Islands and lost worlds, from the Odyssey to Arthur Conan Doyle

In a world where wonder hijacks you when you least expect it, connections abound. Like between the Odyssey and Arthur Conan Doyle, via Darwin and genetic studies.

It’s the islands

The Odyssey, composed by and for a sea-faring culture, is brimming with islands in a wine-dark sea. The story reminds us of something Darwin later used to develop his theory of natural selection.

Islanders- be they people, plants or animals- are isolated. That isolation means they adapt to their environment with relatively little influence from elsewhere. (Is anyone thinking finch beaks?)

The island hidden by a ring of mountains

Odysseus at the court of Alcinous by Francesco Hayez, 1814-1815, in Galleria Nazionale de Capodimonte, Source, The Yorck Project, via Wikimedia Commons.
Odysseus at the court of Alcinous (1814-1815) by Francesco Hayez in Galleria Nazionale de Capodimonte.  Odysseus is the one crying. Source: The Yorck Project, via Wikimedia Commons.

Odysseus visits many strange islands in his ten-year trip home.  When he washes ashore in Scheria, the gracious Phaeacians welcome him with great hospitality. The king, Alcinous, and his court listen to his story and bestow him with gifts. Then they take him to Ithaca. Home, at last!

One of the reasons it’s taken so long for Odysseus to return to Ithaca is because he provoked Poseidon by blinding his son, Polyphemus. When the god of the sea learns the Phaeacians have helped Odysseus, he punishes them by turning the ship that carried him home to stone.

Poseidon also wanted to lift a ring of mountains around their island, but Zeus discouraged him. The mere sight of the ship “rooted in stone” just off the harbor is warning enough for the Phaeacians to never take castaways in their ships again.

If Poseidon had surrounded Phaeacia with mountains it would have been completely cut off from the rest of the world. No chance to travel. Nor to receive travelers. A tragic fate for a nation that lives by trade.

And like islands, thus mountains

Since mountains are higher than the surrounding land, their summits and slopes tend to be colder and wetter. Animals and plants adapted to these different conditions are effectively isolated. For this reason, the distribution of organisms (also known as biogeography) of mountains is like that of islands.

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A tepui in the Canaima National Park of Venezuela. Photo by DamianFinol via Wikimedia Commons.

Tepuis are found in southern Venezuela, north- eastern Guyana, southern Suriname, and northern Brazil. They’re tall (1000 to 3000m) and their sides are steep cliffs.

Tepuis are also ancient…

Now, age is pretty relative when we talk about tepuis, as you’ll soon see.

Tepuis are the remnants of a sandstone massif that covered the continent of Gondwana 450 million years ago. After Gondwana broke up into Africa, America and Eurasia, the sandstone eroded and became a series of tabletop mountains 70 to 90 million years ago.

Tepuis are Sky Islands 

Like islands, they represent a fragmented habitat for plants and animals. More than half the vascular plants (ones that have support tissues) are endemic, that is, they’re only found there, as are many animals.

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In the Pixar movie Up, the characters travel to a tepui in a house carried by balloons. Cool, huh! I wonder if the wonderful imaginary bird Kevin was a Lost World relic.

Inspired by their age and strangeness, Arthur Conan Doyle (yes, the creator of Sherlock Holmes) wrote about dinosaurs roaming the tepuis in his novel The Lost World.

No sign of dinosaurs so far

But, given the abundance of endemic species, scientists have proposed the Lost World hypothesis, whereby the ecosystems on the summit may have been there since before the tepuis separated (70-90 million years ago).

Others assert that the isolation hasn’t been absolute. Organisms could have moved between different elevations on a given tepuis. Birds, insects and (seeds of) flowering plants may have gone to other tepuis by air: island-hopping.

So a good test of the Lost World hypothesis would be an animal unlikely to island-hop, say a tree frog.

What the tree frog told us

According to a 2012 genetic study, four species of the tree frog Tepuihyla shared an ancestor less than 5.3 million years ago. Some of the studied populations were separated as recently at 2.5 million years ago.

Excuse me, is that recent? Um, yes, compared to 70 million years. Most importantly it falsifies the Lost World hypothesis for this tree frog genus.

Other populations of Tepuihyla appear to have moved up or down the slope a few thousand years ago coinciding with changes in climate.

For more information, Carl Zimmer wrote an excellent NYTimes article on the study.

The Lost World hypothesis is not completely disproven

There may be populations that were separated when the tepuis formed, but the genetic studies haven’t been carried out. What has been proven is that the ecosystem includes recent additions.

Back to the Phaeacians

In other words, if a ring of mountains had been raised by Poseidon to isolate the island of the Phaeacians, it wouldn’t have been impenetrable. As Arthur Conan Doyle put it in The memoirs of Sherlock Holmes (1893):

“Excellent,” I cried.

“Elementary,” said he.

 

 

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