Sciency Words: Preservation Bias

Hello, friends!  Welcome back to Sciency Words, a special series here on Planet Pailly where we take a closer look at interesting and new scientific terms in order to expand our scientific vocabularies together!  Today’s Sciency Word is:


So is there life on Mars?  Well, there could be.  It’s not totally impossible.  But as I’ve said before on this blog, I think the odds of us finding living things on Mars are pretty low.  The odds of us finding dead things on Mars, however… I think those odds are much better!

Or at least I did think that until I read this paper, entitled “A Field Guide to Finding Fossils on Mars.”  That paper introduced me to the concept of “preservation potential,” and subsequent research led me to learn about something paleontologists call “preservation bias.”

Basically, turning into a fossil isn’t easy.  A lot of factors have to come together just right in order for a dead organism to become preserved in the fossil record.  As that Martian fossil field guide explains:

On Earth, most organisms fail to fossilize because their remains are physically destroyed, chemically oxidized or dissolved, digested by their own enzymes, or consumed by other organisms.  Fossilization only occurs when processes of preservation outpace degradation.

Preservation bias refers to the fact that certain organisms—or certain parts of certain organisms—stand a better chance of fossilizing than others.  Preservation bias can also refer to the fact that some environments (rivers and lakes, for example) do a better job creating and preserving fossils than others (for example, deserts).

A lot of factors can get involved in this, but as a quick and easy example, think of the dinosaurs.  Dinosaur bones fossilize easily enough.  Other parts of the dinosaur… not so much.  That, my friends, is preservation bias at work, favoring hard tissue, like bone, over soft tissue, like muscle or fat.

Now imagine what would have happened if dinosaurs somehow evolved without bones (that’s a weird concept, I know, but just bear with me a moment).  How much would we know about those boneless dinosaurs today?  Would we know about them at all?  Those hypothetical boneless dinosaurs could have roamed the earth for billions of years and left hardly a trace of evidence for us modern humans to find!

Which brings us back to Mars.  There was a time, very long ago, when Mars was a much warmer and wetter planet than he is today.  It’s possible—no, I’d say it’s probable!—that life of some kind developed on ancient Mars, just as it did on ancient Earth.  But would that ancient Martian life have left us any fossils to find?  Maybe.  Maybe not.  It depends on the various factors involved in preservation bias.

P.S.: Boneless dinosaurs are delicious.

Daily Life with Dinosaurs

Hello, friends!

There’s an important science fact that I wish more people were aware of.  Birds are not merely the descendants of dinosaurs.  According to a taxonomic system called cladistics (also known as phylogenetic systematics), birds are dinosaurs.  To quote this article from DinoBuzz:

Using proper terminology, birds are avian dinosaurs; other dinosaurs are non-avian dinosaurs, and (strange as it may sound) birds are technically considered reptiles.  Overly technical?  Just semantics?  Perhaps, but still good science.

So with that in mind, the following statements are 100% true:

  • I often wake up to the sound of noisy dinosaurs outside my window.
  • I sometimes see dinosaurs swimming in the river near my house.
  • I hate it when dinosaurs poop on my car.
  • I enjoy eating dinosaur meat.  Sometimes I put dinosaur meat on sandwiches or in salads.

Anyway, what sort of experiences have you had with dinosaurs in your daily life?  Please share in the comments!

P.S.: Have you seen those dinosaur-shaped chicken nuggets in the grocery store? They’re cute.  I’m just not convinced that they’re made from 100% real dinosaur meat.

Sciency Words: The Silurian Hypothesis

Sciency Words: (proper noun) a special series here on Planet Pailly focusing on the definitions and etymologies of science or science-related terms.  Today’s Sciency Word is:


I’ve heard several variations on this joke.  Why did the dinosaurs go extinct?  Because they didn’t put enough money into their space program.

But what if that isn’t a joke?  What if the dinosaurs (or some other prehistoric creatures) did establish an advanced civilization right here on Earth millions of years before we came along?  Could such a civilization come and go without leaving any trace for us modern humans to find?  Or could the traces be there for us to see, and we just haven’t recognized them yet?

In 2018, NASA astrobiologists Gavin Schmidt and Adam Frank presented this idea in a formal scientific paper titled “The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record?”  As Schmidt and Frank explain in a footnote:

We name the hypothesis after a 1970 episode of the British science fiction TV series Doctor Who where a long buried race of intelligent reptiles “Silurians” are awakened by an experimental nuclear reactor.  We are not however suggesting that intelligent reptiles actually existed in the Silurian age, nor that experimental nuclear physics is liable to wake them from hibernation.

Schmidt and Frank go on to examine some of the ways human industrial activities have changed this planet, and how those changes are being recorded geologically.  They also examine a few of the oddities and anomalies in the geological record as we currently know it.

To be clear, there is absolutely no definitive evidence that another advanced civilization existed on Earth before our own.  Schmidt and Frank go to great pains to emphasize that they don’t actually believe their own hypothesis to be true.

The Silurian Hypothesis is intended to be more of a thought experiment than anything else.  It’s meant to help us better understand how human civilization is changing this planet, and also (remember Schmidt and Frank are NASA astrobiologists) how alien civilizations might be changing their own worlds.

P.S.: The Silurian Hypothesis is also a wonderful example of how science fiction can inspire real life science.

Sciency Words: How to Name Your Dinosaur

I got a little bit behind on my research this week, so I don’t have anything prepared for this week’s episode of Sciency Words.  However, I recently stumbled upon this video which seems thematically appropriate in relation to the Sciency Words series.

It’s a TED Talk with Jack Horner, the world famous paleontologist who discovered Maiasaura and demonstrated that some dinosaur species did, in fact, take care for their young.  If you remember Alan Grant from the original Jurassic Park, Jack Horner served as the real life inspiration for that character.

The TED Talk is about how dinosaurs get their names and how that naming process has led to some pretty glaring scientific mistakes.

Sciency Words is mainly a series about science, but it’s also about linguistics and the philosophy of language.  Words have power.  They shape our thoughts, and they can change the way we understand and experience the world.  And as Jack Horner’s TED Talk illustrates, if we’re careless about the words we choose to use, then our words can mislead us, and we can end up blinding ourselves to things that should be obvious.

Sciency Words: Dinosaur

Today’s post is part of a special series here on Planet Pailly called Sciency Words.  Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


I did a Sciency Words post on the word dinosaur before, when I participated in last year’s A to Z Challenge, but I never felt satisfied with that post.  For one thing, I missed a golden opportunity to tell you one of the coolest sciency things I’ve learned: dinosaurs are not extinct.

Or rather, to be more technical about it, dinosaurs are or are not extinct depending on how you define the word dinosaur.  You see we have two different systems for classifying life: the traditional Linnaean system and an alternative system called cladistics.

In 1735, Swedish botanist Carl Linnaeus published his book Systema Naturae, introducing the world to his system of binomial nomenclature.  All of a sudden, we humans became Homo sapiens, our cats became Felis catus, and so forth.  But under Linnaeus’s system, plants and animals (and also minerals) had to be classified purely according to their physical characteristics, not their evolutionary heritage.  Darwin’s On the Origin of Species wouldn’t be published for another 124 years.

Then in the 1950’s, German entomologist Willi Hennig introduced a new and improved system which he called phylogenetic systematics, but which has since been renamed cladistics.  A “clade,” in cladistics, is a group of animals that share a common ancestor, and if one animal is part of any given clade, then all of that animal’s descendents are part of that clade too, according to Hennig’s system.

Both of these systems are still in use today.  As this article from Ask a Biologist explains, “[Claudistics] is useful for understanding the relationships between animals, while the Linnaean system is more useful for understanding how animals live.”

So because birds evolved from dinosaurs, birds are dinosaurs, claudistically speaking.  Birds are like a subcategory of dinosaur.  And thus the dinosaurs are still here, strutting and flapping about on this planet.

Sciency Words: Thagomizer (An A to Z Challenge Post)

Today’s post is a special A to Z Challenge edition of Sciency Words, an ongoing series here on Planet Pailly where we take a look at some interesting science or science related term so we can all expand our scientific vocabularies together. In today’s post, T is for:


Once upon a time, there was a caveman by the name of Thag Simmons. According to Gary Larson’s Far Side comic strip, Thag met an unfortunate end when he was clubbed to death by the spiky tail of a stegosaurus. As a result, cavemen began to call the stegosaur’s spiky tail a thagomizer.

Larson’s thagomizer comic was originally published in 1982. Death by thagomizer may sound like a gruesome way to go, but based on my own research about cavemen/dinosaur interactions, I have reason to believe Thag Simmons had it coming.

Over the course of this Sciency Words: A to Z series, we’ve seen some scientific terms that were pretty clever, and some that were kind of dumb, and a few that are truly misleading. But until now, we haven’t talked about scientific terms that come from pop culture.

In 1993, paleontologist Ken Carpenter was making a presentation about the most complete stegosaurus skeleton ever found, and he needed a term for the dinosaur’s distinctive spiky tail. One of the spikes had apparently broken and healed, which was compelling evidence that stegosaurs really did use their spiky tails as weapons.

In homage to Gary Larson, Carpenter chose the term thagomizer, and the term has now become the proper, semi-official term for that part of stegosaurus anatomy.

I want to thank @breakerofthings for letting me know about this term. I’d originally planned to do something else for T, but I think this was much better. Be sure to check out A Back of the Envelope Calculation, where “breaker” is doing an A to Z Challenge series on materials science in Sci-Fi/Fantasy.

Next time on Sciency Words: A to Z, how do you pronounce Uranus?

Sciency Words: Dinosaur (An A to Z Challenge Post)

Programming note: If you’re here for today’s Insecure Writer’s Support Group post, please click here.

Today’s post is a special A to Z Challenge edition of Sciency Words, an ongoing series here on Planet Pailly where we take a look at some interesting science or science related term so we can all expand our scientific vocabularies together. In today’s post, D is for:


When I was a kid, dimetrodon was my favorite dinosaur. It has a sail on its back. How cool is that?

Then I found out that dimetrodon is not a dinosaur. It’s just a lizard. Then I found out from this video that it’s not even a lizard.

Also, pterodactyls aren’t dinosaurs. Neither are plesiosaurs or ichthyosaurs. None of my favorite dinosaurs were actually dinosaurs! Frustrating, isn’t it?

So today, I thought I’d give you a quick tip on how to tell when a “dinosaur” is actually not a dinosaur. Sciency Words is all about defining scientific terms, and paleontologists use several key features to define what is or isn’t a dinosaur. For example: the number of openings in the skull, the shape of the hip bone, the type of joint at the ankle….

If you’re a professional dinosaur scientist, you need to know this stuff. But for the rest of us, the easiest way to tell (in my opinion) is by looking at the orientation of the legs. Dinosaur legs are vertical to the ground, not horizontal. They go straight up and down, rather than being splayed out to the sides.

So if you think it’s a dinosaur, but the legs are splayed apart, it’s not a dinosaur.

If you’ve ever seen a crocodile or salamander try to run, you can understand why having your legs splayed apart like that is a disadvantage.

Standing upright on their vertical legs, dinosaurs had a much easier time walking and running on land. Also, vertical legs can support more weight, allowing dinosaurs to become much bigger and much heavier than their cousins, the amphibians, reptiles, and whatever the heck dimetrodons were.

Next time on Sciency Words: A to Z Challenge, we’ll find out what our planet’s name is.

Sciency Words: Brontosaurus (An A to Z Challenge Post)

Today’s post is a special A to Z Challenge edition of Sciency Words, an ongoing series here on Planet Pailly where we take a look at some interesting science or science related term so we can all expand our scientific vocabularies together. In today’s post, B is for:


I’ll never forget that sad moment in my childhood when I found out that brontosaurus is not a real dinosaur. Someone made a mistake, and we had to call brontosaurus apatosaurus instead.

Here’s a quick rundown of events in the brontosaur/apatosaur naming controversy:

  • 1877: A dinosaur skeleton is discovered and given the name scientific name (genus and species) Apatosaurus ajax.
  • 1879: Another dinosaur skeleton is discovered and given the name Brontosaurus excelsus.
  • 1903: Upon further examination, it’s determined that these two dinosaur specimens are too closely related and should be classified as the same genus. Since the genus Apatosaurus was identified first, Brontosaurus excelsus became Apatosaurus excelsus.

On a personal note, I was stunned to find out all this happened way back in 1903. When I was a kid, I was under the impression that this was a much more recent development.

Anyway, there’s some good news for brontosaurus fans. In 2015, Brontosaurus was reinstated as its own genus. Turns out that while those two skeletons are very similar, there’s enough of a difference in the structure of the neck to justify classifying them separately.

By the way, brontosaurus means “thunder lizard,” because of the sound it must have made when it walked. Apatosaurus apparently means “deceptive lizard.” I’m not sure why they called it that back in 1877, but after this case of attempted identity theft, I’d say the name fits.

Next time on Sciency Words: A to Z Challenge, we’ll head out into space and meet some centaurs.

Sciency Words: The K-T Event

Sciency Words MATH

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us all expand our scientific vocabularies together. Today’s term is:


You already know this story. It was 65 million years ago. There were dinosaurs, there was an asteroid…

It’s easily the most famous asteroid impact in Earth’s history, and it’s called the K-T Event, or sometimes the K-Pg Event.

In geology shorthand, the letters stand for:

  • K: the Cretaceous period, which is spelled with a K in German. This was the last period of geological history in which dinosaurs roamed the Earth.
  • T: the Tertiary period, which immediately followed the Cretaceous. According to the International Commission on Stratigraphy (ICS), we’re not supposed to use this name anymore, but people still do. It’s sort of like how some people keep calling Pluto a planet, no matter what the International Astronomy Union (IAU) says.
  • Pg: the Paleogene period, which is the period immediately following the Cretaceous according to the ICS’s new list of geological periods. Please note, the Tertiary and Paleogene are not really interchangeable terms. They have the same starting point, but different end points.

Geologists and paleontologists puzzled for decades over a layer of clay separating Cretaceous and Tertiary (or Paleogene) rock. They called it the K-T boundary. There were several competing hypotheses about what might have caused this boundary and how it related to the mass extinction event that killed off the dinosaurs.

Then in 1980, a paper came out entitled “Extraterrestrial Cause for the Cretaceous-Tertiary Extinction.” This paper reported the discovery that the K-T boundary contained abnormally high levels of the element iridium.

Platinum group metals like iridium are extremely rare on Earth (except in the planet’s core) but common in asteroids. So whenever you find lots of iridium in Earth’s crust, you can justifiably assume an asteroid put it there.

The most likely scenario is that a large asteroid, about 10 km in diameter, smashed into Earth, flinging dust and debris high into Earth’s atmosphere. Enough to block out the sun worldwide for several years. This global dust cloud would have included plenty of material from the asteroid itself, which would have been partially vaporized by the heat of the impact.

A major problem with the original 1980 paper was that, at the time, no known impact crater of the appropriate age was sufficiently large. But of course, that was back in 1980. The crater has since been found in the Yucatan Peninsula, and now just about everybody knows the story of the K-T Event (even if they don’t know it’s called that).

P.S.: The K-T Event is not to be confused with the Katie Event. You know, that time your BFF Katie had waaaaay too much to drink and threw a temper tantrum of apocalyptic proportions.

Addendum: While there does seem to be general, widespread consensus that the K-T asteroid impact either caused the extinction of the dinosaurs or contributed significantly to their demise, there is not universal agreement. As Planetary Defense Commander notes in the comments, there are other possibilities worth considering.