Perhaps you’ve seen online a photo of two friendly little penguins that meet in the evenings to admire the Melbourne city lights reflected in the sea, flipper in flipper? I have to admit that I was initially sceptical about the shot. But was I right to be? Are only humans capable of delight?
You don’t have to be a romantic to notice that the natural world is full of beauty. From picturesque landscapes to unbelievably colourful birds and fish – all around us there are sights that can provide a moment of aesthetic pleasure even to those who are unlikely to be overcome by emotion. I myself am not overly effusive – or at least I don’t consider myself to be – but I find it hugely aesthetically satisfying when, for example, my ship weighs anchor in Ilulissat in Greenland and enters the fairy-tale world of a golden-crimson sunset and incredibly blue icebergs reflected in the expanse of liquid gold. In moments like these, I can almost hear a quiet clicking in my head: everything suddenly falls into place and I feel that the world surrounding me is exactly as it should be. There’s no place I’d rather be.
It is with a less satiating but fiercer delight that I admire details, such as the colours of the mandarinfish or the Picasso triggerfish. By the way, it would have been easier for me to write about this if “Przekrój” had been an eyesore of a magazine, garish with photos – only then I wouldn’t want to write for it. So please, when you have a moment, do yourself a favour and look up photos of the animals I mention here, because they’re extraordinary. Of course, flowers, butterflies and fly agarics are also pretty, and I – although I’m possibly not completely objective – would also mention king penguins among the creatures with the most beautiful colouring. There probably isn’t a tough customer in the world who wouldn’t utter at least a quiet moan of tenderness at the sight of the leaf sheep (Costasiella kuroshimae) or, really, any of its nudibranch relatives.
In the eye of the beholder
We can see all this delightful diversity thanks to the cells in our retina, which transforms light into nerve impulses, and the ability of our brain to interpret these signals. As a reminder: the human eye features two main kinds of photosensitive cells. Rod cells are responsible mainly for the perception of shapes and movement, and they allow us to see in semi-darkness. Cones deal with colours. Most of us have three sets of these: each of these reacts most enthusiastically to various wavelengths of lights. Some of our cones are stimulated most strongly by waves that are 420 nm long (we see them as blue light), others react best to 534 nm (green), and others still – to 564 nm (red). All of them send messages to the brain, where they are interpreted and analysed, and where a colour image is created. For example – as you probably remember – the light that we perceive as white is just a mixture of electromagnetic waves of varying lengths. So beauty really is born in the eye of the beholder, and although most of us can agree on the fact that something is blue, it’s possible that each of us perceives that blueness differently.
Different animals have different tools at their disposal. We have three types of cones, but butterflies have five. The peacock mantis shrimp – the world’s most unbelievable crustacean, Darwin must have been under the influence of some extremely interesting chemicals when coming up with it – has no less than 16 types! What’s more, each of its two eyes can see in 3D, because both contain three centres of extreme perception precision. This means its one eye renders a more three-dimensional image than two of ours. Additionally, each one moves independently, on its own stalk, allowing for 360-degree vision. The mantis shrimp’s range of vision encompasses not only what we arrogantly call ‘visible light’ (or what humans can see), but also ultraviolet and infrared. As if that wasn’t enough, this crustacean can also see the polarization of light. We will never be able to imagine what the mantis shrimp’s world looks like.
But we don’t have to look for examples as exotic as that. Bees and many birds can also see the UV spectrum. Kestrels use this ability to find rodents. The urine of small mammals shines in ultraviolet, so the falcons hunting them search for purple traces. If the area is densely strewn with them, that means… urine luck. In ultraviolet light, even familiar objects look completely different. Starlings seem shiny grey to us, but in UV light they become colourful.
What’s the purpose of all this decoration? Sometimes, in itself, it has none: blood-red crabs live in the sea depths and their wonderful colouring is never seen by anyone, because no light penetrates there. It just turned out like this and evidently it is associated with no cost to them, so evolution had no reason to eliminate this irrelevant feature. The above-mentioned leaf sheep, in turn, owe their green colour to the symbiotic algae that they grow in their skin. This makes these nudibranchs the only animals in the world that are capable of photosynthesis.
However, very often colouring has a specific purpose and carries information. For example – although to us this is invisible – a bee looking at a flower will see on it clear ultraviolet lines leading to the source of the nectar, like arrows indicating the way at a museum. Sometimes the message is the opposite. In many animals – such as poison dart frogs and lionfish, but also in fire salamanders, fire-bellied toads, and wasps – gaudy colours warn enemies that the animals decorated with them are poisonous or venomous. (As an aside: if someone is venomous, you can die if they peck you; if they’re poisonous, you can die if you peck them. Either way, it pays to be careful – irrespective of the pecking order). Sometimes this messaging is a clever con. A species of kingsnake, the milk snake, has a red body marked with black and yellow rings. Although it is not venomous, its colouring is very reminiscent of that of another, venomous snake – the coral snake – which deters aggressors.
Frequently, however, colourful patterns serve not in war, but in love: they help to attract potential mates. Here’s the evolutionary rub. In 1860, a frustrated Charles Darwin wrote to his friend, the American botanist and evolutionist Asa Gray: “The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!” This reaction might seem a little strange – after all, peacock feathers are one of the most beautiful things in the world. And the whole peacock tail in general, the way the male shows it off to his female friends; how wonderfully long, rich and heavy it is… Exactly, here’s the problem. It’s almost impossible to fly with a tail like this. This is why the discoverer of natural selection had a serious problem. How, after all, could natural selection allow for something as impractical as the peacock’s tail – the symbol of all sorts of extravagant behaviours and ornaments that in no way facilitate survival and which nature is full of?
As was his wont, Darwin arrived at a solution to this problem arduously and slowly. In 1871, he published another ground-breaking work, The Descent of Man, and Selection in Relation to Sex. This was where he introduced the idea of sexual selection, which sometimes works in opposition towards natural selection. Very many species feature a clear distinction in the appearance of males and females, called sexual dimorphism. Males are usually either much larger or more colourful; they might have extra attributes (like the antlers of stags), they might sing beautifully (or at least loudly). Males compete for the females’ favour. There are a few species – such as jacanas, tropical birds that can walk on floating leaves, or phalaropes, shorebirds that live in the Arctic and Western North America – in which the female is larger and more colourful, but the principle is the same: here it is the ladies who compete for the affection of unassuming gentlemen. Then they lay eggs for them, leave them to care for the chicks, and depart to continue their conquests. I don’t like the saying about the exception proving the rule, but it fits jacanas and phalaropes to a T. According to Darwin, the selecting side has its own aesthetic preferences, so the selected ones develop precisely the characteristics that appeal to it, via evolution. That doesn’t sound too controversial or complicated, does it?
Unfortunately, Darwin didn’t know the principles of genetic heredity and he couldn’t explain how this could work in practice. His concept was immediately criticized by naturalists – more Darwinian than he was himself. One of them was Alfred Russel Wallace, co-creator of the theory of evolution, who claimed it was impossible for animals to have sufficient cognitive ability to evaluate the aesthetics of anything.
With time, however, various hypotheses emerged, according to which gaudy colouration might be proof of the suitor’s excellent health, lack of parasites, etc. This line of thinking culminated in the handicap principle (which I find very interesting), proposed in 1975 by Israeli ornithologist Amotz Zahavi. According to him, peacock tails and other such fripperies evolved precisely because of their impracticality. Males use them to send a signal that they’re so amazing that despite the obvious handicap they’re still doing well, so it’s a good idea to breed with them because they offer really fantastic genes. This ingenious concept can explain more than just costly decoration in birds. Robin Baker (a researcher studying the sexual behaviour of mammals, mainly humans, whose lectures I had the pleasure of attending in the last decade of the previous millennium) argued that the same mechanism applies to guys who buy expensive and impractical cars and who drink a lot – and now he’d probably add to the list those who go into space in their own rocket for a large amount of money that could be spent much more effectively and sensibly on our not-untroubled planet. Because I like to reach logical conclusions and appreciate the practical applications of scientific theory, I must remember that if I’m ever going to try to pick someone up, I need to cut off my right hand, having beforehand (it’d be hard to do it one-handed) attached a ball on a chain to my leg. I’m sure nobody could resist me…
Tails and bowers
So perhaps this is a dead end? Maybe it would be worthwhile, after all, to return to Darwin’s original idea and admit that females can choose their partners on the basis of aesthetic preference? It was as early as in 1915 that the British biologist and mathematician Ronald A. Fisher grounded this idea in mathematical algorithms, presenting the genetic mechanism of sexual selection. According to him, elaborate ornamentation comes about in two stages. Initially – as Wallace posited – an attractive appearance would, in fact, signal the candidate’s good health: choosing beautiful partners would then lead to having high-quality offspring. But this offspring would inherit not only the good health, but also the characteristic that signalled it, and a certain preference for that characteristic. If it is, for example, a longer tail in the male, the offspring of such a couple would inherit both the long tail genes (sons from fathers), and the genes of being attracted to longer tails (daughters from mothers). In subsequent generations, the males’ tails can then grow longer, and females might be more likely to choose them.
In this way, sexual selection can detach from the logic of natural selection and have grotesque, impractical results. Fisher called this ‘runaway selection’. This mechanism can explain the emergence of ornaments as absurd as the antlers of the giant deer, also called the Irish elk. It was about the size of the modern elk, but its antlers were 3.5-metres wide! However, although the mills of natural selection grind slowly, they do grind exceedingly fine, and these bizarre animals went extinct a little over 7000 years ago. Their resplendent ornament, weighing up to 40 kilograms, turned out to be too costly in the long term.
But does this prove that animals – apart from the Homo genus – are capable of delight? We don’t have much of a problem with accepting the fact that our ancestors could experience it. Currently, we consider the oldest known work of art to be some bones of the above-mentioned giant deer decorated with a chevron pattern by our cousins, the Neanderthals, 51,000 years ago. Homo sapiens, in turn, made beautiful rock paintings throughout the world several dozen thousand years ago. By the way, the most famous European cave to be decorated with paintings, the one in Lascaux, was discovered in 1940 thanks to a landslide. Earlier, it would have been accessed by a narrow tunnel about a kilometre long, which the neolithic artists squeezed through. What sort of person laboriously crawls into the bowels of the Earth, in absolute darkness, to create works of art that will never see the light of day? The longer I think about it, the more delighted I am.
In 2012, in Cambridge, the world’s most eminent neuroscientists signed the Cambridge Declaration on Consciousness. Thus, the so-called Western science finally admitted that other animals also have personalities, feelings, emotions and character. I consider this event to be incredibly embarrassing: had these experts never lived with a dog or a cat? I have been a companion to seven cats so far in my life and each one of them was completely different. But, apparently, better late than never, so we mustn’t grumble. Anyway, now we officially know that we don’t have a monopoly on being able to perceive the world through a lens other than edibility. So there is nothing to stop us from admitting that others can also like something because they consider it pretty. From this perspective, it’s much easier to understand the dazzling breeding plumage of birds of paradise, or their incredible dances and displays. The above-mentioned peacock tail really could have evolved thanks to the peahens’ unique sense of aesthetics. And it really is very sophisticated – various experiments have shown that peahens are most partial to tails that have 144 or more eyespots. Below that magical number, males can’t expect spectacular success, but above it ladies don’t really mind and more numerous eyespots don’t make a difference.
There are, however, birds that make the glorious peacock look amateurish. One of them is its relative – the great argus. Darwin was in awe of it, and Richard O. Prum writes in his book The Evolution of Beauty that the bird bears the most complex ornament in the animal world. Apart from other subtler patterns, the whole length of its abundant flight feathers is decorated with many eyespots (hence the animal’s name, referring to the 100-eyed giant Argus from Greek mythology); their shading makes them look like three-dimensional baubles. The further they are from the base of the feather, the larger they are, so when the argus suddenly surrounds the female with the dome of his spread wings, she finds herself in a marvellous world full of equal-sized shimmering baubles.
Male displays aren’t limited to exquisite dress. Some suitors create sophisticated structures in order to seduce fussy partners with real estate. The satin bowerbird removes all twigs and pebbles from his plot, and then decorates it with colourful – most often, blue – objects. In the middle, he builds a bower: its purpose is solely for copulation, as long as the beloved can be tempted. But the most incredible seduction constructions are built not by birds, but by some pufferfish – inconspicuous fish known for filling their bodies with water in moments of danger, and turning into inedible, spiky balls. Their males laboriously etch the sand on the seafloor into wonderful decorative circles up to two metres in diameter; it takes them a few days of hard work. We find this delightful, but why do we find it so hard to understand that a female pufferfish can honestly enjoy the sight of such a circle?
It was a long time ago now that Darwin wrote that the differences between us and other animals are only quantitative, not qualitative. This means that there are no characteristics which are distinctive to humans – we have just developed some of them to a higher degree. Which is why – despite my initial scepticism – I like to think that the penguins in the Tobias Baumgaertner photo mentioned at the very beginning just like the sight of the night-time city lights reflected in the bay. And a dog who loves us really considers us to be the most beautiful creature in the world, even early in the morning.
Translated from the Polish by Marta Dziurosz
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