What is Impossible in Evolution? Was ist in der Evolution nicht möglich? ¿Qué es imposible en la evolución? Qu'est-ce qui est impossible dans l'évolution ? 進化において不可能なことは何か？ 진화에서 불가능이란 무엇인가요? Kas neįmanoma evoliucijoje? Wat is onmogelijk in evolutie? O que é impossível na evolução? Что невозможно в эволюции? Evrimde İmkansız Olan Nedir? Що неможливого в еволюції? 進化論中有什麼是不可能的？

Why don't we see certain traits in nature? Warum sehen wir bestimmte Merkmale nicht in der Natur?

If evolution is so innovative, if it's powerful enough to create this and this and this and

whatever this is, etc… then…

Why can't humans grow wings and take to the sky? Warum können den Menschen keine Flügel wachsen und sie sich in den Himmel erheben?

Or why don't fish have propellers?

Why are there no 5-legged cats or giraffe-sized chickens?

Why do no animals have wheels? ¿Por qué ningún animal tiene ruedas?

And why haven't zebras evolved machine guns to fight off lions?

Today, instead of talking about incredible, mind-blowing traits that evolution has created, Heute sprechen wir nicht mehr über die unglaublichen, verblüffenden Eigenschaften, die die Evolution hervorgebracht hat,

like we've done so many times before, we're going to talk about the limits of evolution's

creativity, and why certain traits are impossible to evolve.

There is a myth in evolution that nature is infinitely creative.

It isn't.

Probably.

By considering the reasons why certain things can't evolve we can learn a lot about how

evolution actually does work.

So yes, while these would all be awesome… Así que sí, aunque todo esto sería genial...

I don't make the rules, evolution does.

… stupid evolution.

I want a tank zebra. Ich möchte ein Panzerzebra. Quiero una cebra tanque.

We begin in my childhood nightmares.

The 1985 film Return To Oz was one of the most terrifying films I ever accidentally La película de 1985 Regreso a Oz fue una de las más terroríficas que he visto accidentalmente.

flipped the channel to as a young nerd. cuando era un joven empollón.

This unofficial sequel to the 1939 film The Wizard of Oz provided the fodder for more Diese inoffizielle Fortsetzung des Films "Der Zauberer von Oz" von 1939 lieferte das Futter für mehr Esta secuela no oficial de la película de 1939 El mago de Oz dio pie a más

than one nightmare thanks in large part to these: The Wheelers. mehr als nur einen Albtraum, was zum großen Teil auf diese zurückzuführen ist: Die Wheelers. dan één nachtmerrie grotendeels dankzij deze: The Wheelers.

There is something deeply unnatural about a creature with wheels instead of hands or

feet.

Both because it's extremely creepy, and because it's biologically impossible.

The wheeled animal question is a canonical case study when it comes to impossible things La cuestión del animal con ruedas es un caso de estudio canónico cuando se trata de cosas imposibles

in evolution, or “forbidden phenotypes”. in evolutie, of "verboden fenotypes".

And remember, a phenotype is the observable physical properties of an organism. Und denken Sie daran, dass ein Phänotyp die beobachtbaren physischen Eigenschaften eines Organismus ist.

There are organisms that roll up their entire bodies to enable wheel-like rolling movement, Es gibt Organismen, die ihren gesamten Körper aufrollen, um eine radähnliche Rollbewegung zu ermöglichen, Hay organismos que enrollan todo su cuerpo para poder desplazarse rodando como una rueda,

like pangolins, spiders, tumbleweeds, and roly-polies… or whatever you call these wie Schuppentiere, Spinnen, Steppenläufer und Krabbeltiere... oder wie immer man diese Dinge nennt como pangolines, arañas, plantas rodadoras, y roly-polies... o como se llamen estos zoals schubdieren, spinnen, tumbleweeds en roly-polies ... of hoe je deze ook noemt як панголіни, павуки, перекотиполе та роллі-полі... або як ви їх називаєте

things where you're from.

Or maybe we could envision an animal rolling around like the mulefa, a fictional species Of misschien kunnen we ons een dier voorstellen dat rondrolt zoals de mulefa, een fictieve soort

in the fantasy series His Dark Materials, which hooks its feet into round seed pods en la serie de fantasía His Dark Materials, que engancha sus pies en vainas redondas de semillas

and uses them as wheels.

But acting like a wheel or using a found object as a wheel is not the same as having wheels Aber sich wie ein Rad zu verhalten oder einen gefundenen Gegenstand als Rad zu benutzen, ist nicht dasselbe wie Räder zu haben.

as body parts.

No animal uses a rolling wheel body part to move its body.

And some of the reasons why are pretty obvious: A structure capable of rolling continuously

around an axle would be physically separated from the body and therefore impossible to

build in a developing animal.

This would also make it impossible to deliver nutrients and blood or nerve impulses to the

wheeled appendage as well.

But there are other less-obvious reasons animals don't have wheels.

Which brings us here.

To a Bronze Age foot soldier, the most terrifying sight imaginable would've been enemy chariots Para un soldado de a pie de la Edad de Bronce, el espectáculo más aterrador imaginable eran los carros enemigos. Voor een voetsoldaat uit de Bronstijd zouden vijandelijke strijdwagens het meest angstaanjagende gezicht zijn geweest

rolling onto the battlefield.

Manned by a driver and either an archer or javelin thrower, the ability of these horse-drawn

wheeled vehicles to move quickly across the field of battle made the chariot the dominant vehículos con ruedas para desplazarse rápidamente por el campo de batalla convirtieron al carro en el dominante

shock and awe weapon of its time from Mesopotamia to the Mediterranean. arma de choque y pavor de su época desde Mesopotamia hasta el Mediterráneo.

But by the 6th century AD, the chariot, along with almost every other wheeled form of transportation, Pero en el siglo VI d.C., el carro, junto con casi todas las demás formas de transporte con ruedas,

had basically disappeared between North Africa to Central Asia.

How could such a seemingly dominant technology vanish?

Because wheels had been replaced by camels.

This happened for several reasons: The roads originally laid down across the Roman empire

had deteriorated.

The skill and craftsmanship required to make efficient wagons and carts had been slowly Die für die Herstellung effizienter Wagen und Karren erforderliche Geschicklichkeit und Handwerkskunst wurde langsam

forgotten.

But most simply, in this particular region camels were just better and more efficient

than wheels when it came to carrying stuff. que las ruedas a la hora de transportar cosas.

The camel can travel farther, with less food and water than a horse or ox.

They can cross rivers and rough terrain easier than a wheeled cart, and where a wagon requires

a person to tend every two animals or so, half a dozen fully loaded camels could be una persona para atender cada dos animales más o menos, media docena de camellos completamente cargados podrían ser

managed by one person.

Likewise, Europeans were stunned to find no wheeled vehicles used by the Aztecs, Incas, Del mismo modo, los europeos se quedaron atónitos al no encontrar vehículos de ruedas utilizados por los aztecas, incas,

and other American indigenous cultures, even in places where llamas were used as pack animals.

Archaeological discoveries show us early American cultures definitely invented wheels

of their own, but beyond water wheels for milling, or toys, they didn't find wheels aber abgesehen von Wasserrädern zum Fräsen oder Spielzeug haben sie keine Räder gefunden. propias, pero más allá de las ruedas hidráulicas para moler, o los juguetes, no encontraron ruedas

all that useful or necessary for their particular terrain and environment. für ihr spezielles Terrain und ihre Umgebung nicht so nützlich oder notwendig sind. tan útiles o necesarios para su terreno y entorno particulares.

And this is how chariots and camels and creepy Wizard of Oz sequels relate to evolution: Y así es como los carros y los camellos y las espeluznantes secuelas del Mago de Oz se relacionan con la evolución:

Biological or cultural adaptations depend on the environment in which they arise.

The best solution to a problem depends on the problem. Die beste Lösung für ein Problem hängt von der Art des Problems ab.

While propellers and spinning blades are an optimal way to move human-made craft through Propeller und sich drehende Blätter sind zwar ein optimales Mittel, um von Menschen gebaute Fahrzeuge durch Mientras que las hélices y las palas giratorias son una forma óptima de mover las embarcaciones humanas a través de

the water, the fins of fish are actually more efficient at providing propulsion in most

cases.

So, there's no fish with propellers, and because we haven't been able to match evolution's Por lo tanto, no hay peces con hélices, y porque no hemos sido capaces de igualar la evolución de la

aquatic creativity, we don't have boats powered by big tail fins. creatividad acuática, no tenemos barcos propulsados por grandes aletas de cola.

Likewise, the wheel, as a technology, isn't intrinsically better or more advanced than

other ways of moving.

The wheel only dominated in certain environments, under certain conditions.

And even if animals were capable of growing wheels as body parts, in most environments

and terrains they would probably work worse than feet or hooves. y terrenos probablemente funcionarían peor que los pies o las pezuñas.

Which brings us to a different kind of terrain altogether… the fitness landscape. Das bringt uns zu einem ganz anderen Terrain: der Fitnesslandschaft. Lo que nos lleva a un terreno totalmente distinto... el paisaje del fitness.

Here I don't mean fitness like your ability to run a mile or do pushups.

In biology, fitness is essentially a score that represents a trait's ability to survive In der Biologie ist die Fitness im Wesentlichen ein Wert, der die Fähigkeit eines Merkmals zum Überleben darstellt. En biología, la aptitud es esencialmente una puntuación que representa la capacidad de un rasgo para sobrevivir In de biologie is fitness in wezen een score die het vermogen van een eigenschap om te overleven weergeeft

and reproduce.

The wings of birds, bats and even pterosaurs, are all modified structures of the arm, hand,

and fingers.

They are an example of convergent evolution, where organisms that aren't that closely

related evolve similar features or phenotypes. relacionados evolucionan hacia características o fenotipos similares.

You have to go pretty far back to find the common ancestor between these winged creatures, Hay que remontarse muy atrás para encontrar el antepasado común de estas criaturas aladas,

but the wings of birds, bats, and pterosaurs are all descended from an arm that is built

essentially the same as yours or mine.

One bone up here, two bones here, lots of little bones here and long bones here.

So theoretically, humans could evolve wings, right?

Actually, no.

When a trait evolves, every stage of its evolution pretty much has to provide an advantage, or

at least not be harmful.

Even if the final trait, like humans flying with wings, would be super cool and give us

lots of new advantages, we would have to be able to get from this to wings in a way that muchas ventajas nuevas, tendríamos que ser capaces de llegar de esto a las alas de una manera que

every step is beneficial.

You can't evolve anything that reduces your fitness.

A fitness landscape is a way to look at a lot of different variations and how they score Un paisaje de fitness es una forma de ver muchas variaciones diferentes y cómo puntúan

versus one another. unos contra otros.

Each square represents a variation or genetic possibility.

The closer the squares, the more similar two variations are, and the further the squares,

the more different they are.

The fitness of each genetic possibility is represented by its height on the landscape.

Here's the problem.

You can only ever move uphill, toward higher fitness. Es kann immer nur bergauf gehen, hin zu mehr Fitness.

There may be a highest peak, with the best trait, on your landscape but you can't get

there because you'd have to travel down into a valley first.

Evolution is walking around this landscape blind, it doesn't plan or have foresight, La evolución camina a ciegas por este paisaje, no planifica ni tiene previsión,

so organisms often get stuck on top of these little hills, called local optima. dus organismen komen vaak vast te zitten bovenop deze kleine heuvels, lokale optima genaamd.

They're as good as they can be without getting worse.

The human eye is a perfect example of a local optimum.

If the optic nerve and the eye's blood vessels ran behind the eye instead of through it, Wenn der Sehnerv und die Blutgefäße des Auges hinter dem Auge und nicht durch das Auge verlaufen würden, Si el nervio óptico y los vasos sanguíneos del ojo discurrieran por detrás del ojo en lugar de a través de él,

we wouldn't have a blind spot in our vision.

This is how octopus eyes are built and it's a much better way to make an eye. So werden Krakenaugen gebaut, und es ist eine viel bessere Art, ein Auge herzustellen.

But we can't jump all the way to that higher fitness peak, or travel through a valley where

we'd make our eyes worse in the meantime.

Likewise, if we wanted to have wings like birds, each stage of our evolution from arms

to wings would have to provide a benefit.

When the first birds were evolving from raptor-like dinosaurs, they already had feathers for attracting

mates.

So they could use them to glide like flying squirrels—that's a fitness advantage. So konnten sie wie fliegende Eichhörnchen gleiten - das ist ein Fitnessvorteil.

And each tweak and variation would help them glide farther—more fitness improvements—all

the way to powered flight… at the top of a fitness hill. el camino hacia el vuelo propulsado... en la cima de una colina de fitness.

For humans, variations in our hands or arms that gave us a small amount of gliding ability

wouldn't really improve our fitness right away.

But having dumb wing hands would have a lot of costs when it came to things like using Aber stumme Flügelhände zu haben, würde eine Menge Kosten verursachen, wenn es darum geht, Dinge wie

tools.

So even if being able to truly fly would be a huge improvement overall, those intermediate

steps can't evolve if they mean moving down the fitness hill. los pasos no pueden evolucionar si significan bajar la colina del fitness.

And this is why zebras don't have laser turrets.

Zebras would clearly benefit from evolving defensive laser weapons to keep lions away,

but they can't because the intermediate steps of evolution have to be helpful or at aber sie können es nicht, weil die Zwischenschritte der Evolution hilfreich sein müssen oder bei

least not harmful. zumindest nicht schädlich.

A laser turret or machine gun or bazooka is only useful when it is complete.

The intermediate, functionless laser organ would just be hogging vital nutrients, a fitness Das zwischengeschaltete, funktionslose Laserorgan würde nur lebenswichtige Nährstoffe verschlingen, eine Fitness El órgano láser intermedio, sin función, sólo estaría acaparando nutrientes vitales, una aptitud Het tussenliggende, functieloze laserorgaan zou alleen maar essentiële voedingsstoffen binnenkrijgen, een fitness

loss.

And sure, projectile weapons have evolved in other animals.

Like archerfish that hunt by spitting water, or antlions that use sand as a projectile Como los peces arqueros, que cazan escupiendo agua, o los hormigueros, que utilizan la arena como proyectil. Zoals boogschuttervissen die jagen door water te spuwen, of mierenleeuwen die zand als projectiel gebruiken

weapon.

But if you're prey, running away might just work well enough, so you're stuck at a local Pero si eres una presa, huir podría funcionar bastante bien, así que estás atrapado en un local

optimum without laser turrets.

Evolution works like trying to make improvements to an engine while the car is in the middle

of a race.

You can't break your engine in order to make it work better.

Of course, I'm not willing to give up my dream of flying so easily.

Maybe there's another way humans could grow wings.

Why can't we just grow a new set of limbs?

You can imagine this strategy working for some bugs like millipedes. Puedes imaginar que esta estrategia funciona para algunos insectos como los milpiés. Je kunt je voorstellen dat deze strategie werkt voor sommige bugs zoals duizendpoten.

Entire body segments could be duplicated thanks to mutations in genes controlling how the

body develops, and poof: you've got a new pair of legs to add to your 48 other pairs.

Mutations in a class of body-patterning genes called Hox genes have been linked to misshapen Las mutaciones en una clase de genes que modelan el cuerpo, denominados genes Hox, se han relacionado con la deformación corporal. Mutaties in een klasse van lichaamsvormende genen die Hox-genen worden genoemd, zijn in verband gebracht met misvormde

feet, hands, skulls, and even extra fingers or toes.

In very rare cases humans are even born with extra limbs, like this baby who was born with

three arms.

But almost always, these duplicated limbs don't function, because the new limb also Aber fast immer funktionieren diese duplizierten Gliedmaßen nicht, weil die neue Gliedmaße auch

needs bones, joints, its own muscles and nerves, and each of those duplications would require braucht Knochen, Gelenke, eigene Muskeln und Nerven, und jede dieser Verdoppelungen würde eine

countless other mutations in other genes.

That's beyond unlikely. Eso es más que improbable.

Evolving wheels instead of feet, or finding a fish with a propeller, or modifying our

hands into wings like a bat, is difficult enough to be impossible.

But at the end of the day there also has to be a need to evolve - you don't just get

something because it's cool.

This is perhaps the worst car ever made in the history of driving.

The Trabant had a 25 hp two-stroke engine closer to what's in a lawnmower than a car,

a plastic body, no fuel door, no rear seatbelts, not even a turn signal indicator. una carrocería de plástico, sin puerta de combustible, sin cinturones de seguridad traseros, ni siquiera un intermitente.

Although their design changed little from the late 1950s through 1990, when production

ceased, more than 3 million were sold.

That's because this was one of the only automobiles available in Communist East Germany.

Before the fall of the Berlin Wall in 1989, East Germany was a closed economy, meaning

there was no competition from other car manufacturers and no pressure to improve this vehicle.

For natural selection to happen an organism has to run into some challenge that impacts Para que se produzca la selección natural, un organismo tiene que enfrentarse a algún reto que repercuta en su salud.

its survival, what we call a selection pressure. su supervivencia, lo que llamamos una presión de selección.

The East German lawnmower sedan never had selection pressure from other automobiles La berlina cortacésped de Alemania Oriental nunca tuvo la presión selectiva de otros automóviles

forcing it to improve, so it continued to sell well despite being very bad.

Sauschlecht! ¡Sauschlecht!

Until humans experience a selection pressure for gliding, we won't start to evolve adaptations

that lead towards flight.

And sometimes selection pressures can be so sudden or different, that there is no adaptation

for evolution to even act on. para que la evolución actúe.

The dodo had no adaptations for defending itself, because it never encountered humans

or other predators, and well, we all know how that ended. u otros depredadores, y bueno, todos sabemos cómo terminó eso.

But beyond all these principles of evolutionary biology, one of the biggest limitations we

face is physics.

PHYYYYYYYSICCCCSSSSSS!!!

The reason we don't see gigantic land animals like Mr. Longneck here any more, is because La razón por la que ya no vemos animales terrestres gigantescos como el Sr. Longneck aquí, es porque

of two pesky bits of physics. de dos molestos trozos de física.

One, gravity.

You're probably familiar with that one.

Personally it's how I stay so down to Earth. Personalmente, así es como mantengo los pies en la tierra.

Heh.

Two, the square-cube law. Dos, la ley del cubo cuadrado.

As an organism gets bigger, its volume increases much faster than its surface area. A medida que un organismo crece, su volumen aumenta mucho más rápido que su superficie.

So as something grows and gets more and more volume, any process that depends on the amount

of surface that you have will become less and less efficient unless you change your

shape to make more surface.

This is the reason big complex organisms like us are multicellular instead of 6-foot-tall

single-celled amoeba blobs.

That wouldn't provide enough surface area to exchange nutrients and waste and make energy

for all of our big blobby volume.

So instead our bodies are made of 37 trillion cells, give or take.

It's the only way to have enough surface area for all… thissss.

Gravity and the square-cube law combined is why here on Earth it's unlikely we'd ever Zwaartekracht en de wet van de vierkante kubus gecombineerd is waarom het hier op aarde onwaarschijnlijk is dat we dat ooit zouden doen

get land animals weighing more than 100 tons.

It's also the reason if you're ever given the choice of fighting one horse-sized duck

or 100 duck-sized horses, you should pick the fight versus a horse-sized duck because

duck legs would snap like toothpicks under the weight.

And the limitations of physics are not just something animals have to worry about.

Calculations of how gravity affects the flow of water in trees estimate the maximum height

a tree could ever reach on Earth is 130 meters.

And sure enough, the tallest tree we know of… is just under 116 meters tall.

However, a different physical environment comes with different physical restrictions.

Blue whales, the largest animals to ever live on Earth, weigh up to 173 tons because the

buoyancy provided by their watery environment counteracts the gravity.

Therefore, on different planets with lower gravity or different atmospheric composition,

we might be able to see bigger animals.

For instance, 300 million years ago the concentration of oxygen in Earth's atmosphere was much

higher than it is today (reaching as high as 30%).

And insects which don't have lungs and circulatory systems like we do—they breathe by gases

just diffusing into their bodies—were able to grow much larger than insects today.

Dragonflies the size of birds?

Not thankyou sir.

For all of nature's creativity, a few empty spots remain on the tree of life where branches

seemingly can't grow.

What we call impossible phenotypes, that as far as we know have never arisen in the history

of Earth.

Like freshwater coral reefs, or birds that give birth to live young.

Or plant-eating snakes.

I mean, there are thousands of species of snakes!

You'd think one would take advantage of the food source that all other snakes are

ignoring and go vegetarian!

Snakes' closest relatives, lizards, many of them eat plants.

I mean, making the switch from a meat eating to plant diet worked for pandas.

Well, barely.

But maybe there's something about how a snake is built that prevents it from getting

enough energy from plants.

Of course maybe we just don't know.

For a long time it was believed that all spiders were carnivorous, until we found one that

eats plants.

It's difficult to say things are totally impossible.

Given more time, evolution may well produce some of the things we've talked about.

Imagine if alien evolutionary biologists studied life on Earth 450 million years ago.

Flowering plants, flying insects, animals able to walk and breathe on land… these

may have seemed like impossible phenotypes back then, but all of them happened.

So while there are limits to what evolution can do in single lineages, like humans growing

wings or animals with wheels, we don't really know where the boundaries of evolution are

as a whole.

Like… what about animals with an odd number of limbs?

I don't mean three limbs like Simone's super cute dog Scraps.

A three legged dog is a four legged animal that lost a limb due to an accident or medical

issue.

Or a 5-limbed animal like a starfish—radial symmetry removes many of the limitations that

would prevent odd numbers of limbs.

I mean a three-limbed animal like a dolphin.

Think about it.

How many “legs” does a dolphin or whale have?

Their fins have two lobes, and their prehistoric ancestors walked on all fours, but for all

intents and purposes couldn't we consider a dolphin an animal that evolved to move with

three limbs?

Does that mean kangaroos and their powerful tails, or monkeys with prehensile tails are, Betekent dat dat kangoeroes en hun krachtige staarten, of apen met grijpstaarten zijn,

functionally speaking, 5-limbed animals?

Are snakes one-limbed animals?

In these cases, although they are rare, there was an evolutionary path that allowed an odd

number of limbs or limb-like appendages to arise from even-numbered ancestors… that's

a pretty remarkable leap.

For all the rules and impossibilities we've talked about, the things evolution has been

able to mold and create are pretty impressive.

Instead of looking at what nature hasn't built, maybe we should marvel at all that

has been.

Stay curious.

We're still not gonna grow wings though.