Cody Cassidy tells us How to Survive History and Dinosaurs!

Article | Jan 2024

In CODY CASSIDY’s book, How to Survive History, he provides us with tan often humorous and informative guide to surviving history’s most challenging threats. From meteors big enough to sterilise the planet to famines to pandemics, from tornadoes to the Chicxulub asteroid, the odds of human survival are slim but not zero – at least, not if you know where to go and what to do.

In this extract we learn how we might be able to outrun the dinosaurs, so as to avoid being eaten.



Let’s say you want to visit the era when the most powerful predators in history attacked the largest land animals the planet has ever seen. You want to see 80‑ton reptiles, carnivores with jaws comparable to a car shredder, and an animal the size of a giraffe take flight

So you travel back 70 million years to the Mesozoic era – back to the Dinosaur Age. In the warmed climate, you’ll feel the sticky heat of the Louisiana bayous as far north as Montana. You’ll notice the changed geography:the absence of Rocky Mountains and the Sierra Nevada, the sea covering the midwestern United States, the island of India.

Grass will have only recently evolved. So you’ll see a few blades, but no grasslands – only ferns, ficus, figs, cycads, and ginkgoes, along with large trees and dense forests. You’ll also see the famous Tyrannosaurus rex.

Unfortunately, it will see you too.

You might think your only chance would be to hide, stand still, play dead, or climb. But surprisingly – shockingly – recent evidence suggests that you might be able to run from the most powerful predator to ever walk this planet.

At least, if you know how to use your biggest advantage: your size.



If a mouse fell down a 1,000‑foot mine shaft, the renowned evolutionary biologist J B S Haldane once proposed, the mouse would rise, shake the dust off, scurry away, and maybe even get right back up to do it again. If a rat fell from the same height, however, it would die. A horse would splash, Haldane writes, and a human would break.

Haldane does not provide a colourful verb in his 1926 essay On Being the Right Size for what would occur if a nine‑ton Tyrannosaurus rex fell into that mine. But the giant predator would scream down the shaft at 172 miles per hour, hit the ground with 120 tons of force, and  …  shatter? Dismember? Detonate? Erupt?

Regardless of the proper descriptor for the T. rex’s disturbing demise, the purpose of Haldane’s gruesome thought experiment was to demonstrate the dramatically different relationships that large and small animals have with gravity. This relationship, and the differing fates of the mouse and the rat, are explained by the ‘square‑cube law’, which states the simple fact that, as an object expands, its volume cubes while its surface area merely squares. Because a falling animal’s surface area increases its air resistance while its mass determines the force of its impact, the falls of various animals can be thrilling, tragic, or messy, depending on small differences in size. This may be a simple concept, but because a cubed number grows so much faster than a squared one, it is exceedingly difficult to intuit what the effects of small differences in size will be. That’s particularly true with regard to the largest land animals to have ever walked the earth, especially if you have to outrun them.

When the T‑Rex takes an interest in you, you may see its long legs and powerful muscles and think you should hide. Don’t. You have the disproportionate effects of size on your side. The T‑Rex’s eruptive demise at the bottom of the mine shaft illustrates the most important factor to consider when facing this giant saurian’s pursuit. In the run for your life, its awe‑inspiring, terrifying, stu‑ pefying size would be, in fact, your greatest advantage.



A full‑grown Tyrannosaurus rex was absurdly huge and absurdly powerful. It had rows of teeth it could push through triceratops bone. It could toss human‑sized chunks of meat sixteen feet into the air with its jaws. It was as tall as a giraffe and, at nine tons, as heavy as an elephant. ‘Tyrannosaurus rex had proportionally more muscles devoted to its movement than nearly any animal that’s ever lived,’ says Eric Snively, a biologist at Oklahoma State University who studies the biomechanics of dinosaurs. And yet if you see one, you should be only mildly concerned, because a tyrannosaur couldn’t run.

I asked John R Hutchinson, lead author of a 2002 paper published in Nature titled ‘Tyrannosaurus Was Not a Fast Runner’, what a tyrannosaurus’s performance in a race would look like. ‘A short‑distance jog is about thebest we’d expect,’ he said. ‘And not with a fast start, either.’

The incredibly powerful, long‑legged tyrannosaurus was slow for the same mathematical reason its demise in the mine shaft would be so eruptive. Like surface area, bone strength only squares as volume cubes. The result is that, as an animal increases in size, it requires proportionally more muscle and leg bone to stand, move, and run. Beyond a certain size, running becomes physically impossible, which is why giants and King Kong only exist in fairy tales. For all its muscular bulk, the Tyrannosaurus rex’s leg bones would have shattered under anything more than the stress of a brisk walk. Judging by its mass, muscle, and bones, Snively doesn’t believe an adult tyrannosaurus could have moved faster than 12 or 13 miles per hour. Though 12 miles per hour approaches the top speed of a typical human depending on their conditioning – it equates to a twenty‑second 100‑meter dash – the T. rex’s slow acceleration would give the average runner a good chance of out‑ sprinting or out maneuvering the lumbering predator.*

Of course, the Tyrannosaurus rex would hardly be your only concern in the Mesozoic era. Numerous other meat‑eating dinosaurs of various sizes might take an interest in snacking on you. Once again, whether you could outrun them or not depends on their weight.

In 2017, biologist Myriam Hirt and colleagues, studying animal movement at the German Centre for Integrative Biodiversity Research, asked a simple question: Is there an optimum size for speed? And the surprisingly simple answer, they discovered, is yes. When Hirt plotted the weight and speed of every running, swimming, and flying animal on earth, she found that, regardless of mode of movement, size and speed follow a parabolic curve. Both the smallest and the largest animals are the slowest. She concluded that if you were designing an animal for speed, it should weigh approximately 200 pounds. A bit heavier for a swimmer, a bit lighter for a flyer.

Hirt’s discovery not only suggests that you should fear the mid‑sized dinosaurs most, but, perhaps even more important, that you don’t need to fear the largest at all. Regardless of strength or design, it would be physically impossible for the largest dinosaurs to outrun a human in good physical condition. The reason, Hirt tells me, is a result of the interplay between power, acceleration, and the metabolism that fuels both.

*Admittedly, there is some concerning speculation that T. rex hunted in packs, which would complicate your escape. Thankfully, the best current evidence suggests that, though they may have killed in packs like crocodiles, they did not coordinate their pursuits like wolves.

How to Survive History by Cody CassidyAn animal’s top speed is the meeting point of two factors. The first is its total muscle power, which scales proportionally with its mass. The second is its ability to accelerate that mass, which does not scale proportionally. Acceleration relies on anaerobic muscle, which uses a stored fuel called ATP to power its rapid contractions. These so‑called fast‑twitch muscles produce the rapid, powerful contractions needed for acceleration. But ATP capacity is finite, it quickly depletes, and its capacity is determined by metabolism.

For reasons that aren’t totally understood, an animal’s energy production – metabolism – decreases proportionally to its mass (more precisely, it decreases to the power of 0.75). This reduction makes larger animals more energy efficient than smaller ones. If humans had a metabolism proportional to that of a mouse, for example, we would have to eat around 25 pounds of food per day. Larger animals are thus more efficient, but the cost of this efficiency is proportionally less ATP energy to accelerate.

By creating a simple formula that represents the balance between strength and acceleration, Hirt predicted the speeds of animals based upon nothing but their weight.

That would give you some possibility of escape. But there is a chance it ran more like a cheetah. In which case … good luck.

Thanks to the limits of metabolism and mass, we can eliminate every dinosaur weighing more than 6,000 pounds as a predatory threat. There is likely no animal of that size or larger – neither today, nor at any point in history – that a young, well‑conditioned human couldn’t outrun.

Unfortunately, there are numerous predatory threats that weigh substantially less. Hirt’s discovery reveals a speed limit on the largest dinosaurs, but beneath that limit an animal’s size is not the only determinant for its speed. Clearly, two species of roughly the same weight – such as, say, the human and the cheetah – can run at dramatically different speeds depending on their body design.

So before you lace up your running shoes, you need to know the precise speed of your foe. You need to know if you’re betting your life on a race against a reptilian roadrunner.

But how does one determine the precise speed of an extinct species based upon nothing but bones and a few fossilised footprints?

Fortunately, in 1976 British zoologist Robert McNeill Alexander made the remarkable observation that all animals – from ferrets to rhinos – run with a ‘dynamically similar’ gait. ‘Dynamic similarity’ is an engineering term used to refer to motions that can be made the same simply by changing their scale – like swinging pendulums of different sizes. Alexander’s discovery enabled paleontologists to estimate a dinosaur’s running speed based on nothing but its hip height and stride length for the same reason the swinging frequency of a pendulum can be predicted by knowing only its length and swing angle.

Unfortunately, it’s no more than a rough formula with the possibility of serious error, Hutchinson tells me. For example, Alexander’s formula suggests that the carnivorous three‑ton Albertosaurus ran 22 miles per hour. That would give you some possibility of escape. But there is a chance it ran more like a cheetah. In which case … good luck.

In 2020, the paleontologist Alexander Dececchi combined Hirt’s and Alexander’s formulas, along with recent archaeological discoveries of dinosaur fossils, to estimate the speeds of 71 different dinosaurs. And though there are too many medium‑sized, fast, and dangerous carnivores to make a complete compendium, we can look at a few species as examples. If the dinosaur you see has similar body dimensions to one shown below, expect a comparable athletic performance.

Note: Obviously, your level of concern should vary depending on your running speed. To determine mine,I used a simple formula* and found I can sprint around 15 miles per hour. I would suggest you do the same. But as a rough guide to human speed: A gold‑medal contender in the 100‑metre dash can run 27 miles per hour, a good high school sprinter might run 22, the average person like myself could hope to reach 15 given proper motivation, and a brisk jog is around 7.

*Use this formula to estimate your speed if you don’t have an easier electronic method handy: Pace out 60 metres and 100 metres, then time how quickly you can run both distances. Divide 40 by the difference. So, 40 metres ÷ (your 100 metre time minus your 60 metre time) = your top speed in metres per second. 1 m/s = 2.2 mph.

Unless you’re in contention for a gold medal or are, at the very least, a fast amateur sprinter, each of these dinosaurs will athletically outclass you. Still, all is not lost if one should attack. Studies of the chases between cheetahs and impalas and between lions and zebras prove that a prey animal like you has a few significant advantages.

Alan Wilson, a professor at the Royal Veterinary College at the University of London who studies locomotor biomechanics, attached accelerometers to these predators and their prey to calculate their exact speed, agility, and tactics – and came away with encouraging results. His measurements suggest the cheetah is capable of running at least 53 miles per hour, while its prey, the impala, tops out at a mere 40. Likewise, the lion can reach 46 miles per hour, while the zebra can run only 31. Despite their significant speed deficit, both the impala and the zebra successfully escape in two out of every three pursuits. And even though a lion runs slightly faster than an impala, it won’t even attempt to chase one in an open field.

Wilson’s findings suggest that a pursuing dinosaur should not be able to catch you unless it is significantly faster.

But that’s if you know how to run. If you merely flee at top speed from these reptiles, the only way you’ll exit the Mesozoic era is as a coprolite.* Instead, to successfully escape a more ath‑ letic pursuer, you have to run smart. You have to use tactics. And above all, you must be unpredictable.

*Fossilised dinosaur poop.


Internal 1 How to Survive



Internal 2 How to Survive



Internal 3 How to Survive





When Wilson’s accelerometer measured the speeds of impalas fleeing from cheetahs, he discovered that even though they are capable of a blistering 40 miles per hour, in a race for their life they almost never ran faster than 31. The explanation for this surprising result, his study concludes, is that, at top speed, an animal sacrifices maneuverability. Their turning angles widen and thus their trajectory becomes predictable. Obviously, if a fasterpursuer knows where you’re going, you’re dead.

When Wilson plugged in the athletic parameters of predator and prey into a computer model and ransimulations, he found two tactics that those being chased should employ. First, when the dinosaur begins chasing you but is still far away, change course fre‑ quently but do not decelerate. Second, when the predator draws within two or three strides, rapidly decelerate, turn sharply, and accelerate. Time this maneuver correctly and yourpursuer’s faster speed will result in a wider turn and a loss of a stride or two off the pace. When it catches up, do it again.

Your goal is to buy time. You have an endurance advantage. Recent studies like Dececchi’s suggest some dinosaur species may have possessed remarkable endurance for their size – but your springy hips, stretchy Achilles tendons, and efficient cooling sys tems make you one of the greatest endurance runners nature has ever created. The longer the race, the greater your chances.

At some unfortunate point, however, the athletic disparity breaches a certain threshold, and no amount of correctly timed turns will be enough. That will likely be the case should you find yourself against what Snively tells me would be your most dangerous purser – the same Tyrannosaurus rex we’ve already dismissed, but with one significant difference. It’s not the biggest, full‑grown T‑Rexes you should fear, says Snively.

It’s the juveniles.


Tyrannosaurus (juvenile) Top speed: 33 miles per hour



Unlike most animals, a tyrannosaurus is not its fastest as an adult. Instead, it reaches its peak speed in its youth, before it’s slowed by its immense bulk. A teenage Tyrannosaurus rex runs an estimated 33 miles per hour, because it weighs a relatively lithe 2,000 pounds and yet already possesses jaws strong enough to tear through your bones. The young T‑Rex is more likely to attack as well, because, unlike an adult, which hunts 7,000‑pound duck‑ bill dinosaurs and five‑ton triceratops, a teenage tyrannosaurus probably eats animals of your size.

If a young T‑Rex attacks, then you’ll have to resort to more de‑ vious tactics to survive (unless you’re an Olympic sprinter – in which case you stand an impala‑like chance of escape). You’ll need the luck of a small caveto squeeze into or a thick bramble in which you can dive headlong. Or you can make your own luck by running the tyrannosaurus into a trap. Try laying a blanket of brush over a watering hole, a pit lined with stakes, or, if you prefer an eruptive result, over a very deep mine shaft.



Cody Cassidy author Cody Cassidy is a freelance writer, editor, University of Oregon journalism major living in San Francisco who, when not slipping on banana peels, spends his time playing ultimate frisbee, surfing, and going on factory tours thinking about what would happen if he fell into the potatoes.


Follow Cody Cassidy in Instagram

Author: Cody Cassidy

Category: Humanities

Book Format: Paperback / softback

Publisher: Bedford Square Publishers

ISBN: 9781835010372

RRP: $24.99

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