The dumbest science question ever?

From NASA/Wikimedia commons: The Hubble image shows the paired galaxies very close together with streams of stars being pulled out of the galaxies. The colliding "parent" galaxies lose their shape and smoother galaxies are formed. The whole merging process can take less than a billion years.

I don’t know if this qualifies as the dumbest science-related question ever, but it’s one that’s been bothering me for, oh, years. If you google it, the hits that turn up are, ironically, all religion related, and no help at all.

The question: Why was life such a hit? Rephrased: Why did life, once it got going, persist?

Maybe you know what I mean. Everywhere we look on Earth (almost), we find life. In places where you’d think nothing could evolve, much less survive. There are the bacteria living two miles deep in the Earth, the life flourishing in lava tubes, the organisms that surprised us in such inhospitable places as geothermal vents, Antarctic lakes, and yes, Mono Lake in California.

Why was life such a big hit once Nature got things going? In a more evolutionary context, what benefit do natural processes derive from life? Even after cataclysmic losses in mass extinctions, life bounces back.

Yes, of course, after those extinctions, niches were more readily available than a cheap foreclosure in Las Vegas. And of course, when life first arose, the world was one big niche just waiting to be partitioned. But why are there no boundaries on the blue planet? Hardly anywhere to go where life isn’t?

Like I said, this could be the dumbest science-based question ever asked. I’m assuming some kind of evolutionary context for life itself in the larger backdrop of the physical world, a world that evolves ever so inexorably to a universal heat death that our little minds (or maybe it’s my little mind) can scarcely encompass. Do life and its many processes get us there faster, urge entropy’s expansion? That, of course, assumes some ultimate, seemingly predetermined goal of transformation into heat and an ultimately messy demise.

That assumption may be and probably is a huge misstep. After all, the universe has got some pretty big transformation engines without turning to a teensy little mechanism like life. In other news, it would actually link the second law of thermodynamics and evolution directly, instead of leaving them as fodder for arguing creationist worldviews.

But it feels like a big question. The related question is, Is it a big, stupid question?

Did humans and their fire kill off Australia’s megafauna?

Genyornis. Courtesy of Michael Ströck & Wikimedia Commons.

Timeline, 2005: For those of us who do not live in Australia (and live instead in, say, boring old Texas), the animals that live on that continent can seem like some of the most exotic species in the world. The kangaroo, wombat, and Tasmanian devil, and most of all, the platypus, are high on the list of the unusual and bizarre in the animal kingdom.

But modern-day Australia has nothing on the Australia of 50,000 years ago when humans first arrived from Java. They encountered huge kangaroos, marsupial lions, 25-foot lizards, and tortoises the size of a subcompact car. Yet, within 5000 years, many of these animals had disappeared permanently. And since the dawn of the study of paleontology, researchers have wondered why.

Of course, it’s our fault

Of course, humans feature as the culprits in most scenarios. Just as the first people in the Americas are usually blamed at least in part for the disappearance of the American megafauna, like mammoths or giant sloths, the first people in Australia have also been suspected of hunting these animals to extinction or exposing them to diseases that decimated the populations.

As it turns out, humans may be to blame, but not through direct destruction or disease transmission. Instead, it may be the mastery of fire, the turning point in our cultural history, that ended in the extinction of many species larger than 100 pounds on the Australian continent.


Australia’s first people probably set huge fires to signal to one another, flush animals for hunting, clear paths through what was once a mosaic of trees, shrubs, and grasses, or to encourage the growth of specific plants. The byproduct of all of this burning was catastrophic to the larger species on the continent.

The fires, according to one study, wiped out the drought-adapted plants that covered the continent’s interior, leaving behind a desert of scrub brush. The change in plant cover may have resulted in a decrease in water vapor exchange between the earth and the atmosphere with the ultimate effect of ending the yearly monsoon rains that would quench the region. Without the rains, only the hardiest, desert-ready plants survived.

You are what you eat…or ate

How could researchers possibly have elucidated these events of 45,000 years ago? By looking at fossilized bird eggs and wombat teeth. Using isotopic techniques, they assessed the types of carbon present in the bird eggs and teeth that dated back from 150,000 to 45,000 years ago. These animals genuinely were what they ate in some ways, with some isotopic markers of their diet accumulating in these tissues. Because plants metabolize different forms of carbon in different ways, the researchers could link the type of carbon isotopes they found in the egg and teeth fossils to the diet of these animals.

They found that the diet of a now-extinct species of bird, the Genyornis, consisted of the nutritious grasses of the pre-human Australian landscape. Emu eggs from before 50,000 years ago pointed to a similar diet, but eggs from 45,000 years ago indicated a shift in emu diet from nutritious grasses to the desert trees and shrubs of the current Australian interior. The vegetarian wombats also appear to have made a similar change in their diets around the same time.

Or, maybe not

And the species that are still here today, like the emu and the wombat, are the species that were general enough in their dietary needs to make the shift. The Genyornis went the way of the mammoth, possibly because its needs were too specialized for it to shift easily to a different diet. Its teeth showed no change in diet over the time period.

The researchers analyzed 1500 fossilized eggshell specimens from Genyornis and emu to solve this mystery and to pinpoint human burning practices as the culprits in the disappearance of these megafauna in a few thousand brief years. Today’s aboriginal Australians still use burning in following traditional practices, but by this time, the ecosystems have had thousands of years to adapt to burns. Thus, we don’t expect to see further dramatic disappearances of Australian fauna as a result of these practices. Indeed, some later researchers have taken issue with the idea that fire drove these changes in the first place, with some blaming hunting again, and as with many things paleontological, the precise facts of the situation remain…lost in the smoky haze of deep history.

Complex amphibian responses to past climate change

Eastern tiger salamander: Ambystoma tigrinum, courtesy of Wikimedia Commons

We were like gophers, but now we’re like voles

Timeline, 2005: There is a cave in Yellowstone packed with fossils from the late Holocene, from about 3000 years ago. We can glean from this trove of stony bone how different taxa respond to climate change at the morphological and genetic levels and define and make predictions about the current response of the world to such changes.

The cave, which is in a sensitive area of the park off limits to visitors, houses the fossilized bones of rodents, wolves, amphibians, bears, coyotes, beavers, and elk, among others. This fossil cornucopia has yielded so much in the way of stony evidence that sorting it all is in itself a mammoth task. But two climatic stories have emerged from the samples it has yielded.

A global warming story…from the Middle Ages

The first story is about salamanders and climate change. No, it’s not a 21st-century story about global warming, but a Middle Ages story about a hotter planet. From about 1150 to 650 years ago, the earth underwent a brief warming period known as the Medieval Warming Period. During this time, the sea surface temperature was about a degree warmer and overall, the planet was much drier. This climatic anomaly was followed by what many climatologists call the Little Ice Age, a period that ended around 1900.

During the warm and dry period, animals in what would become Yellowstone National Park responded in ways that left clues about how animals may respond today to our warming planet. Amphibians make particularly sensitive sentinels of environmental change, alerting us to the presence of pollutants or other alterations that affect them before larger manifestations are detectable. And they even provide us evidence in their fossils.

Hot times, smaller paedomorphic salamanders

A group from Stanford excavated the fossils of Ambystoma tigrinum (the tiger salamander) from 15 layers at the Yellowstone site and divided them into five time periods based on their estimated age. They then divided the fossils again based on whether they represented the tiger salamander in its larval, paedomorphic, early adult, or later adult stages. The tiger salamander exhibits paedomorphism, in which the animal achieves reproductive capacity or adulthood while still retaining juvenile characteristics. In the case of the tiger salamander, this translates into remaining in the water, rather than becoming a terrestrial adult, and into retaining characteristics like frilly gills. The molecular determinant of whether or not an amphibian undergoes complete metamorphosis from juvenile to adult is thyroid hormone; when levels of this internal signal are low, the animal will remain juvenile.

The researchers found that during the medieval warming period, the paedomorphic salamanders became smaller than they were during cooler times. This outcome would be expected because when water is cooler, thyroid hormone levels will be lower, and the animal will continue growing as a juvenile.

Hot times, larger adult salamanders

On the other hand, the terrestrial adult salamanders were much larger during the warm period than during cooler periods. Again, this outcome would be expected because the heat on land would encourage faster metabolism, which would result in faster growth. The researchers found no difference in actual numbers between groups at cool vs. warm periods, but express concern that drying in Yellowstone today as a result of global warming might reduce the number of aquatic paedomorphs, affecting aquatic food webs.

From amphibians to gopher teeth

The same group also studied DNA from fossilized teeth of gophers and voles discovered in the cave. They found that during the dry period, gophers, who were stuck underground and isolated, experienced genetic bottlenecking, a reduction in diversity that persists today. However, the mobile, above-ground voles sought mates far and wide during the dry, warm period and actually experienced an increase in diversity. The lead researcher in the group compares early groups of isolated humans to the gophers, saying that they would have experienced a loss of diversity. But today’s population, with our ability to travel the globe with ease, is probably undergoing an increase in diversity since we’re able to mate with people a hemisphere away.

Placoderms had the "fun kind" of sex

Dunkleosteus, a Devonian placoderm. Pencil drawing, digital coloring, Nobu Tamura, Obtained from Wikimedia Commons.

Timeline, 2008: From about 420 to 350 million years ago, the rulers of Earth’s seas were an unattractive-looking armored fish known today as the placoderms. This group, consisting of many species, were the bulldogs of the fish world, heavy-bodied with big ugly mouths full of protruding, potentially dangerous bony plates. Some of them were quite small, but a few species grew as large as 20 feet in length. They were the dominant vertebrate worldwide for about 70 million years.

Conventional scientific wisdom would say that these ancient fish reproduced the way modern representatives of ancient lineages do: external fertilization, the sperm fertilizing the egg with a little help from water. The wisdom was so conventional, in fact, that experts placed the rise of internal fertilization—delivery of the sperm into the female via an act of copulation—a good 200 million years after the placoderms swam the seas.

A catastrophe on the reef

In what is now Western Australia, something terrible happened about 380 million years ago in the shallow seas covering a coral reef: the oxygen that fed the reef suddenly plummeted, leaving the coral starved and unable to support the food web built around it. The outcome was a rapid, catastrophic loss of all of the species on the reef, including the placoderms. Thanks to stable plate tectonics and some good sediment coverage, these hapless animals remained preserved for the subsequent millions of years until a team of fossil hunters uncovered them. They now populate one of the most famous fossil finds in the world, the Gogo fossil sites, which are packed with perfect specimens of long-lost species.

The role of Sir David Attenborough, the world’s coolest naturalist

Among those perfect specimens—so perfect, in fact, that three-dimensional samples are available—is a species that now has the name Materpiscis attenboroughi. The name means “Attenborough’s mother fish” and requires a bit of explanation. Back in the late 1970s, Sir David Attenborough produced a wonderful nature and science series called Life on Earth. In the series, he highlighted the Gogo sites, and his interest led researchers to name the fish after him. But the first part of the name, the genus name Materpiscis, means “Mother fish.” Why? Because when this 10-inch fish died during that catastrophic reef loss, she died just before becoming a mother.

We know this because a couple of researchers working on her fossilized remains decided at the last minute to expose the fossil to one more round of acid treatment. They had pretty much decided to write her up as she was, which would have been plenty because of the preserved 3D perfection of her remains. But they agreed to that last treatment, which gently etches away layers of the fossil to reveal what lies beneath. They are glad they did, because what that last treatment exposed, inside of the adult fish, is a tiny, fossilized fish embryo, about a quarter of the size of its mother.

Eureka! Again, and again, and again

Anyone looking at that embryo, inside of that fish, might have had any number of “Eureka” thoughts in that moment. Eureka! It’s a fish embryo, 380 million years old! There aren’t that many of those lying around. But even more important, Eureka! It’s a fish embryo inside of the mother. That means that the egg was fertilized inside of the mother, where the embryo grew, nourished in her body, just as mammals do it. The embryo was even attached by a tiny, fossilized umbilical cord. A final Eureka! just might be that we can confirm the sex of this fish just based on the fact that she was pregnant when she died.

This just in: Sex is fun

The presence of an internally developing embryo in this placoderm sets the assumed evolutionary timing of internal fertilization back about 200 million years. No one would have guessed that these ancient, armored bulldog-like fish would represent the earliest-known internal fertilization. And the fact that fertilization was internal means that these animals must have copulated, the standard mechanism for getting sperm into the female to meet the egg. That recognition led one of the embryo’s discoverers to remark that this animal represents the earliest example a species engaging in “sex that was fun.”

Giant Mesozoic badger turned mammalian dogma on its head

Juvenile badger with dinosaur dinner

Check your biology book. If it says anything about mammals during the age of dinosaurs, it probably depicts the mammals as small, shrew-like animals scuttering around at night, barely scratching out a living as they scurry away from the thudding feet of a Tyrannosaurus rex.

Mammals ate dinosaurs–tasted like chicken

Banish the thought and rewrite the book. Yes, many of the mammals that lived in the Mesozoic—from about 248 to 65 million years ago—were shrew- or rat-like critters that probably stayed out of the way of most dinosaurs. But recent fossil finds demonstrate that some of the mammals in the age of the dinosaur not only got in the path of dinosaurs, they ate them.

In China, there is a famous fossil bed best known for the fossils of feathered dinosaurs it has yielded. But paleontologists have also turned up some other intriguing remnants, among them the mineralized bones of species from the Repenomamus genus. These animals were long, squat-bodied creatures with strong jaws and very sharp, pointy teeth. Researchers at the site had already reported finding R. robustus, a carnivorous mammal weighing in at about 15 pounds.

Giganticus, indeed

But two other finds reported in Nature flip common Mesozoic mammal dogma upside down. The first discovery was that of a fossil species now dubbed Repenomamus giganticus, a cousin of R. robustus, but with some distinctive features: this specimen probably weighed about 30 pounds and grew to be up to a meter long. Think about a mid-sized dog, say a large basset hound, with a badger-like face and rodent-like sharp teeth, and you’ve got your R. giganticus. Not something you’d want to go hand-to-tooth with when it’s in a bad mood.

Died with dinner inside (& more dog breed comparisons)

That, at least, is what researchers concluded after their second find: a fossil of R. robustus, the smaller species, with a juvenile dinosaur skeleton where the R. robustus stomach would have been. Not only did these hardy Repenomamus species look scary, for juvenile, leaf-eating dinosaurs, they were deadly. Experts estimate, based on mammalian habits of today, that mammals can kill and consume prey that is up to half of their body weight. If R. robustus could snack on a 5-inch dinosaur baby, then presumably R. giganticus could have put back a dinosaur the size of a dachshund.

The scientists who identified and named R. giganticus had a couple of hurdles to overcome. First, they had to determine that this was a genuine average version of R. giganticus, not simply R. robustus with a pituitary problem. The error that would result would be akin to finding the skeleton of the world’s tallest man and assuming that it represented our entire species.

Badger or human, your teeth show your age

But they looked at the teeth that accompanied the skull and jaw fossils, and the molars held the clues to the animal’s age at death. The last molar of the lower jaw appeared to have just erupted when the animal died, and it had little wear. Based on this clue, the researchers concluded that fossilized remains were from a juvenile representative of the new R. giganticus species.

Making the case that a Mesozoic mammal had actually consumed a dinosaur also required some consideration and discarding of various possibilities. The little dinosaur skeleton, from a Psittacosaurus, was a small patch of bones within the ribcage of some R. robustus fossil remains. The bones were located right where the stomach is on today’s mammals, and appeared to have been broken, torn apart, and displaced from one another. The fossil bones of the accompanying R. robustus skeleton were not in this condition. The Psittacosaurus specimen also had teeth, most of which were worn, implying that this animal was not scavenged from an egg as an embryo. Based on these clues, the researchers concluded that this R. robustus had caught and eaten the hapless Psittacosaurus—dismembering it and swallowing it in chunks—shortly before meeting its own death.

Has the ivory-billed woodpecker left the building?

Watercolor painting of ivory-billed woodpeckers from Audubon's Birds of America, 1826.

Imagine waking up one morning to real film footage of a duckbill dinosaur wandering around the Great Plains. Your reaction might be similar to that of birders around the world when Science magazine reported in 2005 that the ivory-billed woodpecker, thought for 60 years to have been extinct in the United States, still existed.

A forest bird of legend

The woodpecker entered birder and ecologist lore when its numbers declined in the early part of the 20th century. Its habitat was bottomland forest in the southeastern United States and Cuba, and its niche included drilling into mature trees. When people came along, logging away the woodpeckers’ homes, the bird appeared to vanish. By the 1920s, we thought it had disappeared forever, although in 1943, there was a single confirmed sighting of a lone female, flying over the stumps of an old-growth forest. She became a central figure in a PhD thesis in 1944. Then for 60 years, silence.

False calls

Well, not complete silence. There were many reports of sightings, but most were traced to another woodpecker species, the pileated woodpecker. The ivory-billed woodpecker differs distinctly from its pileated cousin in beak color, in having white patches on its back when perched, and in its size and the solid-black crest of the female. It has a three-foot wing span, which is huge for a woodpecker, and can grow as large as 20 inches long. It is a big, beautiful, and surprising bird, with a bright red crest on the males that must be startling to see among the cypress of a bottomland forest.

A mesmerizing obsession

Birders, possibly the most obsessive of any taxon fan club, had long wandered into the swampy bottomlands of Arkansas and Louisiana, trying to find ivory-billed woodpeckers. There was a confirmed sighting in Cuba in the ‘80s, and over the decades, people have claimed sightings or reported having heard the ivory-billed’s call. Professionals and amateurs alike have waded among snakes and fought off bugs, playing tapes of the call and listening for a response. At one point, searchers found a nest that had an ivory-billed look to it and trained a remote-sensing camera on it, but saw nothing.

And then in 1999, a kayaker thought that he had seen a pair of the birds. His report received serious attention from the government, local papers, and academic groups interested in the woodpecker both for its inherent beauty and for its status as a symbol of the price of our destructive tendencies. Soon, the old forests of the southeast were crawling with ornithologists, all hoping to catch a glimpse, take a picture, and emerge with definitive proof that a bird long thought to be extinct had survived.

The beat of the forest, revived?

Some people heard the drumming sounds the woodpecker is known to make. A handful of people who really knew their woodpeckers reported sightings. But it was a four-second video of the shy, reclusive bird that clinched it. The video is short and blurry, taken from a kayak in late April of 2004 on a camcorder. But even its poor quality couldn’t hide the distinctive markings and features of the ivory-billed woodpecker.

The confirmation set the world of ornithology astir, but it also reverberates among ecologists and environmentalists. The fact that at least one male ivory-billed woodpecker exists indicates that at least one breeding pair must have survived into the 1990s because the birds live 15 to 20 years at most. And it also might have meant a second chance for us and the woodpecker. Unfortunately, according to a recent report from Cornell researchers who have spent five years looking for more signs of the bird, “it’s unlikely that there are recoverable populations” of the bird where they’ve been searching.

Did division of labor defeat the Neanderthals?

According to some anthropologists, the classic depiction of Paleolithic man as a few strapping cavemen ganging up on a mammoth with their spears might need to be replaced with dioramas of women gathering seeds or a man scraping an animal carcass from the ground to take home for dinner. In addition, this division of labor between men and women may have given Homo sapiens the upper hand when it came to their competition with Neanderthals in the Upper Paleolithic, about 45,000 to 10,000 years ago.

You may be familiar with some of the usual reasons proposed for the extinction of the Neanderthals and the supremacy of H. sapiens in the competition for resources: The wily H. sapiens swarmed the Neanderthals, defeating them in war with superior weaponry or a greater ability to resist disease or defy climate change. Some experts have proposed that a combination of these climatological and cultural factors may have contributed to the Neanderthal’s loss. But until now, no one had focused on differences in division of labor as giving H. sapiens the advantage.

The crushing hand of the Neanderthal woman

Evidence shows that Neanderthal men and women may have shared similar robust builds. In addition to bone finds that suggest as much, a researcher who focuses on hand mechanics has found that the Neanderthal female hand could exert as much force as that of a male. In addition, Neanderthal home sites rarely include artifacts such as tools for grinding seeds or trapping small animals, or even evidence of clothing production, such as needles. Thus, it seems that the Neanderthals may have, as a group—men, women, and children—spent their time focusing on one thing: big game.

Hunting a large animal that has defense ranging from tooth to antler to hoof to claw is a dangerous business, more so when your only weapon is a pointed stone attached to the end of a stick. Neanderthals got a big payoff when their spears worked, however, in the form of calorie- and protein-rich meat for the group. Evidence suggests that the whole group participated in this dangerous task—the bones of females as well as males bear the signs of many fractures, possibly the result of this dangerous lifestyle. Women and children may have been responsible for driving game or forging escape routes should the angered and frightened animal have turned on the group.

The pitfalls of group big-game hunting

This focus on a single kind of food source can have predictable consequences. In times of scarcity, the Neanderthals lacked other options. If they had no training or skills to obtain other food sources, then scarce big game translated into scarce Neanderthals. Homo sapiens, on the other hand, may have developed a division of labor between men and women before emerging from Africa 150,000 years after the Neanderthals, equipped with women who knew how to make protective clothing, trap small animals, and collect and prepare seeds and vegetation, and men with advanced weaponry who could efficiently hunt game. In addition, these people may have relied on scavenging as well as hunting to boost their food supply.

Division of labor gave H. sapiens the upper (non-crushing) hand?

The division of labor, which in some societies was reversed or not allocated in the same way between men and women, allowed Homo sapiens to adjust when food was scarce and boom when food was plentiful, or so some researchers now argue. These archaic humans could use their clothes-making skills to handle climate change and their efficient allocation of time resources to bring in food simultaneously from different sources, even when times were tough. Their booming population may have given them the numbers they needed to outcompete the Neanderthals.

…Or maybe not

Some researchers disagree with this hypothesis, suggesting that evidence of a division of labor dates back one or two million years, and there have been some predictable references in the news media to men’s and women’s roles today. One of the authors of the “division of labor” study explicitly cautions that what was beneficial 40,000 years ago isn’t necessarily a guide to what is beneficial today. Traits that provide a competitive edge are after all entirely reliant on context: What’s good in one environment may not necessarily be that helpful in a different set of circumstances.


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