There have been living creatures on Earth for about four billion years, but most of that time they were blind. Most of that time, also, they were very simple (single cell animals, sponges, and soft-bodied animals). The famous Cambrian explosion was the sudden boom in animal diversity that happened between 543 and 538 million years ago. It is when teeth and armor appeared. It is also when eyes appeared. It is easy for us to imagine the drama of, say, the destruction of the dinosaurs 65 million years ago, but according to Andrew Parker the Cambrian explosion is "the most dramatic event in the history of life." Other dramatic events have their explanations (an asteroid wiping out the dinosaurs, for instance), but there has not been a satisfactory explanation of the Cambrian boom. Until now, according to Parker, and he has come up with it. _In the Blink of an Eye_ (Perseus Publishing) is a convincing explanation that he first announced seven years ago: the Cambrian explosion was caused by the evolution of vision.
What happened in the explosion is that animals acquired armor, hard body parts, and a huge variety of different shapes. Parker explains that the shapes and armor came along because eyes came along. In the blind pre-Cambrian world, creatures took in sensation by smell / taste, sound, or touch. It did not matter what the creatures looked like, because no other creature could see them. It didn't matter if creatures had no armor, because predators weren't chasing them. Creatures scavenged upon dead animals, but did not need claws or jaws to catch those; catching prey was unlikely for a creature that was blind, so predation was not the rule. And then there was light! Parker thinks that a soft-bodied ancestor of the trilobite was the first creature to get a light sensitive patch that eventually differentiated into different units of an eye. The trilobite that could gradually see better could gradually become a better predator. Not only does vision power a diversity of the trilobite itself, into such skills as agility and efficient use of muscular propulsion, it powers changes in prey. In the dark, an animal has no need to care what it looks like. Pursued by creatures that can see, an animal has many avenues of change that it might follow, like making camouflage, developing its own armor, swimming faster, growing bigger, or gaining its own eyesight. And then the predators can become modified to overcome those tactics, and the familiar evolutionary battle is enjoined in earnest. Vision started diversity, and has powered it ever since.
Parker's book is a rich account of how he came to these conclusions, with a wide-ranging gathering of supportive evidence. He writes clearly, and with a witty understatement. When, for example, he describes examining seed-shrimps and dissecting them under the microscope, he says, "The seed-shrimps tend to roll around and fall in exactly the positions that are not required of them." Any scientific theory is open to question, and surely the very simplicity of Parker's explanation will make it a target for other theorizers with new data. Right now, though, in considering the Cambrian explosion, the Light Switch Theory is the way to see things.
on May 27, 2004
No thinking person can deny that the presence of light in the environment can be an important selective pressure. Indeed, as Parker argues, it may have been one of the most important influences on the evolution of locomoting organisms since locomotion began. In a very small nutshell, his thesis that adaptation to light, especially the development of sensory mechanisms to take advantage of light in the environment, is reasonably easy to believe.
I am a student of perception and I wanted to be persuaded by Parker's argument, but the book itself is not well done. There is a ridiculous attempt to generate suspense about the conclusion Parker ultimately draws...a conclusion that is basically no surprise if you read the dust jacket. The language is often stilted and pedantic, to my eye, making me wonder if this isn't a warmed-over dissertation recast as pop science.
The most irritating element of the book, however, is the routine citation of items from the research literature...but with no reference list to which to turn for the full citation. Even decent popular science books have at least a few sources for further reading, and notes of some sort for the particulars of research cited. Parker's book has neither.
The book has some value (hence the three stars) for pointing out a variety of interesting elements of invertebrate visual system evolution, but does not help at all if one wants to follow up such threads.
Okay, I'm not a paleontologist and not a biologist, so maybe I'm talking through my hat. Simon Conway Morris, however, IS an eminent paleontologist. If you want a truly informed review of Parker's book, see Morris's review in American Scientist, July/Aug 2003, p. 365 ff. Quoting very briefly: "The jaunty style becomes increasingly irritating, and the claims for scientific originality increasingly questionable."
In this illuminating [sorry!] study, Parker contends that light is the driving force behind evolutionary change. Light, he argues, is the most prevailing environmental element. Crossing biology, geology, ecology and physics with a bridge of optics, he shows how many body structures have varied due to light's availability and intensity. Most important to the reader, is his contention that when life developed a greater sensitivity to light, evolution was given a significant boost. We call the time of that "boost" the Cambrian Explosion. According to Parker, the mechanism driving the boost was the evolution of the eye. The wide diversity exhibited by evolution's abrupt advances around 550 million years ago produced creatures whose descendants are cats, bears, birds, and you. Parker provides a wealth of background material in developing his thesis. The forces of plate tectonics, the way light is absorbed, reflected, bent, and even biologically generated are all presented. He shows the relevance of each aspect in a slowly and carefully built concept.
Parker presents his theme with verve. "Let there be images!" is a concluding example. New ideas in science tend to use a forceful approach. Since he's laid a firm Darwinian foundation for this exclamation, perhaps his enthusiasm is warranted. He explains much about early life, the nature of light and how animals have adapted body plans to use light effectively. Parker shows how new research tools can analyse fossils to reveal the past wasn't the soft, dull, colourless world often portrayed. Some of the tricks developed by Nature millions of years ago weren't duplicated by human technology until very recently. Light, he explains, was both an attractant and a repellent in the shallow seas of early oceans.
The mortar binding the facets of Parker's idea is predation. Both eaters and eaten needed to detect each other to survive. In parallel with the eye, bodies changed to avoid detection and deflect biting mouths. Survival in evolutionary terms, he reminds us, means more than eating or avoiding being a meal. Vision enhanced the process of sexual selection, with the new body forms exhibiting colours to attract mates. These and other factors combine to provide what Parker calls his "Light Switch" view of the Cambrian period. As a foundation for his hypothesis, Parker joins the ranks of Eldredge and Gould's "punk-eek" [punctuated equilibrium] cabal of evolutionary biologists. This step is taken to grant eye evolution a rapid pace in line with the many changes the Cambrian Explosion seems to evidence. That's unfortunate, since it isn't necessary and he refutes the idea many times in citing his own evidence. A species span of
120 million years without a bump is equilibrium indeed!
Parker's ebullient prose is supplemented by excellent line drawings and photographs. These provide both background and examples of his points. His style, while ardent, is a bit rambling, although this can be forgiven in a book covering so many aspects of evolution's path. What cannot be forgiven is the lack of any bibliography or notes. This lack is outrageous and insults the reader. Although many researchers are presented, few titles grace the pages, leaving the reader with the task of seeking further information or confirmation almost from scratch. The publisher has no excuse for allowing this lack. Read this book, reflect on Parker's ideas, and remember there are other proposals for the cause of the Cambrian Explosion equally or better presented. [stephen a. haines - Ottawa, Canada]
on September 3, 2004
In his book, In the Blink of an Eye, Australian biologist Andrew Parker offers a new perspective on the so-called Cambrian explosion. Using a vast repertoire of supporting data from subjects as diverse as economics and optics, he builds a very cogent case for the introduction of a new biological sense that changed all the rules for a then very ancient living world. Although it gets a little bogged down in the discussion of shrimp, their light production and vision, the overall text is full of interesting illustrations of his thesis and conclusions to be drawn from them.
To begin with, the author looks at what life is very probably to have been like during the Dark Ages of the Precambrian. Professor Parker approaches the subject by suggesting that internal and external body plans have had different evolutionary histories and rates, and that the basics of internal body plan-those aspects that are not preserved well if at all in the fossil record-had already arisen during that early period of life's existence. Those changes in structure that would require the greatest effort and the most time, were so firmly set by the end of the period that while some phyla have dropped out, no new ones have been created. Focusing on the newer interpretations of the Ediacaran and Burgess life forms, the author believes that most of the external body plans were worm-like because there were few forces for the development of others. While the internal structures were distinct to accommodate different niches, the externals remained unchanged.
Everyone agrees that the efflorescence of external forms, particularly those with hard parts, after the Cambrian was both prolific and amazing. For Darwin, who had no access to information on Precambrian life or genetics, it posed a major challenge to his theory of evolution. It appeared as if life came diverse and fully formed out of nowhere and began to proliferate exponentially from its first appearance. What everyone hasn't agreed on heretofore is the reason for that sudden burgeoning of body forms.
Professor Parker takes the reader through various arguments that illustrate his thesis, namely that prior to the Cambrian it was essentially a blind world. He suggests that prior to that point in time light could be sensed, but visual images were not possible, that neither the "hardware" nor the "software" for actual vision existed. Without that sense predation, while it existed, was almost accidental. Once the creation and interpretation of images was possible, vision drove the evolution of both predator and prey in an escalating manner.
Superb reconstruction of an unusual time in life's history.
on August 31, 2005
This book is worth the time to read, even though early on, the style is as crisp as it should be. But once it gets going, this book is a treasure trove of examples of evoluntionary development, of environmental pressures and opportunities, and of the cumulative effects of natural selection on the development/evolution of light sensitive organs and eyes. It's a great counter to the ID, Intellegent Design/Creationist view that complex things/organs can't have evolved. The complexity of the eye has long been used by ID/Creastionsits as an example of an organ that would fall apart if any part were missing. Well this book shows very well the myriad of evolutionary solutions to the environmental pressure of the presence of light, from very primitive to very complex organs of vision. Mr. Parker shows the great range of ways, the multiple evolutionary paths of light sensing organs, some with lens, some without, some with an iris, some without, some with a single eye, some with multiple eyes. It should be mandatory reading (along with Dawkins' The Blind Watchmaker) for every member of the Kansas Board of Education and President Bush, who give up on exploring and understanding nature if it's complex, throw up their hands and say, "It's too complex. It must be from Intelligent Design." This is a very good exploration of some of that complexity in a naturalistic framework, i.e. a scientific framework.
on November 19, 2004
Parker's book was extremely interesting. As a geologist, I was delighted to find a book that was not completely bogged down with scientific terminology, so that I could pass this book on to my friends and family and share my interest. For someone who is not a geologist or biologist, a few of the terms may be a bit heavy. However, I believe for any science, paleontology or geology geek, this book is a must-read. The exploration of the Cambrian life forms is fascinating, the chapter on eyes alone is amazingly informative and very interesting. The reader will be swept away by Parker's enthusiasm and honesty. Especially enjoyable were his description of the male seed shrimp's attempts to court a female, and the descriptions of the predators and prey of the Cambrian. I have become enamored of Trilobites after reading this book, creatures I had previously not given a lot of thought.
on July 6, 2004
This book's theory is attractive enough that many experts ought to feel embarrassed that they didn't propose it earlier. It's not so much that people looking at the Cambrian explosion should have seen the evidence pointing to this theory - the book tends to indicate that some important pieces of evidence were only found in the last decade or so. What puzzles me is why nobody modelled the effects of the evolution of eyesight well enough to decide to go looking for the results in the fossil record. This makes me wonder whether a lot of experts are still uncomfortable with the punctuated equilibrium model of evolution.
But the book's style leaves much to be desired. It often goes off on irrelevant tangents. The absence of references to scientific literature is disappointing. I'm annoyed by the way he presents numbers such as "543 million years ago" with little indication of how accurately they are known.
on October 1, 2007
Other reviewers have mentioned Andrew Parker's proclivity in 'In the Blink of an Eye' to digress, to present his thesis as more revolutionary & unique than it actually is, & to fall into a 'gee whiz' style from time to time, & I will merely second those critiques, while agreeing with previous reviewers that Parker's book is nevertheless an entertaining & surprisingly broadly informative read.
But my primary criticism of Parker's book is his failure to construct a solid logical argument for his thesis, which is that the evolution of vision was THE cause of the Cambrian Explosion ('CE'). Parker tends to zigzag through his chapters, & upon reaching the end, claim that he has formulated a logically-sequenced argument, which he rarely has.
Few paleontologists, I think, would disagree with the idea that the development of vision (as distinct from mere light sensitivity) gave an enormous acceleration to Early Cambrian evolutionary rates, but Parker wants more than mere primum inter pares for vision, he wants it to have sole credit for the Explosion. To quote one reviewer: "What happened in the explosion is that animals acquired armor, hard body parts, and a huge variety of different shapes. Parker explains that the shapes and armor came along because eyes came along."
Yes, that's precisely Parker's explanation, but his argument leaves a skeptical reader not entirely convinced. At one point, Parker states (paraphrasing) that one must separate the CE itself (i.e., the evolution of fossilizable hard parts made of calcite) from the Cause of the CE. Stating it doesn't necessarily make it so. Sometimes an events IS the same thing as its cause.
Parker spends considerable time making the case that trilobites were the first creatures to develop vision. By Parker's own, slightly buried, report, this first lens that made vision possible was a calcite lens. I.e., it was either literally or virtually a modified bit of calcite body armor. If a bit of modified armor came first & made vision possible, how can one claim that "...armor came along because eyes came along."?
I don't want to argue that the evolution of vision wasn't crucial, merely that it's more reasonable to view it as 'primum inter pares', 'first among equals'. There's just too many evolutions of 'firsts' happening in the CE: first calcite secretion by multiple phyla, first eyes with considerable degrees of vision in multiple phyla, and several new body plans. It's probably more realistic to view these all as giving important positive feedback to each other, instead of crediting one as being the sole source of all the changes.
On this account, I think Parker's book would have been improved by a consideration of how & why so many different phyla evolved both calcite body coverings & vision so nearly simultaneously. The problem, to the best of my knowledge, is that we're still pretty much stumped by this one. Perhaps it's a useful place in earth history to postulate the incorporation, by several phyla, of bacterial DNA coded for calcite secretion, a la Lynn Margulis.
It makes no sense to somehow imply that the evolution of vision by trilobites somehow produces the evolution of vision in trilobite prey species. Evolution doesn't work that way, though that's the impression Parker just sorta leaves hanging out there.
Parker, like Dawkins before him, cites Nilson & Pelger's theoretical calculations of the rapidity--in geological time terms--with which "eyespots" can evolve into camera-type eyes. Perhaps a fruitful field for Parker to consider than would have been why then did vision not evolve prior to the CE? 99+% of all animal lenses through geologic history have been made of organic materials rather than calcite. Why then did lenses not evolve in multicellular life prior to the evolution of calcite secretion & hence the first calcite lens?
But again, the final line here is that Parker's book is an enjoyable & worthwhile read, even if it ultimately fails to marshall a complete & compelling argument in support of its thesis.
on January 23, 2014
This book makes an argument that was -- to me at least -- interesting and new. So from an intellectual interest perspective, I think that this book should be maybe 4 stars.
However, there's something strangely off about the writing. Parker inserts himself too much into the narrative, talking about what research he did, or which fossils he was looking at when some idea came to him. I'm frankly not that interested in his personal journey as a scientist; I'm interested in the ideas he is trying to convey.
Second, and more importantly, Parker takes a very strange hide-the-ball approach to the subject matter more appropriate to a mystery novel than a scientific book. Instead of telling us up front the argument he is making, he leads us through a tedious array of seemingly unrelated facts, only to tie them together at the very end of the book. So for most of the book, you will be thinking to yourself, "why is he going on about this? Is it central to the argument or is he going off on a tangent? I can't tell because I don't know what argument he's making." The end of the book is really worth reading, but unfortunately by the time you get there, you're too frustrated really to appreciate it. If you decide to read this book, you should definitely read the last couple of chapters first, then go back to the beginning. Honest.
So, bottom line is 4 stars for the ideas, but 2 star for the execution, resulting in a total of three stars.
Biologist Andrew Parker's "In the Blink of an Eye", is a spirited, provocative statement of his "Light Switch" theory accounting for the dramatic burst in the evolution of metazoans (multicellular animal life) at the dawn of the Cambrian Period of the Paleozoic Era, approximately 543 million years ago. He makes a very persuasive case that it was the evolution of eyesight in metazoans which triggered a rapid adaptive radiation of metazoans - though confined mostly - to arthropods (Living representatives include shrimp, crabs, lobsters, spiders, and insects, to name but a few.) as seen most impressively in the celebrated "Burgess Shale" fauna from approximately 515 million years ago.
Parker opens the book with a discussion of the Cambrian explosion and the nature of fossilization itself. Next he turns to the physics of light, and discusses how living animals use light not only for nourishment, but also as a means of defense, including - but not exclusively - mimicry to avoid detection by potential predators and prey. He also describes how sight has been lost by cave-dwelling animals, and the evolution of bioluminesence in deep sea creatures. Surprisingly, this leads next to exploring the possibility that Cambrian creatures were colorful, dressed in vibrant hues of many colors, which were quite visible in the shallow seas of the Burgess Shale fauna. The final chapters describe the evolution of sight in metazoans, and Parker alleges that a primitive ancestral trilobite has been discoverd in the uppermost occurrence of the Ediacaran (latest Precambrian) fauna with a pair of crude eyes. So why was sight necessary? Parker states that it arose as the direct consequence of some animals becoming active predators - the earliest trilobites - and this, in turn, triggered an evolutionary arms race in the development of body armor to defend from predation; which we see in the fossil record as the "Cambrian explosion".
Parker has made an elegant, persuasive case on behalf of his "Light Switch" theory to account for the Cambrian explosion. It is the most consistently logical explanation I have come across, supported amply by the evidence he has presented in this book. However, like another reviewer, I wish he had offered a bibliography citing those he has mentioned in support of his theory. It's a major oversight of both Parker and his publisher, and one which lessens the overall significance of the book and the compelling ideas presented within it. Still, I recommend this book to anyone interested in paleobiology - or in general, with evolution - especially those fascinated with the Cambrian explosion. Much to his credit, Parker has written a compelling tome which comes close to the literary eloquence attained by the likes of Stephen Jay Gould, Ernst Mayr and George Gaylord Simpson.