How Did Noah’s Ark Float?

Jesse becomes engaged in the Creationism discussion, when asked
whether all life might actually voyage on Noah’s Ark, as reported
in an article Reuters’ excellent environment
correspondent, Alister Doyle.

FEATURE-How did Noah’s Ark float? New species cram aboard

Thu May 15, 2008 8:04am EDT

By Alister Doyle, Environment Correspondent

OSLO, May 15 (Reuters) – How did Noah’s Ark manage to stay afloat?

Estimates of the number of species on earth are surging into apparently hull-busting millions as biologists find new life almost everywhere they look, from African swamps to Antarctica.

The ever-widening menagerie is a paradox when an expanding human population, pollution and climate change threaten what United Nations’ studies say is the worst spate of extinctions since the dinosaurs were wiped out 65 million years ago.

Government officials trying to protect the modern world’s wildlife gather in Bonn from May 19-30 for a meeting of the U.N. Convention on Biological Diversity, to examine progress towards a goal set in 2002 of slowing biodiversity loss by 2010.

Most experts say the target is slipping out of reach.

Even so, wider research means finds of new species such as a legless lizard in Brazil or a Tanzanian shrew are testing biblical scholars’ calculations on how Noah squeezed all animals aboard the Ark.

“It’s of course physically impossible,” James Edwards, executive director of the Encyclopedia of Life, said of the biblical account.

The Encylopedia is cataloguing all identified species, 1.8 million so far, in a free online service (https://www.eol.org/).

“There are expectations of 8 to 50 million more species out there that we haven’t identified yet,” Edwards said. Other experts’ estimates of the numbers range up to 100 million.

But the newly found species do not compensate for extinctions.

Sigmar Gabriel, environment minister for the U.N. conference host Germany, said last week that the loss of species threatened food supplies for billions of people. He cited marine life, saying that if nothing was done there would be no commercial fishing by 2050.

Extinctions of recent decades include Australia’s southern gastric brooding frog — the females could shut off their stomach juices to raise young in their stomachs, a trick that could have held clues for curing human ulcers.

Believers in the Bible note that the Ark described in the Book of Genesis was a giant ship by ancient standards about 140 metres (460 ft) long — far from the tiny vessel depicted in many children’s books with giraffes’ heads sticking out the top.

In the biblical account, Noah safeguarded life on the planet after God, upset by the wickedness and violence of mankind, sent a devastating flood. “Everything on earth will perish,” God said, according to the Bible.

ALL CREATURES

Noah only took along land creatures and birds, not plants nor fish that make up a large part of the world’s total species.

“We’re talking about something plausible here,” said David Menton, an associate professor emeritus of anatomy at Washington University who works for Answers in Genesis, founder of a controversial Creation Museum in Kentucky.

The museum, which opened last year, depicts the Bible’s first book, Genesis, as literal truth. Its exhibits have been welcomed by those who believe that God created the heavens and the Earth in six days about 6,000 years ago.

Menton reckoned that Noah probably only had to take aboard about 16,000 creatures and said that most projected species discoveries are of tiny organisms.

“And we can leave out all organisms known to survive extensive flooding — such as insects and worms,” he said.

Even though creationists reject evolution, Menton said Noah may have taken along pairs to represent closely related “kinds” of animals such as dogs, wolves, coyotes and dingos, or just one pair for cows and buffaloes or tigers and lions.

He said Noah might have saved space by bringing along juveniles, including dinosaurs such as T-Rex or giant sauropods that could grow up to 30 metres (98 ft) long. Creationists believe that dinosaurs co-existed with humans.

The dimensions of the wooden Ark, given in cubits in the Book of Genesis, imply it was about 140 metres long, 23 wide and 13.5 high. It had three levels, meaning a total deck space of just short of 10,000 square metres (107,600 sq ft).

“The cargo capacity of such a ship would be impressive for those times and could be as large as 30,000 tons,” said Dragos Rauta, an expert at the International Association of Independent Tanker Owners (INTERTANKO).

Even so, the vessel would struggle to comply with modern marine transport guidelines, even with a few thousand creatures.

Noah and his family took along at least two of every type of animal and bird, and food for all on a voyage that lasted for months. The Bible also says that “clean” animals, or those deemed fit for eating such as cattle, sheep and goats, were taken in sevens.

Bjorn Clausen, managing director of Danish livestock shipping experts Corral Line AS, said large cows need at least 2 square metres each when held in pens for half a dozen animals.

“For animals like tigers, I’m not an expert but I’d say if you sail you’d need at least 4 square metres for a single tiger,” he said. What with other big animals such as kangaroos and rhinoceroses, the Ark would have quickly filled up.

HOT AND COLD

And zebras, penguins, vultures, pandas and antelope all need very different temperatures, food and habitats.

“Noah would have to be a very skilled heating and ventilation engineer … to have polar bears and iguanas on the same boat,” said Jesse Ausubel, chairman of the Encylopedia of Life at Rockefeller University in New York City.

“I’m not sure about the volume but … they wouldn’t all want the same conditions in their cabins,” he said.

The 2005 Millennium Ecosystem Assessment, a study by more than 1,300 scientists, estimated the number of identified species at 1.7-2 million with the final total likely to be between 5 and 30 million.

Of the named species, the biggest group by far, numbering around 1 million, are insects, centipedes and millipedes. Other big groups include plants, vertebrates — such as humans or whales — and molluscs. Mammals alone total more than 5,000 species — a few live in the sea, like whales.

In a line taken by creationists to argue that insects survived outside the Ark, Genesis says “everything on dry land that had the breath of life in its nostrils died” in the flood.

Insects do not have nostrils, so perhaps they survived by floating on uprooted trees or other debris.

Revealing tiny food webs

As Bruegel the Elder recognized in 1557, “big fish eat little fish”. Determining exactly what eats what remains a fundamental question in modern ecology and this task is particularly challenging for biologists studying small organisms, which make up the bulk of the biomass in ecosystems. To add interest, a number of these tiny creatures with unknown diets are medically and/or economically important disease vectors.

The Metropolitan Museum of Art www.metmuseum.org

In Mol Ecol Resources May 2008 researchers from University of California, Irvine, Kenya Medical Research Insitute, and Kanazawa University, Japan, apply DNA analysis identify gut contents of larval Anopheles gambiae complex mosquitoes, the major malaria vector in Africa. 

Photo Richard C. RussellAuthors Garros, Ngugi, Githeko, Tuno, and Yan collected anopheline larva near Kisumu in western Kenya, dissected stomach contents of third and fourth instar forms, extracted DNA, and amplified an 800 bp fragment of nuclear 18s rRNA. A separate PCR assay was used to confirm species identity (five were A. gambiae s.s. and 68 were sister species A. arabiensis). According to authors, 18s rRNA was analyzed rather than COI because “more sequences are available [for 18s than for COI] in databases for plants, fungi, and protists”. I note there are now many research groups working on “plants, fungi, and protists” so it should be possible to achieve greater resolution in this sort of study as the DNA barcode libraries are built up.

The PCR products from gut contents were first screened with a restriction endonuclease known to digest mosquito but not algal 18s.  355 PCR products from eight randomly selected larvae were screened, yielding 14 unique non-mosquito sequences. Best matches in GenBank blast results clustered into 3 main clades: green algae (7), fungi (5), and unknown eukaryotes (2). The authors conclude “the method presented in this study may be a promising tool to investigate natural diets of [anopheline] larvae”. Looking ahead, “such studies will not only improve our understanding of Anopheles larval ecology, but also provide fundamental information to facilitate the develpment of novel larval control tools.”

This study is one demonstration of how routine DNA analysis combined with expanding DNA barcode libraries will help reveal and monitor changes in a multiplicity of tiny food webs. More generally, routine DNA analysis combined with reliable DNA reference libraries opens wide avenues for rapid progress in understanding how the diversity of organisms interact, with benefits to society and science. Continued development of robust, inexpensive methods for analyzing DNA from the various types of biological samples and methods of matching the results to well-curated DNA reference libraries will speed this along.   

Finding frogs with DNA

Knowledge of how species are distributed is essential for understanding evolution and ecology, and monitoring enables detecting invasive species and recognizing effects of biological and physical environmental change. That’s easy to say, but many species are small, secretive, or difficult to distinguish from one another, so mapping species distributions requires enormous human effort and ongoing monitoring requires even more. I venture a guess that we have good monitoring for 10,000 or so plant and animal species, mostly large animals and those plants and animals of economic importance, and static distribution maps for about 100,000 species, out of a total of 1.7 million named species and not counting the projected total of 10 million species that might eventually be recognized when surveying biodiversity approaches completion. 

Just as high-resolution satellite mapping has surpassed most ground surveys in accuracy, speed, and cost, we need efficient technologies that can help detect and monitor species from environmental samples. In 9 April 2008 Early Online Biol Lett researchers from Universite Joseph Fourier and Universite de Savoie, France, and Universita Milano Bicocca, Italy, apply high-sensitivity DNA analysis to detect presence or absence of American Bullfrog Rana catesbeiana, a globally invasive species. PCR amplification of a diagnostic 79 bp fragment of mitochondrial gene cyt b using species-specific primers (no amplification of samples from the 5 locally native Rana sp). Three 15 mL water samples were collected from each of 9 ponds (surface area 1000-10,000 m^2) in France, including “three ponds where bullfrogs were present at low density (one to two adults seen, no reproduction), three ponds where bullfrogs were present at high density (dozens of adults and thousands of tadpoles), and three ponds where bullfrogs have never been detected.” Each sample was analyzed 3-5 times, giving 9-15 repeats per pond. R. catesbiana DNA was never detected in the ponds with no bullfrogs and was detected in water samples from all three high-density ponds, with most (79%) of replications positive. Bullfrog DNA was also detected in all low-density ponds, although fewer of the replications were postive ( 37%).

Ficetola et al observe “our approach allows the reliable detection of secretive organisms in wetlands without direct observation.”  The authors conclude “The ongoing effort to develop DNA barcodes for identifying species  from degraded DNA (Hajibabaei et al 2006; Taberlet et al 2007) will make our approach applicable to more and more plant and animals species…These factors will soon make possible the assessment of the current biodiversity of macro-organisms from environmental samples.” 

Like satellite mapping 20 years ago, DNA-based environmental monitoring of biodiversity, aided by growing DNA barcode libraries, is set to expand rapidly.

Detecting aliens with DNA

Alien species sometimes damage native landscapes. In Voyage of the Beagle, in entry dated September 19, 1832, Darwin describes the spread of an introduced European thistle Cyanara cardunculus in Banda Oriental, now Uruguay: “very many (probably several hundred) square miles are covered by one mass of these prickly plants, and are impenetrable by man or beast. Over the undulating plains, where these great beds occur, nothing else can live…I doubt whether any case is on record, of an invasion on so grand a scale of one plant over the aborigines.”

The challenge is to recognize invasive species before they become established. In 11 January 2008 Polar Biology researchers from Stellenbosch University and University of Western Ontario apply DNA barcoding to otherwise unrecognizable moth larvae on sub-Antarctic Marion Island. The indigenous Lepidoptera on Marion Island comprises 2 or 3 flightless moths, and the occassional adult winged moths or butterflies have been assumed to be transients arrived on fresh produce.

In April 2004, 3 noctuid moth larvae were found in an abandoned Wandering Albatross nest, a common habitat for one of the indigenous moth species. The larvae could be tentatively identified only to genus level and so rearing was attempted, with one larva dying after several months of pupating (as an aside, this is one example of how morphologic identifications can be laborious and/or incomplete, even for experts). The final larva was killed and preserved for DNA study; COI DNA barcode region was amplified using standard Folmer primers. The Marion Island moth larva barcode clustered with the 40 or so Black Cutworm Agrotis ipsilon sequences in BOLD, and was distinct from COI sequences of the other 18 Agrotis species in BOLD. Agrotis ipsilon is a common pest that feeds on a wide variety of plants. The authors conclude that Agrotis ipsilon is an established alien species with the potential to disrupt local ecosystems and that “steps be taken to eradicate the species from Marion Island.”

It is easy to predict that rapid identification of potential invasive alien species will be a major application of DNA barcoding, with direct economic and ecosystem benefits.

TED Conference

The Technology-Entertainment-Design (TED) conference that helped launch the Encyclopedia of Life and connect it with hi-techsters prepared a 4-minute, 13 MB video [download it here] that both reports on progress and shows some nifty features in store for future EOL users.

Routine DNA ID as quality control in ecology and evolutionary biology

photo Colorado Division of WildlifeJust as DNA analysis regularly overturns seemingly solid eyewitness identifications in crime investigations, routine DNA analysis can also help biologists avoid blunders. In 28 August 2007 Mol Ecol, researchers from University of Colorado, New Mexico State University, Pisces Molecular, and Brigham Young University report that over 20 years of restocking efforts in western US aimed at restoring native populations of endangered greenback cutthroat trout Oncorhynchus clarkii stomias have mostly been restocking a non-native, non-endangered subspecies, Colorado River cutthroat trout O. c. pleuriticus.  They trace the confusion to repeated introductions beginning in the late 1800s of Colorado River cutthroat trout throughout the native range of greenback cutthroat trout. The authors analyzed mitochondrial (COI, ND2) and nuclear (microsatellites, AFLP) DNA from 365 individuals from 15 locations in 3 major river drainage systems in Colorado and surrounding states. Distinct mtDNA lineages corresponding to each subspecies were corroborated by nuclear microsatellite and AFLP data.  For another cautionary tale of repeated misidentification of a widely studied organism, see Siddall and colleagues’ entertaining June 2007 Proc R Soc paper scrutinizing commercially available medicinal leeches sold as Hirudo medicinalis. 

How might the future look with routine application of DNA ID as quality control? Incorporating DNA barcode analysis into Tree of Life studies is one useful approach, exemplified by two recent large-scale evolutionary studies published in January and April 2008 Syst Entomol, one on phylogenetic relationships in Saturnid silkmoths, and one on higher-level relationships among 12 families in ‘bombycoid complex’ of Lepidoptera. Both studies analyze COI barcodes of all specimens, “allowing confirmination of their identification for species present in the BOLD reference library and enabling future identifications of organisms whose identity is still pending.”