Color my world

When you think about it, color vision is kind of strange.  Our eyes -- unless you have a genetic or physical inability to do so -- are able to sort out the frequencies of light, and each range in the visible light spectrum looks different to us.  But why do we have the ability to distinguish between, for example, light with a wavelength of 570 nanometers (which looks yellow) and that with a wavelength of 470 nanometers (which looks blue)?  It's a small shift in wavelength, but triggers a completely different response in our eyes and brain -- so it must be important, right?

Color perception in the natural world seems to serve a fairly small number of functions.  There's sexual signaling -- the (often) brighter colors of male birds, for example, is most likely a cue for females signaling fitness (and thus good genes, worthy of producing young with).  It can be a sign that food is ready to eat, such as fruits changing from the blend-with-the-foliage shades of green to something more eye-catching.  It can also be a danger signal, as with the brilliant warning colorations of coral snakes, the foul-tasting bright orange and black monarch butterfly, and Central and South America's dart poison frogs.

So our ability to sense colors, an ability shared with many other mammals, birds, reptiles, amphibians, fish, and some arthropods, seems to have evolved as a way of distinguishing things that need to stand out from the background, for purposes of reproduction or survival.  There's a reason, for example, that stop signs are red; our dim-light vision is poorest in the red region of the spectrum, so when car headlights catch a bright red stop sign at night, it immediately grabs our attention.  (The flipside of this phenomenon is why snow under moonlight looks blue.  It's not that snow preferentially reflects blue light; it's simply that our eyes are better at picking up the blue region of the spectrum in low light levels, so it's almost as if our eyes are subtracting the red frequencies from the white light reflected from snowbanks, resulting in it appearing blue.)

What this means, of course, is that pigment production has to have evolved in tandem with color perception.  There are undoubtedly exceptions, where colorful chemicals have evolved for other purposes, and their hues are accidental byproducts of their molecular structure; but otherwise, the evolution of bright pigments must have coevolved with the ability to perceive them.  The brilliantly-colored organic compounds produced in the petals of many flowers, for example, are generally for the purpose of attracting pollinators, and the reds, oranges, and yellows of ripe fruit attract animals to consume the fruits and then disperse the seeds.

Scarlet passion flower (Passiflora coccinea) [Image licensed under the Creative Commons gailhampshire from Cradley, Malvern, U.K, Scarlet Passion Flower - Flickr - gailhampshire, CC BY 2.0]

What's curious about this, and why the topic comes up today, are the findings of a study out of the University of Arizona that appeared in the journal Biological Review last week.  It showed that based on genetic studies of distantly-related animal groups, color vision evolved a very long time ago -- on the order of five hundred million years ago, so the middle of the Cambrian Period -- while the first fruits didn't show up for another 150 million years, and the first flowers 150 million years after that.

So the earliest production of functional color (and the ability to perceive it) almost certainly was driven by sexual signaling and warnings.  Then, once animals were able to see in color, it became an evolutionary driver in plants to ride the coattails of that capacity in order to facilitate cross-pollination and seed dispersal.

And once that back-and-forth coevolutionary relationship was in place, it was off to the races.  Give it another couple hundred million years, and we have the rainbow hues of the natural world today.

One thing I still find hard to explain -- from an evolutionary standpoint, at least -- is why we find brightly-colored things beautiful.  Having our attention caught by a bright red apple, or the wild stripes and spots of the venomous lionfish -- sure, those make sense.  But why is it almost universal to find a daffodil or a wild rose beautiful?

Ah, well, maybe it's just one of those accidental things that is a consequence of other, more vital, evolutionarily-derived traits.  Whatever it is, we can certainly still enjoy it, and not let our wondering why it occurs interfere with our appreciation.

But it's still kind of cool that the ability that allows us to have that experience goes back at least five hundred million years.

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The disappearing elephant

Ever heard of gomphotheres?

They're a group of prehistoric megafauna related to modern elephants with some pretty wacky-looking dental adornments.  There was Cuvieronius:

[Image licensed under the Creative Commons DiBgd, Cuvieronius hyodon2, CC BY-SA 4.0]

And Stegatetrabelodon:

[Image licensed under the Creative Commons ДиБгд, Stegotetrabelodon11, CC BY-SA 4.0]

And strangest of all, Platybelodon:

[Image licensed under the Creative Commons Tim Bertelink, Platybelodon, CC BY-SA 4.0]

Illustrating that it's a good thing I'm not in charge of assigning scientific names, because I'd'a named this one Derpodon bucktoothii. 

In any case, these behemoths were once widespread across North America and Europe, but gradually died out during the Pliocene Epoch (5.3 to 2.6 million years ago), with the last species persisting a little way into the next epoch, the Pleistocene.  Probably for the best, actually.  I have a hard time keeping rabbits and woodchucks out of my vegetable garden, I'd just give up if I had to fend off these things as well.

Where it gets even more interesting is that these animals, like (literally) millions of others, had coevolved with other life forms.  Coevolution -- when the adaptations of one species effect the adaptations of an unrelated species -- can take two forms.  First, there's an evolutionary arms race, where a predator/prey relationship pushes both species to evolve (such as cheetahs and antelopes, where the fastest cheetahs catch the slowest antelopes, selecting both for greater speed).  The other is mutualism, where each of the two helps the other, like flowers that have adapted to specific pollinators, sometimes resulting in such dependence that neither species can survive without the other.

It's this latter type that happened with the gomphotheres.  They were major seed dispersers -- eating fruits of trees and shrubs, then defecating out the seeds (unscathed) after digesting the pulp.  Many of these plants still exist in North America and Europe, and all are united by having large, tough-skinned fruits, usually with hard or unpalatable seeds, and some sort of thorns or spikes on the branches to deter smaller animals from eating them.

There's only one problem -- as I mentioned earlier, all the gomphotheres have been extinct for millions of years.

So that leaves a bunch of plants without an efficient way of dispersing their seeds.  And we're not talking about exotic and unfamiliar plants, here.  If you look up evolutionary anachronisms, you'll see lots of names you recognize, including:

• Avocado (Persea americana)
• Papaya (Carica papaya)
• Cacao (Theobroma cacao)
• Custard apple (Annona spp.)
• Wild squash (Cucurbita pepo)
• Pawpaw (Asimina triloba)
• Osage orange (Maclura pomifera)
• Kentucky coffee tree (Gymnocladus dioicus)
• Honey locust (Gleditsia triacanthos)
• Devil's walking stick (Aralia spinosa)
• American persimmon (Diospyros virginiana)

Some of these, like cacao, Osage orange, and Kentucky coffee tree, have only prospered and/or expanded their range because humans intervened.  The last-mentioned, for example, was found only in a highly fragmented, restricted range in the south central United States when it was first cultivated by botanists and found to be a decent ornamental tree.  In the wild, the big, leathery pods -- like the fruit of a lot of these species -- simply fall to the ground when ripe and rot, the seeds nearly all failing to germinate.  Now it's planted throughout the eastern half of the United States, although given its poor germination rate even with help, the species will probably never be common.

Unless the elephants come back somehow.

This all illustrates a point I've made before -- the biosphere is a complex interwoven tapestry.  While change is inevitable -- and the extinction of the gomphotheres isn't the fault of humanity but (likely) the changing climate -- it behooves us to keep in mind that nothing on the Earth exists in isolation.  You can't pull out one thread without making the entire thing start to come unraveled.  And too many threads pulled out, the entire tapestry falls apart.

I can only hope we learn from what we've found out about the ebbs and flows of prehistory.  While we can't halt change, we need to do a far better job of protecting what we have.

Lest we go the way of the gomphotheres.

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The floral death trap

One of the most interesting features of evolution is coevolution -- where two unrelated species influence each other's evolutionary pathway.

It's usually framed as benevolent, providing a benefit for both species, as in the whistling thorn (Vachellia drepandolobium) of East Africa, which makes hollow spheres at the base of the spines.  These provide a home for various species of symbiotic ants, which help out the tree by attacking and killing insect pests that might eat the leaves.  (It's called "whistling thorn" because the wind blowing across the holes in the spheres makes a whistling noise.)

There's also the less pleasant sort, the best-known of which is the evolutionary arms race -- such as the cheetah and the impala.  The fastest cheetahs catch and eat the slowest impalas, thus pushing both species to (on average) get faster.  (The general consensus, though, is that the cheetah might have topped out in terms of potential speed -- the combination of their powerful muscles and flexible spine and limbs would make them prone to dislocations and stress fractures if they were driven much harder.)

A relationship that's usually portrayed as entirely positive, though, is the one between flowering plants and their pollinators.  One of the earliest vindications of Darwin's theory of natural selection came with his conjecture that the Star of Bethlehem orchid (Angraecum sesquipedale) of Madagascar, which has a ridiculously long hollow spur at the back of the flower (with the nectar glands all the way at the tip), must have a pollinator with mouthparts that fit it:

[Image licensed under the Creative Commons sunoochi from Sapporo, Hokkaido, Japan, Angraecum sesquipedale Thouars, Hist. Orchid. 66 (1822) (45523703575), CC BY 2.0]

Not long afterward, researchers discovered the Madagascar hawk moth (Xanthopan morganii praedictum), exactly as Darwin said they would:

[Image licensed under the Creative Commons Nesnad, Xanthopan morganii praedicta Sep 16 2021 03-58PM, CC BY 4.0]

In fact, the coevolution between flowering plants and insects is so varied and complex that some evolutionary biologists claim it's responsible for the explosion in biodiversity in both groups that started during the early Cretaceous Period.  This, they say, is why flowering plants outnumber all other plant species by a considerable margin, and insect species outnumber all the rest of Earth's species put together.  (My own opinion is that it's probably not that simple -- evolutionary drivers seldom are.  But I won't deny that coevolution played a significant role.)

What's kind of interesting, in a grim sort of way, is when the coevolution between plants and their pollinators takes a darker turn.  One example, that is so crazily complicated that I had students tell me I was making the whole thing up, is the bucket orchid (Coryanthes spp.) of South America.  These bizarre-looking flowers have some upright petals, but the lower ones are fused into a "bucket" that fills with sweet-scented nectar.  The pistil (the female part of the flower) is submerged at the bottom.  One genus of bees (Euglossa spp.) is attracted to the scent, but upon landing on the edge of the bucket, finds no place to hang onto and falls in.  It swims around trying to find a way out, but the sides of the bucket are coated with a slick wax that provides no traction.  There's only one place it can get out -- at the back of the bucket is a ladder (I shit you not) made of hairs the bee can hang onto.  But when it gets to the top of the ladder, it finds itself head-first in a long tube with no place to turn around, so it wriggles its way to the end -- in the process gluing the anthers (the male pollen-bearing structures) to its back.  At the end of the tube is a hole (whew), and the bee flies away.  But then -- not having learned its lesson, apparently -- it finds another flower, falls in again, and this time the nectar acts as a solvent.  The anthers it was carrying come loose and settle to the bottom of the bucket (remember, that's where the pistil is), and pollinates the plant.

[Image licensed under the Creative Commons Orchi, Coryanthes hunteriana Orchi 01, CC BY-SA 3.0]

But at least here, it has a happy ending -- the bee escapes eventually.  There are, however, plants that kill their own pollinators -- in fact, that's the reason this whole topic comes up, because another one was just discovered recently.

The first one I ever heard about that pulls this nasty trick is a species of African water lily (Nymphaea capensis).  It's deceptively beautiful:

[Image licensed under the Creative Commons Fan Wen, Nymphaea capensis (14) 1200, CC BY-SA 4.0]

The flowers open twice, on two successive days.  The first day, the pistils are inaccessible beneath a tight cone of stamens (the above photograph was taken on the first day).  Bees landing on the flower are doomed to disappointment, because the nectar is inside the cone, but in trying to get to it they coat themselves with pollen.  The flowers close at night, then when they open on the second day, the cone of stamens opens as well, exposing a tempting pool of nectar with (once again) the pistil at the bottom.  A bee, having just visited a first-day flower and come away with no food but lots of pollen, lands on the edge of the pool in the middle of a second-day flower, and falls in.  This time, though, there's no escape.  It drowns, and the pollen it's carrying settles to the bottom of the pool and fertilizes the flower -- thus ensuring the plant will cross-pollinate, not self-pollinate.

What brought this topic to mind was a paper I stumbled across yesterday in the journal Plants, People, Planet that describes the same sort of fatal deception, but using a different kind of lure.  A Japanese species of the genus Arisaema, which in the United States is best known for the spring wildflower we call Jack-in the-pulpit (Arisaema triphyllum), that is common here in the northeast.  They have bizarre flowers -- a long, inverted cone with a flap on top (it's actually a spathe, a modified leaf), and in the middle a narrow cylinder (containing the actual flowers themselves, which are tiny).  If they're not weird enough from appearance alone, wait till you hear what some of the Japanese species do.

Arisaema angustatum (left) and Arisaema peninsulae (right), two of the tricksters described in the paper [Photograph by Kenji Suetsugu] 

These flowers are pollinated by fungus gnats -- familiar as annoyances to anyone who owns a greenhouse -- pinhead-sized flies that are attracted to moist soil.  Well, the plants don't just lure them by pretending to be a source of food.  The researcher, Kenji Suetsugu of Kobe University, realized something else was going on when he found that inside the cone-shaped spathe there were dozens of dead fungus gnats...

... all of them male.

Suetsugu started analyzing what chemicals the flowers were producing, and found that like the water lily, the Arisaema flowers change during the time they're open.  At first, only the male flowers are open, and fungus gnats that find their way in (presumably lured by the musty smell the plant has) climb about and pick up pollen.  But then the male flowers close and the female ones open -- and the strategy changes.

When the male flowers only are open, there's a little escape hatch at the base of the flower, so the gnats can get out after picking up pollen.  But when the female flowers open, the escape hatch closes.  And that's when the plants start producing a new chemical: an analog to the sexual attractant pheromone female fungus gnats produce to attract the males.

So the poor male gnats, hoping to get laid, find their way into the flower, but there's no way out because (again like the water lily) the interior of the cone is slippery.  They climb around on the female flowers, pollinating them, but eventually die from a combination of exhaustion and frustrated horniness.

If you thought that the relationship between flowers and pollinators was all mutual happiness, think again.  "Nature is red in tooth and claw," as Alfred, Lord Tennyson put it.  He was thinking of predators and prey, but it isn't restricted to the animal kingdom.  There are plants that reward their pollinators with an unpleasant demise -- showing that once again, evolution finds a way to exploit just about every possible innovation you can think of, nice or not.

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The moth and the flower

Ever heard of an evolutionary arms race?

It's a twist on coevolution, where the adaptations in one species affect the selection -- and therefore the evolution -- of another, unrelated species.  In arms races, as the name implies, it's specifically about biological weaponry, either for predation or for self-defense.  Finding lunch, or avoiding being lunch.  The most commonly-cited example of an arms race is speed and maneuverability in the cheetah and the impala.  The fastest cheetahs take down and eat the slowest impalas; the fastest impalas escape, and the slowest cheetahs starve.  (That's an oversimplification, but it'll do for now.)  The upshot is that over time, both the cheetah and the impala evolve the ability to run faster.  The most common outcome of arms races is that it continues until one of the species kind of maxes out on how far it can take the adaptation.  The cheetah might well be at that point; it's hard to imagine how they could be any faster without the strain on the joints, tendons, and muscles causing serious injury.

The odd thing about an arms race, though, is that sometimes it can backfire on one of the participants.  A relationship like this was the subject of a paper last week in the journal Alpine Entomology, which looked at a beautiful -- but highly poisonous -- plant, the alpine rose.

The alpine rose isn't a rose at all; it's a species of rhododendron (Rhododendron ferrugineum) that lives in a habitat not much else can tolerate.  It thrives only in rocky, acidic soils, just above the tree line in the Alps, Jura, Pyrenees, and Apennines.  Besides the obvious difficulties of living in a cold, windswept place, there's the issue that in such barren areas, any animals are going to find survival as tough as the plants do, so the local herbivores are going to eat pretty much anything green.  The alpine rose has responded by evolving a nasty cocktail of toxins, including the glycoside arbutin and the alkaloid arecoline, so even the hungriest of plant-eaters leave it alone.

[Image licensed under the Creative Commons MurielBendel, Rhododendron ferrugineum Valais4, CC BY-SA 4.0]

Well, most plant-eaters.  The current paper is about the discovery of a population of moths that have evolved to specialize on this plant.  It's the danger of an arms race; if one of the participants can exploit the adaptations of the other, it can actually end up better off.  Here, the moth has evolved tolerance to the alpine rose's toxins, and the result is it has a food source essentially to itself, with no competition.

The more the researchers looked into it, the more interesting the story got.  Not only had these moths evolved to specialize on eating alpine rose leaves, upon undergoing genetic analysis, they were shown to be conspecific with the species Lyonetia ledi, the Ledum leaf-miner moth.  This is a widespread species of moth that feeds mostly on the leaves of Labrador tea (Ledum palustre) and bog myrtle (Myrica gale).  This, however, left two puzzles: (1) most Ledum leaf-miners won't eat alpine rose; and (2) the nearest population of Ledum leaf-miners is over four hundred kilometers away.

What seems to have happened is that the moth, which feeds on plants that live in boggy areas at high altitude, was once more common -- during the last glacial period, when the favorable habitat was pretty much everywhere in Europe that wasn't actually covered in ice.  Then as things warmed up, the valleys became too warm for its host plants, and the range of both the plants and the moths moved upward in altitude, and broke up into patches.  One of them got isolated in the mountains of western Europe, where the alpine rose was way more common than either of the usual host plants for the species.  This created enormous selective pressure; as soon as there were moths that could at least tolerate the alpine rose's toxins, they were at such an advantage that they outcompeted their cousins and more or less took over.  Over time, this preference for alpine rose became a requirement.  Now, the moth feeds only on alpine rose -- something no other insect species can manage.

So that's today's cool science story; a poisonous flower and a relict population of moths stranded in the high mountains after the last glaciation.  Once again illustrating what Darwin meant by saying that evolution had created "many forms most beautiful and most wonderful" -- some of which are still out there waiting to be discovered.

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It's astonishing to see what the universe looks like on scales different from those we're used to.  The images of galaxies and quasars and (more recently) black holes are nothing short of awe-inspiring.  However, the microscopic realm is equally breathtaking -- which you'll find out as soon as you open the new book Micro Life: Miracles of the Microscopic World.

Assembled by a team at DK Publishers and the Smithsonian Institution, Micro Life is a compendium of photographs and artwork depicting the world of the very small, from single-celled organisms to individual fungus spores to nerve cells to the facets of a butterfly's eye.  Leafing through it generates a sense of wonder at the complexity of the microscopic, and its incredible beauty.  If you are a biology enthusiast -- or are looking for a gift for a friend who is -- this lovely book is a sure-fire winner.  You'll never look the same way at dust, pollen, algae, and a myriad of other things from the natural world that you thought you knew.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

The birds and the bees and the flowers and the trees

One of the most fascinating aspects of evolution, and one of the least appreciated (outside of the biology-nerd community, anyhow), is how insects and flowering plants have coevolved.

Coevolution occurs when two different species (or groups of species) reciprocally affect each other's evolutionary changes.  A commonly-cited example is the pair made up of cheetahs and impalas; the fastest cheetahs get more food than the slowest, and the slowest impalas get turned into food more than the fastest, so each species has a tendency to get faster and faster (at least until other considerations, like the limitations of physiology, kick in).  This specific type of coevolution is sometimes called an evolutionary arms race, and can occur not only with speed but with issues like toxicity (in the species being eaten) and toxin tolerance (in the species doing the eating).

The coevolutionary relationship between flowering plants and insects is a curious one.  Certainly, there are insects that eat (and damage, sometimes fatally) plants; witness the gypsy moths that this year have shredded trees in our part of New York state.  Fortunately for our apple and cherry trees and other susceptible species, most trees attacked by gypsy moths survive defoliation and are able to put out another set of leaves once the moths' caterpillars are gone, and because the moths are a "boom-and-bust" species, they seldom mount a serious infestation like this year's more than once a decade or so.

But there's a "nicer" side to coevolution between insects and flowering plants, and that has to do with pollination.  We all learned in elementary school how bees and butterflies pollinate flowers, but it's more complicated than that; insects and plants have in some senses opposite interests in pollination.  For insects, the more different species of flowers they can visit, the more potential nectar sources they can access; but that's actively bad for flowers, because if a bee visits (for example) a rose and then a clover blossom, any pollen transferred does the plant no good at all because the two species aren't cross-fertile.  That pollen is "wasted," from the plant's perspective.

A species peony from the Caucasus Mountains, Paeonia mlokosewitschii -- nicknamed "Molly-the Witch" because most people can't pronounce "mlokosewitschii" -- primarily pollinated by ants and wasps  [photo taken this spring in the author's garden]

Plants have adopted a variety of strategies for coping with this.  Some, such as wind-pollinated plants (oaks, maples, willows, grasses, and many others) produce huge amounts of pollen, because they don't have a carrier to bring it from one flower to the next, and much of the pollen never reaches its target.  (This is why wind-pollinated plants like ragweed are primary culprits in pollen allergies.)  The same thing is true of plants that are visited by many different kinds of pollinators, and for the same reasons.

But the other approach is specialization.  If a flower has a shape that fits the mouthparts of only one species of pollinator, the pollen picked up is almost certainly going to be transferred to a flower of the same species.  In stable ecosystems, like rainforests, there are flowers and pollinators that have coevolved together so long that both are completely dependent on the other -- the pollinator's mouthparts don't fit any other flower species, and the flower's shape isn't compatible with any other pollinator's mouthparts.

Anna's Hummingbird (Calypte anna) visiting Crocosmia flowers in San Francisco, California [Image licensed under the Creative Commons Brocken Inaglory, Humming flowers, CC BY-SA 3.0]

As my evolutionary biology professor put it, this strategy works great until it doesn't.  Specialists get hit hardest by ecological change -- all that has to happen is for one of the pair to decline sharply, and the other collapses as well.  Their specialization leaves them with few options if the situation shifts.

The topic comes up because of a paper this week in Biological Reviews that looks at plant species which try to do both at once -- attract various species of pollinators (increasing the likelihood that pollen gets widely distributed, and mitigating the damage if one species of pollinator disappears) while encouraging those pollinators to feed exclusively on the flowers of that species only (decreasing the likelihood that the pollen will be transferred to a flower of an unrelated species).

A trio of researchers -- Kazuharu Ohashi (of the University of Tsukuba), Andreas Jürgens (of Technishe Universität Darmstadt), and James Thompson (of the University of Toronto) found that this complicated "hedging your bets" strategy is more common than anyone realized.  Some of the solutions the plants happen on are positively inspired; the goat willow (Salix caprea) has evolved to be pollinated by two different pollinators, bees and moths -- and the flowers actually change scents, producing one set of esters (chemicals associated with floral fragrance) during the day, and a different one at night, to attract their diurnal and nocturnal visitors most efficiently.  Cardinal shrub (Weigela spp.) flowers change scent as they age -- young flowers have fragrances attracting bees and butterflies, older ones attracting species like drone flies.

"[Y]ou'd expect that flowers would mostly be visited by one particular group of pollinators," said study lead author Kazuharu Ohashi, in an interview with Science Daily.  "But flowers often host many different visitors at the same time and flowers appear to meet the needs of multiple visitors.  The question we wanted to answer is how this happens in nature... Most flowers are ecologically generalized and the assumption to date has been that this is a suboptimal solution.  But our findings suggest that interactions with multiple animals can actually be optimized by minimizing trade-offs in various ways, and such evolutionary processes may have enriched the diversity of flowers."

Evolution is more subtle than a lot of us realize, happening on solutions to ecological problems that nearly defy belief.  The bucket orchid of South America (Coryanthes spp.) has a flower with a complex "trap" that only appeals to one species of bee -- and is so convoluted that when I explained its function to my biology students, I had to assure them more than once that I wasn't making it all up to fool the gullible.  The strategies vary dramatically from species to species, but always fall back to that tried-and-true rule -- evolution is the "law of whatever works."

So there's something to think about when you're working in your garden.  The birds and the bees and the flowers and the trees are a lot more complicated and interconnected than they may seem.  Many of the sophisticated mechanisms they use to assure survival and reproduction are only coming to light now -- and papers like Ohashi et al. give us a new lens into how beautiful and intricate the natural world is.

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Most people define the word culture in human terms.  Language, music, laws, religion, and so on.

There is culture among other animals, however, perhaps less complex but just as fascinating.  Monkeys teach their young how to use tools.  Songbirds learn their songs from adults, they're not born knowing them -- and much like human language, if the song isn't learned during a critical window as they grow, then never become fluent.

Whales, parrots, crows, wolves... all have traditions handed down from previous generations and taught to the young.

All, therefore, have culture.

In Becoming Wild: How Animal Cultures Raise Families, Create Beauty, and Achieve Peace, ecologist and science writer Carl Safina will give you a lens into the cultures of non-human species that will leave you breathless -- and convinced that perhaps the divide between human and non-human isn't as deep and unbridgeable as it seems.  It's a beautiful, fascinating, and preconceived-notion-challenging book.  You'll never hear a coyote, see a crow fly past, or look at your pet dog the same way again.

[Note: if you purchase this book from the image/link below, part of the proceeds goes to support Skeptophilia!]