How far back do people and cats go?
Too far for a written record of their origins. Today’s experts must use fossils and molecular markers to “read” the past.
The fossil record is incomplete, and molecular markers don’t work on extinct species that have no living descendants.
Nevertheless, we can see broad outlines of the history of people, cats, and the ice ages.
Children of the ice ages
The planet went through two deep-freezes while we and Fluffy evolved:
- What we think of as the Ice Age — the last one, which is called (among other names) the Wisconsin or Würm glaciation. Very generally, this chilly period lasted from about 115,000 to around 10,000 years ago.
- The one before that, a/k/a the Illinoian or Riss glaciation. This one lasted from roughly 350,000 to 130,000 years ago.
In between these two was a warm interglacial similar to the one we’re in now.
There have been many such glacial-interglacial cycles over the last 2.5 million years.
Now, against a background of more than 4 billion years’ worth of Earth history, those icy times aren’t that big a deal. Our planet has seen much colder times.
But they matter to us.
Humanity emerged during the ice ages, and it was during this period that the living world around us took shape.
Two and a half million years is too long a stretch for the mind to grasp, though. Let’s put a face on this story — a round, furry little face.
Cats have been around for some 20 million years, but the oldest known Felis fossil is “only” about four million years old.
What sort of world did that little Pliocene cat inhabit?
In terms of geography, a satellite view of Earth back then would show subtle changes here and there but otherwise be quite familiar.
The big shocker to modern eyes would be the poles: Western Antarctica was freckled with bare ground, and the North Pole was open water!
However, this wasn’t the greenhouse of dinosaur times.
Globally, Pliocene temperatures were only about 10° F warmer than they are today, and there was just a little more rainfall, not those great downpours that watered Cretaceous tropical rainforests.
But Earth, in Felis attica’s day, was cooling down and drying out more and more as time passed.
These changes initially were so gradual that paleoclimatologists now have difficulty reconstructing them from the geological record.
Life on Earth adapted, as it always does. Ecosystems shifted around; some species of animals and plants disappeared, others found ways to survive the climate changes, and a few even prospered.
Then, around 2.5 million years ago, conditions on the planet crossed some sort of a threshold and things began to happen quickly (in geologic terms).
Glaciers appeared in the Northern Hemisphere, and the northern Pacific Ocean cooled dramatically. Huge ice sheets soon formed and spread out over the northern continents, only to melt away and then reappear.
The glacial-interglacial cycle has played out over and over again since then. The only difference now is that humanity is around to experience it.
As the first thick sheets of ice grew and expanded out of centers, possibly in what are now Canada, Scotland, Sweden, and northern Russia, early members of our own primate group Homo (though not yet sapiens) emerged in Africa, where they had to contend with lions, leopards, hyenas, and at least three different kinds of sabercat.
At around the same time but farther north, in Italy, there lived a smaller cat — Felis lunensis.
This 2-million-year-old kitty has left only a few fossils behind in Europe, not enough to explain how it and the first Felis might be related.
Still, there is enough fossil evidence to show paleontologists that F. lunesis was a lot like modern wildcats.
It’s not clear what happened to this small cat after that.
Ice ages, of course, do affect evolution in complex ways.
Gene pools mix, new species form, and older species go extinct or hybridize as animals and plants move away from the advancing ice and then return to their old but now very different neighborhoods when the world warms up again.
Apparently F. lunensis was adaptable enough to see all this through, because Europe is where the first true wildcat eventually appeared.
And, as we’ll see next week, some of these descendants of old lunensis moved out into Africa and the Middle East, where they eventually met and moved in with people at the end of the last ice age.
Featured image: European wildcat in the snow, by Tambako the Jaguar, CC BY-ND 2.0.
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