Biological Reasons Young-Earth Creationists’ Worldwide Flood Never Happened

Christians who call themselves creationists believe that a creator formed the universe, Earth, and its life, but beliefs about creation and evolution exist along a considerable spectrum.¹ Among the landscape of modern evangelical Christianity, many contemporary young-Earth creationists (YECs) have a narrow view of what constitutes “biblical” creationism.

Using well-established biological concepts and observations of living animals as well as in fossils of both plants and animals in the geologic column of sedimentary rocks, I will address concerns with this narrow view. I demonstrate that this view is misguided, that a worldwide Noah’s flood never happened about 4,350 years ago, and that Earth is much older than 6,000 years. This approach complements my earlier Skeptical Inquirer article, “Twenty-One Reasons Noah’s Worldwide Flood Never Happened” (March/April 2018), which focused on geological evidence.

Most young-Earth creationists believe that the sediments deposited by this flood were deposited over Earth’s globe and constitute a large portion of the geologic record beginning in the Cambrian Period in the Paleozoic Era to at least the end of the Cretaceous Period in the Mesozoic Era. They believe that all sedimentary rocks younger than this time from the Paleocene to the present (Holocene at the top of the time scale) were deposited after the flood (Hill et al. 2016). In the time scale shown in Figure 1, 6,000 years would hardly be the thickness of a sharp pencil line at the very top of the image. Therefore, the YECs condense the extent of animal and plant generations to an extremely tiny fraction of the length of this image. As I demonstrate, such a belief requires abandoning large portions of scientific consensus and common sense, but a recent Gallup poll² of the adult population in the United States indicates that nearly half of the people in this country (46 percent) believe what young-Earth creationists claim is the literal biblical time frame. (A more recent Gallup poll³ indicates that 38 percent of the adult population believes that humans were created by God in their present form but that a very young age for the origin of Earth is roughly 10,000 years.) However, in this article it is assumed that the very long ages indicated in Figure 1 are valid.

Much has been written about geological failings of so-called flood geology (Hill et al. 2016). Here I will focus instead on some observations of organic life and how their characteristics, ecology, and distribution raise far from trivial problems for the YEC understanding of a global flood.

Animals on Noah’s Ark

Regarding the origins and maintenance of biological diversity, young-Earth creationists also believe that the animals that are seen today were brought to Noah’s ark in pairs (or in septets for clean animals, per Genesis 7:2–3) and the pairs eventually evolved to form different species. That is, not all of today’s species (more than five million and perhaps as many as fifty million) were placed on the ark but only representatives of kinds or baramins.⁴ (A baramin is a badly coined word combining the Hebrew words bara [created] and min [kind]; minbaru is closer to the Hebrew.) Baramins (when referring to animals) are approximately equivalent to the taxonomic category of families of animals. For example, a pair of cats in the cat family was put on the ark from which lions, tigers, cheetahs, leopards, pumas, caracals, jaguarondis, servals, ocelots,⁵ and other species of cats evolved to make the thirty to forty known cat species in the world today, including domesticated cats. In the same way, a pair of canines, a pair of horses, and pairs of other kinds of animals were also brought onto the ark, and each pair produced the different species of each kind, or baramin, that are observed today. The effect of this is that the number of animals that Noah had to preserve on the ark is minimized, presumably allowing enough space to care for and feed them.

Conventional geology and paleontology recognizes that there are as many as fifty million Linnean species living today,⁶ including thirty million modern insect species for which 73,000 have been described.⁷ Furthermore, it also must be recognized that much greater numbers of animal species once lived on ancient Earth. According to YECs, these were supposedly buried in sedimentary rocks deposited by Noah’s Flood. So what is seen today is only a tiny part of the vast majority of life that once lived on Earth. Within the context of an ancient Earth and our understanding of the geologic column, the number of buried and extinct species in the fossil record could perhaps have been more than five billion different species or organisms.

Cetaceans and Sea Reptiles—Numerical Relationships

To illustrate the vastness of the fossil record, consider the cetaceans and the extinct sea reptiles. There are eighty-eight living species of cetaceans, which include whales, dolphins, porpoises, and other related species. Some of the more than 150 extinct species of cetaceans in the fossil record are as old as the Eocene Epoch. Therefore, these are found only in the very top of the fossil record.⁸ But note that before the Paleocene, just sixty-six million years ago, not a single whale fossil has been identified in the fossil record. Instead, what is observed in the fossil record is a diversity of sea reptile fossils. The Triassic, Jurassic, and Cretaceous Periods of the Mesozoic Era are known as the Age of the Dinosaurs, but these periods also should be known as the Age of Sea Reptiles. (See geologic time scale, Figure 1.) All these sea reptiles filled the same ecological niches that the cetaceans now fill—deep water, mid-level water, and shallow water. Some had the same shapes as whales, dolphins, and porpoises, except that they had sharp teeth, whereas most cetaceans lacked teeth. There are more than 500 different species of sea reptiles currently recognized in the fossil record.

If it were true that Earth is 6,000 years old, as the YECs claim, and if every kind of animal were created during the Genesis Week (including whales, “the great sea monsters,” as reported in Genesis 1:21), wouldn’t it be remarkable that somehow all sea-living cetaceans survived the flood but not a single sea reptile did? Even then, only a particular set of eighty-eight cetaceans survived that are living today. Of the 550 extinct sea reptiles, there are 200 species of ichthyosaurs, 250 species of plesiosaurs, and 100 species of mosasaurs. One species of mosasaur was sixty feet long. The mosasaurs lived only in the Cretaceous Period, so not all extinct sea reptiles lived at the same time. Other sea reptiles appeared at different times in the Mesozoic Era and then became extinct. Moreover, not all cetaceans lived at the same time, and some became extinct at different times. This distribution of fossils begs for an explanation.

It should be apparent why the young-Earth creationists have been unable to explain why no one has ever found a whale fossil bone in Noah’s Flood deposits, as explained above, when whales must have been living during Noah’s Flood, having been created well before Noah. How could Noah’s Flood separate out free-swimming cetaceans from free-swimming sea reptiles, so that the cetaceans still remained alive after the flood whereas the sea reptiles became extinct and preserved as fossils, particularly when both animal groups had to be living at the same time? Moreover, if they both were living at the same time, how would these creatures have been able to compete in the same environments for food? Both groups appear to be adapted to similar environments. Within the context of an ancient Earth, these patterns are easy to explain. Sea reptiles lived and died well before mammals adapted to living in the sea and became the many species of cetaceans that are alive today. These two groups never lived together and, therefore, never competed for the same resources.

Bird Species

There are 9,000 to 10,000 species of birds on Earth today, of which there are 1,500 species of passerines. Passerines are birds that have feet adapted for perching, such as songbirds. Examples are sparrows, cardinals, gold finches, tanagers, snow buntings, finches, warblers, and blue birds. But perhaps 10,000 extinct species of birds have been found in sedimentary rocks, most of which were supposedly deposited after Noah’s Flood, 4,350 years ago. Jean Lightner⁹ suggested that there were 196 pairs of bird kinds on the ark, including ducks, owls, hawks, shore birds, woodpeckers, etc., that supposedly evolved to produce the 10,000 species of living bird types today. To produce 10,000 species of birds from 196 pairs of birds in just 4,350 years is amazing in itself, but even more incredible, these initial birds also must have given rise to an additional 10,000 species of extinct birds in less than 4,350 years because their fossils are found in what most YECs believe are post-flood rock deposits. This great number of birds would require super-speed or ultra-fast evolution that modern studies of rates of genetic changes in the DNA code do not support.

Elephant Species

Five species of elephants have lived in the modern or near-modern era (three different elephant species, mastodons, and woolly mammoths). But there are more than 150 species of elephants, more broadly known as the proboscideans, that are extinct, including the mastodons and woolly mammoths. Presumably, an ancestral pair to all these elephant species was brought onto the ark. One of these extinct elephants was Deinotherium (see Figure 2), which was a much larger animal than the modern elephant.¹⁰ It had downward projecting tusks instead of curved upward-sweeping tusks. Some elephant species had four tusks.

Thousands and thousands of fossils of Deinotherium elephants have been found in a hundred different locations—Africa, Asia, and even Jordan, Arabia, and Mesopotamia (Iraq) where Hebrew tribes once lived before and after the supposed Noah’s Flood.¹¹ Thousands and thousands of fossils of each of the other 150-plus species of elephants have also been found. Therefore, millions of individuals of these many different elephant species must have lived at one time because only a few of these animals could be expected to be preserved as fossils.

A point that young-Earth creationists must consider is that if Deinotherium were living before and after the flood, why did people living in either time not draw any pictures of them or describe them in the Bible, particularly because Deinotheria are found as abundant fossils in the areas where early Hebrew tribes were living? However, a Google search for cave images of mammoths shows that many such images are found. Moreover, if all these elephant kinds evolved from just a pair of a generic elephant kind, then evolution would have been at a super-speed or ultra-fast to create over 100 species of elephants, including the mammoth.

As many as ten million mammoth fossils are believed to be preserved in the permafrost in the tundra in Siberia, including a complete frozen carcass of a young mammoth with buttercups still found in its stomach.¹² Why are so many mammoth fossils found? These animals must have been living, perhaps near the end of the Ice Age, when a tongue of ice from a glacier flowed across a valley to block the flow of water in the valley. The ice dam created by this blockage then caused a large lake to backup in the valley behind the dam, and the water in the lake must have increased in depth as water continued to flow down the valley from higher elevations. Eventually, the level of the water rose behind the ice dam sufficiently to cause the ice to float. When that happened, suddenly the water, with great depth and under high pressure, rushed out underneath the ice to cause a huge flood, called a jökulhlaup (an Icelandic term), which is a high wall of water that rushes down the valley. If a large herd of mammoths were grazing in a flood plain down-valley, they could suddenly be overwhelmed by this flood and become buried and eventually frozen in the flood debris. Many such jökulhlaups could have happened repeatedly through hundreds of years, so that many herds of mastodons could have been buried to produce the millions of mammoth fossils. Therefore, because millions of fossils of mammoths have been found in Siberia, there also must have been super-speed growth-rates for all these mammoths to be reproduced in less than 4,350 years.

Consider also the rate of population growth of large herbivores. It is generally known today how fast elephants reproduce to create offspring—it takes many years. Some do not begin to reproduce until they are twenty years old and then only have offspring every five to six years.¹³ Therefore, to produce several huge herds of millions of mammoths that YECs require in a short time frame would require idealistic population growth including no death before bearing young, maximum birth rates, and always being able to find a mate to name a few. Thus, more time would have been required than creationists allow for in their chronology of Earth. Moreover, there must have been other large herds of mammoths that were not caught in sudden floods and buried. Therefore, it is even more evident that such a growth-rate cannot occur to produce this many mammoths in less than 4,350 years.

Further Considerations

As I have indicated, there are thirty to forty living cat species, including domesticated cats, all of which biblical literalists believe evolved from a pair of cats on Noah’s ark. But there are 150 species of extinct cats, including the saber-toothed tiger. Presumably, a male and female of one of these extinct cats were put on the ark to evolve to the thirty to forty living species. There are five species of rhinos living today and more than 100 extinct species. There are five to forty species of canines and more than 200 extinct species. There are seven species of living horses and 150 extinct species. There are eight species of living bears and sixty-three extinct species. There are seventeen species of living penguins and more than fifty extinct species.¹⁴ Whatever family of animals is selected, there are many, many more extinct species. Of course, one could say God could produce his creation instantaneously, but if God used his natural laws, then it seems illogical that he would be producing instant creations over and over again throughout the geologic column of sedimentary rocks or during biblical times. On that basis, one is forced to come to the conclusion that if God created billions of creatures, he needed much more time than 4,350 years so that these creatures could evolve into the different kinds of animals. He could not have crammed all these creatures into such a short period of time, obey his natural laws, and leave enough time for them to reproduce and evolve to form different species. This realization of a time limitation also means that logically all of the above observations indicate that a worldwide Noah’s Flood never happened and that Earth must be more than 6,000 years old, particularly because no cetacean fossils have ever been found with sea reptile fossils.

Plant Species

The diversity of animals through time has been well described, but plants tell us a similar story. In China, plant fossils have been found in an ash layer about a meter thick between two coal layers. This ash layer has been excavated over a large area and carefully mapped to locate where different plants, insects (such as dragon flies), salamanders, and frog fossils were found.¹⁵ Artist images of this ancient forest can be seen in a 2012 paper by Jun Wang and colleagues (Wang et al. 2012).

During some ancient time (for a period of perhaps a week) a nearby volcano exploded in a catastrophic event and sent out hot ash that killed all plant and animal life in this area containing a former forest community. Because this happened and has been examined carefully, a snapshot of what life was like in Permian time, 300 million years ago, has been obtained. An ecosystem of plants, insects, and animals for this particular area in China is revealed. But what is present here is not just a local ecosystem that did not exist any place else, because these same fossils are found in other parts of the world in ash and other rocks of the same age.

Volcanic ash is particularly good at preserving plant fossils without any disturbance of how these plants once grew relative to their neighbors. The image of leaf fossils in Figure 3 demonstrates how very delicate leaves can be exquisitely preserved when surrounded and covered by falling ash. In contrast, if these leaves had been deposited in sediments that were transported in rushing water of a tsunami generated during Noah’s worldwide flood, they would have become broken and mixed together as unrelated fragments of different plants. Among the plant fossils in China are tree ferns, lycopods (scale trees, Lepidodendron, now extinct), cycads, and horsetails. Some former, fully grown, but fallen scale trees that were buried flat in the ash give evidence that these trees sometimes were as much as 100 feet tall. Likely, in this same environment, leaves falling off the scale trees and cycads in this ancient forest settled into swamp water, and the low oxygen content of this water prevented bacterial decay of the leaves so that the leaves accumulated to several feet of thickness. Eventually, this carbon-rich plant material became compressed after deep burial under other sedimentary rocks, and at higher temperatures and pressures was converted into coal.

Note that the accumulation of leaves that eventually became compressed to form coal is typically a slow process that could not have been expected to occur quickly during the one-year Noah’s Flood. Moreover, in the leaf fossil-bearing site in China, there are two separately formed coal beds so that there had to have been a long period of time for the regrowth of a new forest community on top of an older forest community that was killed by the falling hot ash. The time for regrowth must necessarily have been more than a year because to grow 100-foot Lepidodendron trees to supply the leaves that later became coal would have taken this greater length of time. Furthermore, in Illinois, there are as many as fifteen different coal seams of Pennsylvania age that are separated from each other by layers of flood-plain muds and river-channel sands, where ancient rivers once eroded through these coal seams in many places.¹⁶ Meandering river channels cannot have been produced by a tsunami created by Noah’s supposed worldwide flood. Moreover, the growth of fifteen different Lepidodendron forest communities in the Illinois area (Dimichele and Phillips 1985), which are on top of each other, would have each required more than a year to grow the tall trees—again to supply the leaves that later became coal. On that basis, the Pennsylvanian rocks in Illinois, like the Permian rocks in China, cannot have been deposited by Noah’s flood that lasted one year, and the flood could not have been worldwide because neither place shows tsunami-like debris.

Furthermore, in the Permian rocks that contain the two coal seams in China, there are no fossils of birds, mammals, dinosaurs, flowering plants, or conifers. It is an exotic and a specific type of forest community. Conifers (gymnosperms) did not appear until the late Permian to the early part of the Mesozoic Era (Triassic), and flowering plants (angiosperms) did not appear until late in the Mesozoic Era, in the Cretaceous Period.¹⁷ So, pollen from the conifer and flowering plants are not found in the volcanic ash of early Permian age, which preserved this ancient forest. If these rocks were deposited during Noah’s Flood, the conifers and flowering plants should also have been alive at the same time because young-Earth creationists claim that Mesozoic rocks were deposited during this flood, and the winds that blew the ash should also have carried tiny, wafted, pollen grains from living conifers and flowering plants to the site that contains the lycopods and cycads, and that did not happen.

At any rate, volcanic ash is an excellent medium for preserving plant fossils, and because of the preservation of the forest plants in ash in China and in many other places around the world, this worldwide distribution of plant fossils give evidence of a quiet setting that clearly shows that a worldwide Noah’s flood never happened. Even though young-Earth creationists believe that the Permian Kaibab limestone formation in the Grand Canyon was deposited by Noah’s worldwide flood (Hill et al. 2016), the Permian ash beds in China, containing wonderfully preserved, unbroken, plant-leaf fossils, clearly shows that all the Permian rocks in the world cannot have been deposited by a worldwide flood.

Summary and Conclusions

The following nine observations of biological relationships provide strong evidence that the young-Earth creationists’ worldwide flood 4,350 years ago is unsupported and that Earth is far more ancient than they claim if God’s natural laws are obeyed.

1. Numbers of species in the geologic record are so large that not enough time could exist for God to create them by evolutionary changes in the DNA coding and for the animals to reproduce to form millions and millions of living creatures in less than 6,000 years and for huge numbers of species to evolve from only pairs of kinds or baramins on Noah’s ark in the time following 4,350 years ago to the present.

2. No cetacean fossils (bones of whales, dolphins, and porpoises) in Mesozoic rocks coexist with fossils of sea reptiles, and both animal types must have been living at the same time when Noah’s Flood supposedly occurred if the YEC model were correct.¹⁸

3. Extinct species of animal families far outnumber those living today. This makes it very difficult to have all these species created on Earth in 6,000 years and for many species to have been created after a supposed worldwide Noah’s Flood occurred about 4,350 years ago.

4. Too many bird species exist (9,000 to 10,000) for them to have evolved from 169 pairs of birds on Noah’s ark or for as many as 10,000 additional extinct species to have evolved from a single pair of birds prior to Noah’s Flood in 6,000 years.¹⁹

5. Too many elephant species (150-plus) exist for them to reproduce and increase to herds of millions and millions of animals in 4,350 years after Noah’s Flood and particularly for tens of millions of mammoths to have been created in that short time.

6. Ecosystems of plant, insect, and animal species of Permian age preserved in volcanic ash in China and in other volcanic ash and rocks of the same age in other places around the world (the ecosystem in China is totally undisturbed) indicate that such plant and animal communities could not have been buried in sediment transported by a tsunami generated by a worldwide Noah’s Flood.

7. Pollen is not found in the ash in the preserved forest ecosystem in China when wind that blew this ash should have also blown pollen wafted from conifers and flowering plants that must have been alive at the same time, according to the model of the YECs.

8. The growth of a new forest community in China to produce a second, meter-thick, coal seam cannot have been produced in one year after a former forest community was killed by ash, and, therefore, these Permian rocks cannot have been buried during the supposed worldwide Noah’s Flood.

9. The occurrence of fifteen different coal seams in Pennsylvanian rocks in Illinois, which are in sequential layers on top of each other and the time (far more than one year) that it would take for Lepidodendron trees to grow to 100-feet to produce the leaves that later convert to coal for each of the fifteen coal seams means that these Pennsylvanian rocks cannot have been deposited in the one year in which Noah’s worldwide flood is supposed to have occurred.

Because contemporary young-Earth creationists have said that the Bible must be literally interpreted, they have made all the wrong interpretations listed in the above nine conclusions about animals and plants that were buried in sediments deposited during the supposed worldwide Noah’s Flood.

Biological Reasons Consistent with Physical Geologic Reasons

All biological reasons a worldwide Noah’s Flood never happened described in this article are consistent with physical geological reasons a worldwide flood never happened, published in my earlier Skeptical Inquirer article (Collins 2018). (See also my follow-up “Response to Ken Ham and YouTube Comments by Andrew Snelling,” SI, July/August 2018, pp. 56–58.) They all give the same conclusion: that a worldwide flood never happened and, on the basis of erosion rates in rocks in the Grand Canyon in Arizona, Earth cannot be 6,000 years old (Collins 2018). Nevertheless, a local large flood in biblical times could have happened (Collins 2009). Not included in this article are supporting studies that also indicate that Earth cannot be 6,000 years old.²⁰

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Acknowledgements

I thank Glenn Branch from the National Center for Science Education for many helpful editorial suggestions, Joel Duff from the University of Akron for many useful editorial changes, and Forrest Hopson for several critical comments.

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Notes

1. The Creation/Evolution Continuum, National Center for Science Education https://ncse.com/library-resource/creationevolution-continuum.
2. Tony Ortega, How many Americans actually believe the earth is only 6,000 years old? https://www.rawstory.com/2013/11/how-many-americans-actually-believe-the-earth-is-only-6000-years-old/.
3. In U.S., belief in creationist view of humans at new low. May 3–7, 2017. http://news.gallup.com/poll/210956/belief-creationist-view-humans-new-low.aspx.
4. Baraminology, Answers in Genesis. https://answersingenesis.org/creation-science/baraminology/.
5. Cat species not commonly known include the caracal (a Chinese desert cat), the jaguarondi (found in southern North America and South America), the serval (a native of Africa in sub-Saharan countries), and the ocelot (found in South America), all of which tend to hunt at night.
6. Number of Living Species in Australia and the World, second edition. Australian Department of the Environment, Water, Heritage and the Arts, https://www.environment.gov.au/system/files/pages/2ee3f4a1-f130-465b-9c7a-79373680a067/files/nlsaw-2nd-complete.pdf.
7. Numbers of insects (species and individuals), Smithsonian. https://www.si.edu/spotlight/buginfo/bugnos.
8. Evolution of cetaceans. https://en.wikipedia.org/wiki/Evolution_of_cetaceans.
9. Jean Lightner, An Initial Estimate of Avian Ark Kinds, Answers in Genesis, https://answersingenesis.org/creation-science/baraminology/an-initial-estima.
10. Deinotherium, New Dinosaurs. https://www.newdinosaurs.com/deinotherium/.
11. Robert Joel Duff, one-hour YouTube programs titled: Part II Scientific Apologetics, Historical Science and the Fossil Record. Available online at https://www.youtube.com/cha\nnel/UCKFGXH_YUdWE-n9kSV5sg3Q.
12. Tia Ghose, Fresh mammoth carcass from Siberia holds many secrets. Scientists will examine the mammoth to learn whether it will yield enough undamaged DNA to make cloning the extinct creature a reality, LiveScience, https://www.scientificamerican.com/article/fresh-mammoth-carcass-from-siberia-holds-many-secrets.
13. Maina Waruru, Slow-to-breed elephant hurtles towards extinction, https://www.newscientist.com/article/2103783-slow-to-breed-elephant-hurtles-towards-extinction/.
14. Robert Joel Duff, one-hour YouTube programs titled: Part II Scientific Apologetics, Historical Science and the Fossil Record. Available online at https://www.youtube.com/cha\nnel/UCKFGXH_YUdWE-n9kSV5sg3Q.
15. A “Permian Pompeii” Chinese Fossil Site Preserves Ancient Permian Ecosystem, Everything Dinosaur, https://blog.everythingdinosaur.co.uk/blog/_archives/2012/02/22/a-permian-pompeii.html.
16. Coal geology of Illinois, Keystone Coal Industry Manual, https://www.isgs.illinois.edu/sites/isgs/files/files/coal-maps/Illinois-coalgeology.pdf.
17. Evolution of forests and trees—Understanding how Earth’s first forests developed, ThoughtCo., https://www.thoughtco.com/evolution-of-forests-and-trees-1342664.
18. Understanding Evolution—The evolution of whales. https://evolution.berkeley.edu/evolibrary/article/evograms_03.
19. Understanding Evolution—The origin of birds. https://evolution.berkeley.edu/evolibrary/article/evograms_06.
20. Robert Joel Duff, one-hour YouTube programs titled: Scientific Apologetics, Origin vs. Operational Science that discusses the erosion of boulders in the Atacama Desert in Chile. Available online at https://www.youtube.com/cha\nnel/UCKFGXH_YUdWE-n9kSV5sg3Q.

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References

• Collins, Lorence G. 2009. Yes, Noah’s flood may have happened but not over the whole earth. Reports of the National Center for Science Education 29: 38–41.
• ———. 2018. Twenty-one reasons Noah’s worldwide flood never happened. Skeptical Inquirer 42(2) (March/April): 50–53.
• Dimichele, William A., and Tom L. Phillips. 1985. Arborescent lycopods reproduction and paleoecology in a coal-swamp environment of late Middle Pennsylvanian age (herrin coal, Illinois, U.S.A.). Review of Palaeobotany and Palynology 44(1–2): 1–26. Available online at https://www.sciencedirect.com/science/article/pii/0034666785900260.
• Hill, Carol, Gregg Davidson, Tim Helble, et al. (eds). 2016. The Grand Canyon—Monument to an Ancient Earth: Can Noah’s Flood Explain the Grand Canyon? Grand Rapids, MI: Kregel Publications.
• Wang, Jun, Hermann W. Pfefferkorn, Yi Zhang, et al. 2012. Permian vegetational Pompeii from Inner Mongolia and its implications for landscape paleoecology and paleobiogeography of Cathaysia. Proceedings of the National Academy of Sciences 109(13): 4927–4932. Available online at http://www.pnas.org/content/early/2012/02/14/1115076109. For artist drawings, see http://www.pnas.org/content/109/13/4927.figures-only.