Time: Human vs. Geological

Life on Earth is strange, and I don’t just mean physically. It’s odd how life goes on here.

In terms of time, we are so out of sync with our planet!

About 75% of the Earth’s outer crust, where we live, is composed of rock similar to this. (Image: James St. John, CC BY 2.0)

First, look at our natural surroundings — steady as a rock (most of the time, anyway).

And usually very, very old.

Then look at humans, or at cats — each born helpless; struggling to reach maturity; struggling more to survive and reproduce; and then aging and passing away.

It all happens quickly, too (at least to an outside observer: parts of our own lives seem to take forever).

In the wild, cats don’t live long, maybe five to ten years, or a little more if they’re tough and lucky.

More beautiful than any rock. (Image: SantiPhotoSS/Shutterstock)

Exceptionally elderly people might live for a hundred years, but even this is short compared to the social fabric that they are wrapped in. While often resembling a patchwork quilt, its history goes back many centuries.

The current British monarch, for example, is in her mid-90s. That isn’t very old, considering how long her royal house has been around, and it’s positively youthful compared to the age of her kingdom.

Still, what do centuries and millennia mean to a multimillion-year-old rock?

Nothing, of course. It’s inert, although there may be something living underneath it or even inside. The rock’s components — silica, oxygen, and various other elements — are just chemistry, facts for nerds to ponder.

Biology is where it’s at, and we’re at the top of the heap!

This delusion is so powerful that most of us need a strong reason to ask the really interesting question — what does that multimillion-year-old rock mean to us?

When asked, people usually say “very little,” unless they can make money off it or need to spend money to get the rock out of their way.

That’s all well and good, but it’s not the only possible answer.

Stromatolites worked it out a long time ago and have stayed with success ever since. (Image: Pat Scullion, CC BY-ND-NC 2.0)

Sometimes we get curious enough to poke around and discover part of the history of life on Earth, hidden in that rock.

With the right motivation, anyone can see it — even me.

The last post closed with an image that often comes to mind when someone mentions geologic time: the Grand Canyon in Arizona. I was going to start out this post with the canyon but then remembered my own first encounter with Earth time, in upstate New York.

Personal experiences are always better than a vacation video.

A good teacher shows instead of telling

My reason to look closely at the Earth was the need to pass an undergraduate geology course back in the Eighties, and like the rest of the class, having first been psyched out for it by a mildly sadistic but rather likable instructor who was also a prominent sedimentologist.

When he said “Go!,” you went, never dreaming of refusal, though he wasn’t nasty or overbearing about it.

He was just one of these people who give orders, expecting to be obeyed, and are obeyed surprisingly often, especially by young people.

Maybe we went along with it not only because of some sense of retaliatory doom if we said no (though nothing ever happened and punishment wasn’t even implied), but also — and this is the main reason — because we always found something interesting after getting to where he had ordered us.

No, we weren’t at the cliff section, but the hill we worked on was about as steep as this lower section. (Image: Doug Kerr, CC BY-SA 2.0)

One day he took us on a field trip to Thacher Park, a scenic nature preserve just south of Albany, New York, where the university is.

Field trips are why many undergrads fill their required science credits with a geology course. They’re fun, they get us outside, and they offer the chance to hear an expert talk about weird-looking rock formations that we’ve all seen in roadcuts and other places but can only wonder about as we pass by.

That day, we didn’t know that Dr. ____ had no intention of explaining the pretty rocks in Thacher Park to us, after having described in the classroom how waterborne particles and biological remains slowly fall to the bottom of a sea — sorting themselves by size and weight along the way — and then harden over time into limestone, mudstone, and other sedimentary rocks.

Ordovician worm trails and ancient debris on a slice of mudstone that’s used to decorate retaining walls at the New York State Museum.

Instead, as we tumbled out the van, proudly brandishing field notebooks whose shiny new yellow covers matched some of the autumn foliage in the parking lot, he gave each of us a hand lens and a compass.

Then he divided us into teams, gave each team a long measuring rod marked off in feet and inches, and told us to climb down the reasonably safe but steeply inclined hillside just beyond parking lot, a hundred vertical feet or so, and come back up while filling our notebooks with measurements of outcrop elevations and detailed descriptions of the particles that composed each limestone bed along the way AND that bed’s relationship to all the others on our route.

We went.

It was fun on the way down. “We’ve got permission to climb fences and explore Thacher Park. Whoo-hoo!”

Coming up was the challenging part.

There were many limestone outcrops, some of them very different from others when you looked closely at the grains with the hand lens, as we had to or else tell Dr. ___ why not when we finally got back to the parking lot.

Nobody wanted to tell him they hadn’t done it.

Crinoid fossils in Kentucky. (Image: James St. John, via Wikimedia, CC BY-SA 2.0)

At least there were a few fossils in there to liven it up: mainly those little white ring fragments left by crinoids, the “sea lilies” of ancient days.

While standing at a 45-degree-plus angle on this hill, sweating on a hot September afternoon and struggling to catch every possible detail in each rocky outcrop, we also tried to draw accurate maps of each site in our notebook, using data from our compasses and the measuring rod.

It took a couple of hours of human time for us to pass through and study the evidence left behind by the passage of hundreds of millions of years of Earth time.

All this plate tectonics stuff was going on over that span of geologic time. Can you spot upstate New York during the Devonian? Me neither.

Our notebooks were well used and dirty by the time we got back to that wonderfully cool and clean twentieth-century parking lot.

Dr. ___ had wisely made himself scarce for a while. As we sat around catching our breaths, two main schools of thought developed: (1) Wow! and (2) I Am Never Going To Take Another Geology Course.

As a geology major and with two years of Adirondack forestry training under my belt, I was already in the first group, as well as a little more used to field work, though I’d never done anything that tough before.

Geology was hard!

Did I really want to do this as a career?

I just didn’t know.

A few minutes later, I noticed one of the stone supports along the parking lot’s edge.

Crinoids are still around. (Image: Alexander Vasenin, via Wikimedia, CC BY-SA 3.0)

It was a chunk of Thatcher Park limestone, but I saw it with new eyes now. Sure, that’s a cliche, but this really happened.

It wasn’t just rock to me now. It was a freeze-frame in GeoTV.

I saw a crinoid at the bottom of the sea being tossed around by swirling mud, dying or already dead. And it was happening before my eyes, though the event itself had occurred so long ago that what is now Thacher Park had been underwater, right at the brink of a continental shelf.

Probably that hapless “sea lily” had gotten caught in one of the great mudslides that happen along continental shelves (sometimes disastrously for nearby land dwellers).

This particular slide had stopped while the crinoid remains were still suspended in mud and then everything hardened into limestone and a type of sedimentary rock that carries the delightful name of greywacke: “gray-wacky.”

Some 400 million years later, a human being came along, cut out a chunk, shaping it into a pillar, and finally I got to see, for a moment, life and geology intertwined.


So I stayed in earth science (though had to give it up a year later after discovering that, no matter how hard I studied, I could not “get” petrology — a VERY important part — well enough to say cool things like this).

Now I’m retired from a different career and face the challenge of describing geologic time to people who just want to know where cats come from.

Back to the sports analogy

Cats are from more than 20 million years ago, and let’s face it — that doesn’t mean a thing to most of us. It’s too much time to really feel.

So let’s turn our cat loose during a game again.

Set the long white field lines 1 mega-annum (Ma) apart instead of a yard.

This term “Ma” means one million years, so the playing field we are imagining is also a calendar of sorts.

We’re standing at the goal line today, and fossils do show that Proailurus, the Dawn Cat, popped into the game around the 27-Ma line. (Werdelin et al)

Just for reference, here are some other events you might have heard of:

  • Nonavian dinosaurs like T. rex, and several other players, left the game midway between the 70- and 60-Ma lines during the K/T extinction.
  • That poor little crinoid we met up above in Thatcher Park got caught by an underwater mudslide waaay down the field somewhere around the 400-Ma line.
  • Ice Age sabercats? Homotherium fossils first show up at around the 4-Ma line, while Smilodon fossils jump in a bit closer to the goal end of the field but still between the 3- and 4-Ma lines.
  • And us? Get out your hand lens.

    There are a thousand kilo-annums (Ka) between our current position on the goal line and the 1-Ma line. Those are the short white lines.

    Depending on which source you check, H. sapiens fossils come in somewhere between 100 and 300 Ka — in other words, no more than a third of the way down to the 1-Ma mark, tops.

    We’re definitely newbies here.

    But we’re also the only ones on the field who can watch the game and, to some degree, call a few plays.

    optimistic view/Shutterstock

This analogy can be carried to extremes — the other end of the field, for instance, is 4,600 Ma away — but that’s not necessary.

I only want to get you used to this Ma/Ka concept.

It’s helpful to a layperson in getting some perspective, although it isn’t exactly how scientists use these terms.

To them, Ma is just an abbreviation for mega-annum, as Ka is of kilo-annum. Just as you or I might measure out 1 cup of flour, paleontologists measure out 1 Ma of Earth time.

That’s how I understood the terms, too, when I began to read learned discussions of how cats evolved.

But there is just so much time — “deep time,” John McPhee calls it — and so many important events to describe, even if you just stick with the general consensus, avoiding controversies and keeping the scientists’ speculation to a minimum.

At least I had already discovered geologic time — in Thatcher Park and elsewhere over the intervening years, though I never made a career out of it. Meeting up with it again therefore didn’t blow me away.

Instinctively, I worked out that Ma/Ka gridline calendar to put the information those papers and books contained in order, using Ma or Ka incorrectly but accurately as abbreviations, similar to but not the same as things like “BC” or “AD.”

Another thing that kept me going were some intriguing questions about that Dawn Cat:

  • Where did it come from?
  • What was happening in the game at that point?
  • What did this cat bring to the game?
  • Why do the cats of our own time so closely resemble it?

That last point may not seem like much. After all, in the last post we did see that all cats today are much alike under the skin.

It’s a huge question, though. And here’s why.

“Primitive” modern cats

Almost thirty million years of evolution separate Leo and Fluffy from the Dawn Cat, way back in 27 Ma or thereabouts. Why did today’s cats change so little over that time span?

At least one line of cats did evolve dramatically: the sabertooths, which included many more species than just Smilodon and Homotherium, if you go all the way back.

We laypeople still have some leftover 19th-century prejudice against sabercats, thinking them too primitive to survive. (Cope)

“Uh, parlay?” (Image: coluberssymbol, via Wikimedia, CC BY-SA 3.0)

Scientists now know better: saberteeth and the various other sabercat skeletal adaptations are very sophisticated evolutionary developments. (Anton; Kitchener et al.; Turner and Anton; Werdelin et al.)

Not only that, saberteeth must really give players an advantage in this game, since they have evolved in several different animals, not just cats, since first appearing in fossil ancestral mammals down around the 270-Ma line (Anton), shortly before the Permian extinction forced almost everyone off the field for a while.

But our cats today are still built much like the Dawn Cat was. (Anton; Turner and Anton; Werdelin et al.)

Why are they the ones left standing, not the fancy-shmancy group?

That’s not an easy question even for specialists in ancient life.

There are problems with every seemingly simple answer, as we will see in later chapters of this series.

We laypeople can’t even get started on it until we know a few basics about the game.

In brief:

  • This Earth is where cats come from.
  • The game is life, and cats are not the only players.
  • The field is a very restricted one, actually: the known fossil and geological records, which are only seen clearly in a few places on the planet. So there is a built-in bias to our play-by-play coverage, but we’re going to do it anyway: the whole story as we can see it.
  • Hey, the rules have a lot to cover! (Image:erebor mountain/Shutterstock)

  • The rules have always been in force, but the primary ones were first noticed by a monk in the 1800s and rediscovered in 1900, several decades after Western observers like Charles Darwin and Alfred Russel Wallace had begun describing some secondary rules. After some disagreements, some of the best minds on the planet collected those prior viewpoints and blended them into a modern “rulebook” between 1918 and 1931. Unfortunately, these brainiacs wrote mostly in math — while that’s certainly a universal language, we laypeople aren’t fluent in it. Luckily for us, former English major and paleontologist George Gaylord Simpson could understand math and also was able to express the game rules in simple terms, most famously in Tempo and Mode in Evolution, which was published in 1944 by friends and family while he was serving in World War II. (Fitch and Ayala; Simpson)

    Simpson’s book, although almost eighty years old now, still holds up in many ways today, per Fitch and Ayala.

    That’s probably because he addressed core points. Tempo and Mode really helped me understand what I was reading about cat evolution and evolution in general.

    I’m also going to use it because the boffins are back to writing in math again. Simpson was an English major, and it shows.

    The major developments since his time — molecular biology and cladistics — are well covered by other sources using the simple approach we take here.

Right. Let’s start off with the most basic question of all: what is life?

Featured image: Juergen Wallstabe/Shutterstock

Antón, M. 2014. 2013. Sabertooth. Bloomington: Indiana University Press.

Cope, E. D. 1880. On the Extinct Cats of America. American Naturalist. xiv (12):833-857.

Fitch, W. M., and Ayala, F. J. 1995. Preface. Tempo and Mode in Evolution: Genetics and Paleontology 50 Years After Simpson. Washington: National Academy Press.

Kitchener, A. C., Van Valkenburgh, B., and Yamaguchi, N. 2010. Felid form and function, in Biology and Conservation of Wild Felids, ed. D. W. Macdonald and A. J. Loveridge, 83-106. Oxford: Oxford University Press, Oxford.

Simpson, G. G. 1944. Tempo and Mode in Evolution. New York: Columbia University Press.

Turner, A., and M. Antón. 1997. The Big Cats and Their Fossil Relatives: An Illustrated Guide to Their Evolution and Natural History. New York: Columbia University Press.

Werdelin, L.; Yamaguchi, N.; Johnson, W. E.; and O’Brien, S. J.. 2010. Phylogeny and evolution of cats (Felidae), in Biology and Conservation of Wild Felids, eds. Macdonald, D. W., and Loveridge, A. J., 59-82. Oxford: Oxford University Press.

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