Complex Arthropod Eyes Found in Early Cambrian
Complex eyes with modern optics from an unknown arthropod, more complex than trilobite eyes, have been discovered in early Cambrian strata from southern Australia. The exquisitely-preserved imprints of the eyes in shale were reported by Lee et al. in Nature.1 The abstract started by quoting Darwin and affirming evolution, but then revealed evidence that complex eyes go further back in the fossil record than previously thought possible:
Despite the status of the eye as an “organ of extreme perfection”, theory suggests that complex eyes can evolve very rapidly. The fossil record has, until now, been inadequate in providing insight into the early evolution of eyes during the initial radiation of many animal groups known as the Cambrian explosion. This is surprising because Cambrian Burgess-Shale-type deposits are replete with exquisitely preserved animals, especially arthropods, that possess eyes. However, with the exception of biomineralized trilobite eyes, virtually nothing is known about the details of their optical design. Here we report exceptionally preserved fossil eyes from the Early Cambrian (~515 million years ago) Emu Bay Shale of South Australia, revealing that some of the earliest arthropods possessed highly advanced compound eyes, each with over 3,000 large ommatidial lenses and a specialized ‘bright zone’. These are the oldest non-biomineralized eyes known in such detail, with preservation quality exceeding that found in the Burgess Shale and Chengjiang deposits. Non-biomineralized eyes of similar complexity are otherwise unknown until about 85 million years later. The arrangement and size of the lenses indicate that these eyes belonged to an active predator that was capable of seeing in low light. The eyes are more complex than those known from contemporaneous trilobites and are as advanced as those of many living forms. They provide further evidence that the Cambrian explosion involved rapid innovation in fine-scale anatomy as well as gross morphology, and are consistent with the concept that the development of advanced vision helped to drive this great evolutionary event.
How the immediate appearance of a complex trait like vision could “drive” an evolutionary event seems strange, since the eyes were already there during the event. No transitional eyes simpler than this were reported. Though the authors gave lip service to evolution, all the evidence pointed to more complexity and adaptive perfection than was thought possible for animals this early. Here are some details about these compound eyes:
- A side-by-side comparison of the fossil imprint with a living insect eye shows virtually no difference in complexity.
- The fossil eye was compared by the authors in complexity to a dragonfly eye: “The ratio of lens diameters in the bright zone to lens diameters in the margin (~2.5:1) exceeds that found in other Cambrian arthropods (trilobites and cambropachycopids) and is comparable to that in many modern taxa such as dragonflies,” they said.
- “The extremely regular arrangement of lenses seen here exceeds even that in certain modern taxa, such as the horseshoe crab,” the authors said.
- The eyes apparently gave their owners binocular vision: “This bilaterally symmetrical arrangement generates binocular vision,” they suggested, though proof will require discovery of articulated remains.
- The eyes would have been good for a fast predator: “Acute forward vision and lower-resolution peripheral vision are typical of predators that require excellent frontal vision for estimating distance and detecting prey against complex backgrounds; they are also typical of fast-moving organisms in which acute peripheral vision is precluded by a high retinal angular velocity.” That being the case, the animals would have had many other advanced features in addition to eyes. “The complexity and large size of the Emu Bay Shale eyes strongly indicate that they belong to an active arthropod, probably a large predator.” These eyes, however, were smaller than those of Anomalocaris.
- This is a game-changer: “The arrangement and size gradient of lenses creates a distinct ‘bright zone’ (also called the acute zone or fovea), where the visual field is sampled with higher light sensitivity (due to large ommatidia) and possibly a higher acuity (due to what seems to be a more parallel orientation of ommatidia),” they said. “Such visual specializations, characteristic of many modern taxa, are otherwise unknown in the Early Cambrian.”
The animal type is not known, since articulated remains have not yet been found. The imprints may be from shed corneas, they said. Their graphs show that these eyes exceed most other arthropod eyes of the Cambrian in complexity, even among those of the Ordovician.
In their concluding paragraph, they affirmed use of the phrase “Cambrian explosion” as a real event. They could offer no explanation for the evolution of these eyes, nor did they put forward any transitional forms. They merely assumed evolution occurred quickly somehow:
The evolution of powerful vision is one of the most important correlates of the Cambrian explosion and has been proposed as a trigger for this event. However, although the overall shapes of eyes are known for many Cambrian organisms, intricate details of the visual surface are known only for trilobites and the tiny stem-crustacean cambropachycopids, which have bizarre, proportionately huge and medially fused compound eyes. In addition, indistinct ommatidia are preserved in a few Chengjiang fossils, including the non-biomineralized arthropods Isoxys and Cindarella. Isoxys inhabited both dim and bright pelagic environments whereas Cindarella probably inhabited a bright benthos. The specimens described here represent the first microanatomical evidence confirming the view that highly developed vision in the Early Cambrian was not restricted to trilobites. Furthermore, in possessing more and larger lenses, plus a distinct bright zone, they are substantially more complex than contemporaneous trilobite eyes, which are often assumed to be among the most powerful visual organs of their time. The new fossils reveal that some of the earliest arthropods had already acquired visual systems similar to those of living forms, underscoring the speed and magnitude of the evolutionary innovation that occurred during the Cambrian explosion.
Live Science posted a summary of this finding, showing how the visual acuity of the animal bearing these eyes was superior to that of trilobites and indistinguishable from the acuity of the dragonfly. Though the dragonfly has eight times the number of individual ommatidia, the Cambrian eyes surpassed those of other fossil arthropods dated 40 million years later. Live Science’s article also quoted the authors’ confirmation of the Cambrian explosion: “The new fossils reveal that some of the earliest arthropods had already acquired visual systems similar to those of living forms, underscoring the speed and magnitude of the evolutionary innovation that occured during the Cambrian Explosion.”
PhysOrg featured a video showing the fossil in 3-D and comparing it to other arthropod eyes. The article tried valiantly to save evolution from this new evidence:
Their discovery reveals that some of the earliest animals possessed very powerful vision; similar eyes are found in many living insects, such as robber flies. Sharp vision must therefore have evolved very rapidly, soon after the first predators appeared during the 'Cambrian Explosion' of life that began around 540 million years ago.
Given the tremendous adaptive advantage conferred by sharp vision for avoiding predators and locating food and shelter, there must have been tremendous evolutionary pressure to elaborate and refine visual organs.
Science Daily said the fossils look like “squashed eyes of a recently swatted fly.” How could evolution explain this? The headline put forth its thesis: “New Fossils Demonstrate That Powerful Eyes Evolved in a Twinkling.” Stuff happens, and it happens quickly.
1. Lee, Jago et al., “Modern optics in exceptionally preserved eyes of Early Cambrian arthropods from Australia,” Nature 474 (30 June 2011), pp. 583–584, doi:10.1038/474583a.
OK, skeptics, face the facts. Complex eyes, “organs of extreme perfection,” are already there in the early Cambrian. Where are the transitions? Trilobite eyes were already astonishing, and now these exceed them in complexity, and appear earlier than the best examples of complex trilobite eyes! They are comparable to modern insect eyes. You cannot call these a trigger of the Cambrian explosion–what nonsense! That’s like saying, “Revolvers appeared out of nowhere, and triggered the Civil War.” The eyes were already there, fully formed, fully operational, even within the incestuous dating scheme of the evolutionists. Arthropods are exquisitely complex animals, crowned with glorious eyes as well as many other senses and systems that allow for rapid motility and function. Who needs a Cambrian rabbit?
You can go to the Amazon reviews of the DVD Darwin's Dilemma and see Donald Prothero self-righteously rant against ignorant creationists, announcing with his professorial authority that the Cambrian explosion was no explosion but was a long slow fuse. Hold this paper up to his face. Here a team of Darwin-worshiping scientists with no love for intelligent design, publishing in the world’s leading science journal Nature (also no friend of intelligent design) called it an explosion five times in their paper. They discovered organs of extreme perfection in the early Cambrian with no transitions, only offering in defense of Darwin the vain hope that eyes might evolve rapidly, tossing that hot potato to Nilsson and Pelger (whose computer model was amply debunked long ago–see ENV 2006, ENV 2007, ENV 2011). Science is supposed to be factive, not fictive.
The Cambrian explosion is affirmed; complexity appears suddenly without transitions; Darwinism is falsified; the inference to the best explanation is intelligent design. Let the world know.