The frog boil metaphor illustrates how it's easy to miss small changes that build up over time until it's too late. The scenario, as told, is that of a poor frog who would leap away from hot water but, if put into cooler water that is gradually warmed, won't respond in time to getting boiled.

As a metaphor, it describes a powerful and pernicious shortcoming in how we perceive the world. A student kitchen that gets messy mug-by-mug, a business with gradually slowing sales, a river that is slowly polluted, a road that gets busier each day, a bay that sees fewer fish each year, content that drifts, cancer that slowly spreads, a story or behaviour that becomes normal, a website that gets slower feature-by-feature, or a climate that slowly warms are all cases where we may not be happy where we end up, but we didn't notice how we got there.

It's hard to respond to gradual change, especially when it spans generations. Jared Diamond called it out as a potential fate of the Easter Islanders and how they could have cut down the last tree. One barnacle is nothing, but many barnacles can cause significant headaches for big ships.

Fortunately, there's a flip side. Many, many things are getting better without us realising. Small positive changes, such as in attitudes, education, or healthcare, add up over time—the Destiny Instinct can mislead us. Fast and slow layers make a system, like a forest, more robust. Getting one percent better each day leads to a 37x improvement in a year. And enough molehills can make a mountain.

What a frog does, in this case, is not, apparently, true—don't try it—it's much better as a metaphor, not an experiment.

The frog boil metaphor

I've always been fascinated by how a tiny spider can create a web spanning a gap where climbing and dragging a thread across the floor would be impossible, maybe between trees, from a building to a lamppost, or over a stream. How do they do that? Here's a common technique by many orb weaver spiders — known for building orb-shaped, or circular wheel-shaped webs — for bridging the gap and creating the web.

The spider stands on the edge and lets out a long thread. It waits for the breeze to blow the thread away from them. If the thread catches onto something it can form a bridge thread.

Once it catches, the spider may reinforce the thread and then put down other anchors. These then form the frame of the web into which it will add radial threads from the centre.

The spider may then put down an auxiliary thread that provides a non-sticky frame, together with the radial threads, for it to walk on while it lays down the final sticky capture spiral. It's then set to lie in wait.

Some spiders will eat their webs at the end of the night but leave a bridge thread in place — perhaps for you to walk into in the morning — ready to rebuild the next night.

There is a vast diversity of spiders and webs. This is a fairly common example, but even within orb spider webs, there are a ton of different strategies for capturing prey. But perhaps, the next time you spot a bridge thread spanning a seemingly impossible gap this will give you a thought as to how it might have been done.

Here's a common orb spider web as a static sketch

You can watch darwin's bark spider on the BBC creating a web spanning a remarkable 25 metres

A common orb spider web

A swan in Europe was a white swan. So, naturally, swans were thought of as only white by Europeans until news came from travelers to Australia in the late 1600s where black swans are in fact relatively common. Black swan events can turn a worldview upside down. They are unprecedented, unexpected, rare, and with a significant impact.

The infrequency of black swan events means prior data about them is too little to reliably guess the likelihood of one, and you may not even think to anticipate the event anyway. Except after the fact, when all of a sudden many people will claim to have predicted it — black swan events are prone to be rationalised in hindsight, believing that all the signs were there beforehand even if they weren't.

The idea of black swan events is from Nassim Nicholas Taleb. He writes:

"One single observation can invalidate a general statement derived from millennia of confirmatory sightings of millions of white swans. All you need is one single black bird."

Examples Taleb gives include the September 11 terrorist attack, the 2008 financial crisis, World War I, or the rise of the Internet.

More Taleb sketches: on mistakes, the firehouse effect, and the Lucretius problem. Also, hindsight bias.

Black swan events

The chaos monkey is a smart piece of software and a brilliant idea from engineers at Netflix.

The chaos monkey deliberately switches off servers in live environments at random. It takes the pain of disappearing servers and brings that pain forward. By deliberately sabotaging their own systems it created strong alignment for the team to design-in redundancy and automation for the necessary resiliency and reliability in the face of random failures. Training for this randomness helps make stronger, more resilient and fault-tolerant systems and software and keeps your movie streaming so you can keep chilling without interruptions.

The chaos monkey is a great metaphor and trigger to actively work on what life could throw at your system before it happens.

More monkey inspiration for writing and for bananas.

Chaos monkey

Content drift is how a piece of linked content may change over time such that what was once linked may in fact now be very different.

An article you link to may be corrected, opinions may be changed, content may be expanded or removed, a paywall may be put in the way, and yet the link keeps steadfastly pointing. Content drift, along with link rot — pages being lost — is one of the ways that the information we have come to rely on on the internet can be gradually undermined.

Here's a thread on content drift and link rot from Harvard's Jonathan Zittrain — at least, it was a thread on it when I wrote this. Also see: The Internet is Rotting.

Content drift

Yak shaving describes how when setting out to do something, you found you had to first do something else, which needed you to finish this other thing, and so on until you found yourself shaving a yak, or equally unrelated activity, to do the first thing you set out to do.

It's pretty common in life — tidying your room? — and particularly resonates in software development where when tackling one thing you find yourself fixing something else, which needs you to fix something else, and so on. Here's the ever brilliant xkcd on fixing problems.

The first I found of yak shaving was a short article on productivity in the first issue of Make magazine by Danny O'Brien and Merlin Mann.

Yak in the style of Alison Green and Adam Stower's excellent children's book, What can you Stack on the Back of a Yak?

Yak shaving

So you know some camels have one hump and some have two. Well, many moons ago a reader, John, shared with me a foolproof way to know which camel you’re looking at. The bactrian camel, found in Central Asia has 2 humps, just like a B on its side, while the dromedary camel, found generally in the Middle East, has one hump just like a D on its side. Never wonder again.

You may also like stalactites, stalagmites or other “What’s the difference between” sketchplanations: tortoise/turtle, crocodile/alligator, dolphin/porpoise, centipede/millipede.

Bactrian or dromedary camel? Never be confused again

The story goes something like this. Back in colonial India the top Brit in charge decided there were too many cobras around Delhi. To reduce the population they put in place a cash reward, or bounty, for anyone who brought in a dead cobra. The intention was clear. Legend has it that people did bring in the cobras reliably because some enterprising souls had started breeding cobras for the very purpose of getting the bounty. When the authorities realised this they scrapped the scheme, the cobra farms closed and the bred cobras were released into the wild significantly increasing the cobra population by a few orders of magnitude. Hence, the cobra effect: when a well-intentioned measure can have the opposite effect to that desired.

It’s not clear how true this story is, but the cobra effect has been demonstrated many times. The Freakonomics podcast on the cobra effect discusses some excellent examples (with references), including:

A bounty on rats in French colonial Hanoi — where the bounty was earned by bringing in a rat tail — which went the same way as the cobra story

Removing wild pigs at Fort Benning, Georgia, at $40 a pigs tail that didn’t make a dent. It could be the hunters would bait the pigs with all sorts of tempting scraps. Many pigs learned to avoid the hunters and instead bred like crazy while well-fed on scraps.

The capital of Colombia, Bogotá, tried to reduce traffic congestion by restricting each car from driving one day during the week. The result: people started buying more than 1 car and did more driving on weekends.

Publication of proposed areas of habitat to be protected for endangered species meant land developers responded by building in those areas before the land was protected.

People are smart. Incentives work, in the sense that you tend to get what you incentivise. So be careful what you are incentivising.

Also see: Goodhart’s Law and What gets measured gets better.

The cobra effect

For almost all mammals, 1.5 billion heartbeats, more or less, is how much you’ve got. From the teeniest, tiniest shrew weighing just a few grams to the largest whale — passing through animals as diverse as robins, monkeys, sea lions, and giraffes — each mammal has broadly in the region of 1.5 billion heartbeats.

Beyond just heart rate, knowing a mammal’s weight can help predict several other fundamental aspects of its life. A tiny mammal will likely have a heart that goes like crazy, live only briefly, and reach maturity quickly. A large animal, in contrast, will have a slow heart rate, a long life, and take its time to adulthood.

The most significant outlier is us, mainly because, in recent years, we’ve significantly extended our lifetime from what would be expected from Nature.

This gem, and many other fascinating insights about size, scale, Nature and physics, I learned once again from the book Scale by Geoffrey West.

1.5 billion heartbeats in a lifetime

Jared Diamond’s classic book Guns, Germs and Steel, proposes some remarkable hypotheses about how the pattern of history played out, notably trying to answer the question of why it was generally the Europeans that invaded much of the rest of the world rather than the other way around. One hypothesis, striking in its simplicity if you’ve ever looked at a world map, is the significant contribution of the general orientation of the major continents.

The Americas are largely lined up north–south, while Europe and Asia (Eurasia) are largely lined up east-west. An east-west alignment means the land generally has a more similar climate, day-length and seasonal variations. The general logic of the hypothesis is that the similar latitude of an east–west alignment means animals, crops, as well as travel and trade, more easily spread across the continents than across those with a north–south alignment — of the Americas and Africa — which naturally encounter more different climatic zones.

As a simplified example, horses and other large animals and crops spread throughout the shared temperate latitudes of Eurasia. In contrast, South America’s only large domesticated animal, the thick-coated llama (and related species like the alpaca), couldn’t easily spread to North America through the impassable tropical barrier of the isthmus of Panama. They just aren’t built for it.

There are a lot of viewpoints on the theory, and Diamond includes many more factors of geography and others — like never being able to domesticate the zebra — that go towards answering his question of why Spain invaded the Americas and not vice-versa. But ever since reading his simple hypothesis, available to anyone with a world map, I’ve found it hugely intriguing.

The continental axis hypothesis

Funny how it can take nearly 40 years to learn that something as commonplace as the stereotypical owl sound is made, not by one owl, but as a duet between the male and female tawny owls.

Also see: how owls’ necks turn so far around, or why do birds migrate so far.

The classic twit-twoo is actually a duet

For years, I’ve wondered at how as a kid I found the monkey bars in a playground (often a jungle gym in the US) so much easier to swing on than I do as an adult. And I see our kids swinging around easily on them, while now it’s hard for me just to hang off them. The reason why is partly to do with the square-cube law.

The square-cube law is the deceptively simple observation that as you scale up dimensions — say, as you get taller — then area of the object increases proportional to the square of the length, while volume increases proportional to the cube of length. This fundamental relationship has enormous significance in the sizes and shapes of animals and the limits of how big trees can get and how big we can build our bridges and buildings.

Because the strength of our bones, muscles or wooden beams is proportional to their cross-sectional area, this means that while the strength of a larger object, assuming the same proportions as the smaller one, increases according to the square of a length, the weight (from the volume it takes up) increases according to the cube of a length. So, relative strength decreases as size increases.

Some corollaries are therefore that children’s small size relative to the area of their muscles and bones makes them relatively stronger than adults and so they can more easily support their weight as they swing on the monkey bars. In the same way, press ups are harder for bigger people than they are for smaller. And while an ant has tiny spindly legs, those legs could easily support 50 other ants of its size, whereas for an elephant to support its own weight it needs chunky legs — not spindly ones — and there’s no chance it could get close to carrying 50 other elephants on its back.

It’s also part of the reason short trees can be spindly, but big sequoias have relatively chunkier trunks, and we need increasingly strong materials to build bigger and bigger skyscrapers compared to the shed in your garden.

Galileo discussed this back in 1638 and it still requires some getting your head around today.

For this and other fascinating insights of scaling check out Scale, by Geoffrey West.

The Square-Cube law

Owls are famous for being able to turn their heads seemingly full circle. It turns out some owls can turn their necks an amazing 270 degrees whereas our necks turn a measly 180 or so — see if you can turn your chin along your shoulder on both sides.

However, it’s likely the cause for this amazing feat is that, unlike our eyes, theirs are set facing forward and don’t rotate. So rotating their head becomes a key skill. Biomechanically they are able to turn so far by having twice the neck vertebrae as we do. If each vertebrae turns a little then having more helps them twist much further than us.

And yet the real trick is turning your neck while maintaining blood supply to your head through the arteries that also run up your neck. Rotate too far and the arteries can twist, stretch or be impeded. Owls have evolved a number of nifty strategies to help them turn their necks while maintaining blood flow. These include having the large carotid arteries towards the centre where they twist less than ours do, which run up the sides of our vertebrae. They also have loads of space around the arteries that run up inside the vertebrae and an area that may pool with blood at the base of the skull to provide a kind of reservoir if flow gets restricted. And more. All kind of amazing.

How owls’ necks turn so far round

A distinctive line below which you don’t tend to see leaves or branches in places with animals that like eating leaves or branches. Basically, caused by animals eating as high as they can reach — except for where there are giraffes where trees don’t stand much of a chance, even spiky ones.

The browse line

Not the easiest switch to make but given that jellyfish and starfish are not at all fish there is a move to call them sea jelly and sea star. As long as we all work to help protect them clearly it doesn’t matter a whole lot, but I think the move to sea jellies and sea stars makes good sense alongside others like the sea horse, sea cucumber, sea lion, sea lily, sea gooseberry…well, actually the sea horse is a type of fish, but you get the idea.

Sea jelly, sea star

For a closer look next time you’re at the beach. Pay close attention to whether you find one with a dextral or sinistral aperture.

Gastropods are the largest class of molluscs which includes limpets, snails and sea slugs. For those who weren’t sure.

Info from Discovering Sea Shells by Barry Charles

Typical gastropod anatomy

There’s a famous photo series by Eadweard Muybridge that shows, unequivocally, that while galloping all four of a horse’s legs leave the ground. I’d always heard that’s what they trying to find out at the time, but from what I’ve read it was more a question of at what points do a horse’s legs leave the ground. The photos show the somewhat surprising state of leaving the ground while the horse’s legs are tucked, not when they are outstretched. It’s a lovely example of what Edward Tufte calls small multiples.

Do horses legs leave the ground at a gallop?

Venomous animals inject venom through bites, stings and the like. Think snakes, spiders, stingrays…

Poisonous animals poison you if you absorb - perhaps by touching the skin of a poisonous frog - consume - perhaps by eating a poisonous animal - or inhale the poison - perhaps by breathing in some poisonous spores. Think amphibians, plants, fungi…

Venomous, poisonous - what’s the difference

All of these guys can grow back major parts of their body, even limbs, and in the case of the flatworm a new head. Crazy.

Animals that regenerate

Bycatch is other stuff you caught when trying to catch something else. Bycatch makes me sad. Any fish or sea creatures can be caught unintentionally during fishing, and it also affects larger animals such as sharks, turtles and of course dolphins. When learning from a whale shark expert on the island of Utila in Honduras he told us one of the simplest ways to help is to give up eating prawns. As London’s Maritime Museum puts it:

“For every kilo of tropical prawns you buy, 15 kilos of unwanted sea-life may be thrown back dead as ‘by-catch’. Trawling for prawns can also trap turtles, unless a special device keeps them out of the nets. Farming prawns is often no better, since mangrove swamps may be destroyed to make room for prawn ponds.”

Prawns are particularly bad as they are often caught with bottom trawling. I once read a description of it as wanting to catch a cow, and choosing to drag a net by helicopter over the entire farm, and so also catch the tree in the garden, the dog, the pigs and the farmer’s wife in the process.

Check out the WWF bycatch page for more including a bottom trawler in action.

Bycatch

The length of your arms relative to your height. Typically:

Da Vinci’s classic Vitruvian man has an arm span equal to his height and therefore an ape index of 1. An ape index greater than 1 (arm span longer than height) seems to be helpful for rock climbers, swimmers (Michael Phelps = 1.06), boxers, professional basketball and goalkeeping.

It’s also known as the gorilla index though I couldn’t actually find a measure for gorillas remarkably. A quick calculation shows for an average male gorilla at 1.75m tall and arm span of 2.45m that the gorilla index for a real gorilla would be = 2.45 / 1.75 = 1.4. I’d definitely fancy the gorilla in rock-climbing and boxing…

It’s sometimes calculated as arm span minus height, that would give gorillas a ridiculous: +70

I have not been able to figure out if your ape index changes from a child to adult though it seems like it might.

Ape index

Well, the barnacles we see don’t move. But when they’re little, they do swim, and once they’ve found their spot they basically cement themselves in place. They’re what’s known as sessile animals — ones that don’t move once settled, along with mussels and coral. Now that would be a different way of life.

How do barnacles move anyway?

And, let’s face it, most of us are more likely to encounter camels in the Middle East and Africa than trekking around the Gobi Desert. The wild bactrian camel is sadly on the critically endangered list.

And, there is this simpler way to remember the difference that a reader passed on to me: dromedary is one hump like a D on its side, and bactrian is two humps like a B on its side. Simples.

Camel identification: 1 hump dromedary, 2 humps bactrian

A centipede has 1 pair of legs on each body ring, and a millipede has two on most body segments. Hence millipedes will generally have plenty more legs to go round. As far as I know this is fairly foolproof. Though generally speaking there are more obvious ways to tell, such as millipedes looking more like long armoured nice round worms and usually moving slowly, and centipedes zipping around while generally seeming more long-legged and insecty, with longer antennae at the front and longer angled back legs, sometimes with hooks for defence.

If you were offered to pick one of them up, you’d probably pick the millipede.

Also, in case you were tempted to think they are insects, they’re not because insects have six legs. They are arthropods (loosely meaning jointed feet) along with insects, spiders, scorpions and crustaceans, but in their own subphylum of, aptly named, myriapoda (loosely meaning many legs).

Check out core insect anatomy for a sketchplanation insect refresher.

How to tell a centipede from a millipede

Nifty water camouflage practised by dolphins, porpoises, some fish and other neat sea creatures. The simple strategy: look light like the sky for anyone below, and look dark like the sea for anyone above. 

Counter-shading

…regulate temperature and (maybe) to keep feathers clean while eating. Keeping the feathers clean was my inspiration for this sketchplanation - there’s something about the cold practicality of not messing up your feathers while you’re tucking into some carrion. However, it looks like it is more likely to be for the more prosaic reason of regulating temperature and keeping cool. As Dominic McCafferty, at the University of Glasgow points out:

‘…other groups of scavengers, particularly giant petrels, have feathered heads. Large mammalian scavengers also don’t have bald heads, so why vultures?’

Should you be interested, read more at the University of Glasgow’s Why do vultures have bald heads?

Vultures have bald heads to…

What's the difference between a dolphin and a porpoise? It's not always straightforward.

It’s not fullproof (there are a few exceptions) but pretty much these’ll do it for you.

What’s the difference between a dolphin and a porpoise

I could never remember which was which and here is the way to remember it: when bulls attack they swipe up, and when bears attack they swipe down — just like their respective markets.

Bull market, bear market

Pay attention to the jaw, teeth, habitat and location and you’ll be 99%.

What’s the difference between a crocodile and an alligator

Know your poles

If you remember nothing else, remember that tortoises are on land, and turtles are found swimming.

What’s the difference between a tortoise and a turtle

Head, thorax - with 6 legs or wings, abdomen and an exoskeleton and you have an insect. One of over a million species. As impressive as snowflakes.

Sketchplanations tagged with animals