Birdwalking into the Miocene

From the One Thing Leads To Another department, we have: a cute little fuzzy mammal from Madagascar, some thoughts about genetic drift, and a period of geological history during which a lot was happening.

I'd like to say that this kind of twisty mental path is infrequent for me, but unfortunately, it happens pretty much on a daily basis, and has since I was a kid.  When I was around twelve years old, my parents splurged on a set of Encyclopedia Brittanica, ostensibly to assist me with my schoolwork, but they (the Encyclopedia, not my parents) were honestly more of a hindrance than a help.  I'd go to the Brittanica to look up, say, something about the Monroe Doctrine for social studies class, and my mom would find me three hours later with fifteen open volumes spread on the floor around me, with me in the middle immersed in an article about venomous snakes in Malaysia.

It's why conversations with my older son, with whom I seem to share a brain, are like some kind of weird exercise in free association.  We've occasionally tried to reconstruct the pathway by which we got to a particular topic, and there's usually a logical connection between each step and the preceding one, but overall, our discussions give new meaning to the word labyrinthine.

Anyhow, today I started on this particular birdwalk when someone posted a photograph on social media of an animal I'd never heard of: the ring-tailed vontsira (Galidia elegans).  The vontsira is kind of adorable:

[Image licensed under the Creative Commons Charles J. Sharp creator QS:P170,Q54800218, Ring-tailed vontsira (Galidia elegans) 2, CC BY-SA 4.0]

The vontsira and its relative the falanouc are in the family Eupleridae along with a species I had heard of, the fossa, which is a sleek, elegant, weasel-like animal that is only distantly related to other members of the Order Carnivora.  All of the eupleurids live in Madagascar, and like most of the endemic species on the island, they're threatened by habitat loss and competition from non-native species.

What I found most curious about these mammals is that they're a clade -- genetic studies have found that eupleurids all descend from a single small population that arrived in Madagascar something like twenty million years ago, and then diversified into the species you see today.  Chances are, the ancestors of the vontsira, falanouc, fossa, and other eupleurids came over from Africa via rafting in the early Miocene Epoch.  They're distant cousins of the much more common and widespread mongooses, hyaenas, genets, and civets, and it was probably some prehistoric viverroid (the parvorder that includes all five groups) that made its way to Madagascar and gave rise to modern eupleurids.

This led me to looking into what was happening, geology-wise, during the Miocene.  I knew it was a busy time, but I didn't realize just how busy.  Tectonic movement closed off the Mediterranean Sea from the Indian Ocean, and then a shift at the western end of the Mediterranean closed off the Straits of Gibraltar; the result was that the Mediterranean dried up almost completely, something called the Messinian salinity crisis because what was left was a salty desert with an average temperature of something like 110 F and two disconnected lakes of concentrated brine.  At the end of the epoch, another plate movement reopened the Straits, and there was a flood of a magnitude that beggars belief; at its peak, the flow rate was enough to raise the level of the refilling Mediterranean by ten meters per day.

This is also the period during which the Indian subcontinent rammed into Asia, raising the Himalayas and introducing a bunch of African species into Asia (this is why there are lemurs in Madagascar and India, but none in the Middle East).  Also, it's when the Columbia River Flood Basalts formed -- an enormous (175,00 cubic kilometers) blob of igneous rock covering what is now eastern Washington and Oregon, and the west parts of Idaho -- an eruption probably due to the same hotspot which now underlies Yellowstone.

Because of all this, the climate during the Miocene might as well have been attached to a yo-yo.  Warm periods rapidly alternated with cold ones, and wet with dry.  As you might imagine, this played hell with species' ability to adapt, and groups came and went as the epoch passed -- the borophagine ("bone-crushing") canids, the terrifying "hypercarnivorous" hyaenodonts, and the enormous, superficially pig-like entelodonts amongst them.  The first apes evolved, and the split between the ancestors of modern humans and modern chimps occurred in the late Miocene, something like seven million years ago.

If all that wasn't enough, some time during the Miocene -- geologists are uncertain exactly when -- there was an asteroid impact in what is now Tajikistan, forming the twenty-five-kilometer-wide Karakul Crater Lake, which at an elevation of 3,960 meters is higher than the much better-known Lake Titicaca.

So there you have it.  A brief tour of the chaotic paths through my brain, starting with a furry woodland animal from Madagascar and ending with a meteorite impact in Tajikistan.  Hopefully you found some stops along the way interesting.  Now y'all'll have to excuse me, because I need to go look up a single fact in Wikipedia to answer a question a friend asked about linguistics.  You'll find me in a few hours reading about how general relativity applies to supermassive black holes.

I'm sure how I got there will make sense to me, at least.

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