimed at estimating what extinct species might have been like, the methods are called "ancestral state reconstruction". Well, one part of the project was to work on a phylogeny of viruses that was evolved in the lab. The actual ancestors were preserved in the refrigerator, so I could estimate these ancestors using the existing methodologies.

In addition to the virus study, I wanted to do a similar exercise with a group of organisms that have a good fossil record, and compare estimated ancestors to the fossil record. So, I wrote my advisor-to-be, to ask if he could recommend a group with a good fossil record. The email came back with the title "Ostrocads are it!!". Cliff had accidentally inverted the o and the a in "ostracods".

Once I figured out what is an ostrocad, the first paper I came across was by Andrew Parker, who would later help me in many ways by email, as well as in person when I collected ostracods in Australia. Here is a news story about us, with a photo taken near Sydney.

Andrew's paper was entitled "Discovery of functional iridescence and its coevolution with eyes in the phylogeny of Ostracoda (Crustacea)". In it, he suggested "The myodocopid lateral eye probably evolved at a similar point in time as iridescence, possibly to detect iridescence. The graduations by which the ostracod compound eye has developed are suggested. These findings challenge current theories which demand a single evolution of the compound eye."

These provocative statements would lead to the bulk of my dissertation, which tested Andrew's ideas using molecular phylogenetics and ancestral state reconstruction.

The "graduations" Andrew suggests are illustrated in his figure 5. His caption begins "Possible means of derivation of the myodocopid compound eye."



This is a perfect example of linear thinking, versus tree thinking. Laid out are 3 living species of myodocopid ostracods; all from the same family. These are used to represent a linear, graduated series from a simple eye in Azygocypridina, to a complex compound eye in Macrocypridina.

"Lineage"

It is interesting that evolutionists quite often use the term "lineage" to refer to a clade. I feel I've seen this in many contexts. Gene families may be called a lineage. A clade of species may also be called a lineage.

What is linear about these groups of biological entities? I think almost nothing. A clade of genes or species contains a common ancestor. A line can be drawn from that ancestor to any of the terminals. However, the decision of which line to draw is arbitrary, unless a single gene or species is all that is of interest in the clade.

Clades are not lineages, they are clades. Clades are branching diagrams without any inherent linearity. I think referring to clades as lineages provides yet another example of how linear thinking is embedded in the way people see the world. "Tree thinking" is a skill central to understanding biology. But to achieve this skill requires people to overcome innumerable difficulties. Some, such as referring to clades as lineages, seem subtle, but nevertheless probably have an effect on our ability to see biology as a collection of branching processes.