Strange relations and island continents

56.2-53.2 Mya

We’re now in the Cenozoic era – our era. The transition from Paleocene to Eocene epochs in the early Cenozoic (55.9 million years ago) saw a spike in CO2 levels and a sharp rise in temperatures that lasted for several hundred thousand years – perhaps an analog for even more rapid human-caused global warming in our own time. (A recent review is here.)

We’ve seen a great many catastrophes in the history of life, and been reminded of the role of sheer chance in evolution. But the Cenozoic also sees a dramatic adaptive radiation and the steady progress of arms races among survivors of the great dinosaur die-off. Four large scale groupings of placental mammals have already appeared: Afrotheres (aardvarks, hyraxes, elephants, and sea cows), Xenarthrans (anteaters, armadillos, and sloths), Laurasiatheres (shrews, hedgehogs, pangolins, bats, whales, hoofed animals, and carnivores), and Supraprimates (aka Euarchontoglires, including rodents, tree shrews, and primates). This grouping of mammals is anything but obvious – it’s only with DNA sequencing that it has emerged. What’s noticeable is the association with different continents: Afrotheres with Africa, Xenarthrans with South America, and the others with the monster content of Laurasia (Eurasia and North America). Looking beyond placental mammals we see other continental associations: marsupials flourish in South America and Australia, and giant flightless “terror birds” carry on rather like predatory dinosaurs in South America.

There is a pattern here. Evolutionary arms races are most intense in the supercontinent of Laurasia (eventually joined by India and Africa). The island continents of South America and Australia stand apart, and they fare poorly when they start exchanging fauna with the rest of the world. We’ll see a similar pattern – large areas stimulate more competition, and more intense evolution, isolated areas are at a disadvantage – when we start looking at human history. (This is a major theme of Diamond’s deservedly popular Guns, Germs, and Steel.)

Paging Dr. Evil

We aren’t likely to collide with another Chicxulub-size asteroid any time soon, but even a smaller impact could be devastating. This is one argument for developing space travel. If we detected a meteor on a collision path with Earth, we could send a spaceship to nudge it out of the way. But there is always the Dark Side of the Force to reckon with …

Suppose you are a space entrepreneur, dedicated to harnessing the resources of the asteroids. You plan to mine them for their platinum group metals, valuable here on Earth, and for water and other volatiles, valuable for fuel and provisions in orbit. This is an expensive proposition, and it’s not clear that you’ll make a profit. But there is another business model. If you can direct asteroids away from Earth, and/or into Earth orbit, you can also direct them to collide with Earth. You can see where this is going: once an asteroid has been “accidentally” set on a collision course, you can charge a lot of money — a round trillion, say — to deflect it. In other words, “Nice planet you’ve got here. Too bad if anything was to happen to it.” Protection rackets are common enough in human history, and probably the cause of more suffering than all geological cataclysms – earthquakes, volcanoes, tsunamis, etc – put together. Who’s to say they won’t be part of our future too?

In case any lawyers from Planetary Resources: The Asteroid Mining Company are reading this, I should make 100% clear that I don’t seriously think any of today’s space entrepreneurs are planning anything like this, or could get away with it even if they wanted to. But it does suggest the gloomy thought that space faring and space colonization – touted by no less than Steven Hawking as an insurance plan against extinction – might actually reduce our species’ life expectancy rather than increasing it, at least until we get from interplanetary to interstellar settlement.

(Commenter sglover noted last year that “Walter Jon Williams wrote a noirish dystopia — “Hardwired” — with this premise.”)

dr.evil

“It’s Dr. Evil, I didn’t spend six years in Evil Medical School to be called ‘mister,’ thank you very much.”

The last of (most of) the dinosaurs

The end-Cretaceous extinction isn’t the biggest ever, but it’s the one everybody knows about. The Disney movie Fantasia (1940) did a version of the event, set to Stravinsky (and mixing up Jurassic and Cretaceous dinosaurs). In Terence Malik’s movie The Tree of Life, a predatory dinosaur discovers compassion in an encounter with a hadrosaur just before all their kind are wiped out by an asteroid: mass extinction meets the Book of Job.

The discovery that dinosaurs (and about 70% of all species in total) probably went extinct as a result of an extraterrestrial impact did more than anything else to bolster catastrophism. For most of the history of modern geology, geologists have mostly argued instead for uniformitarianism: the same slow processes we see today caused past geological and evolutionary changes. When evidence for an impact was first discovered – a thin layer of iridium, presumably extraterrestrial — paleontologists were pretty uniformly hostile: no physicist was going to tell them how to do science. But by now the evidence is overwhelming that the asteroid impact that left the Chixculub crater, in what is now the Yucatan, was largely responsible for the end-Cretaceous extinctions (although the volcanic eruptions that created the Deccan traps in India may also have played a role).

But at the same time that evidence has increasingly vindicated the catastrophist position, new discoveries in paleontology have increasingly brought home that one group of dinosaurs survived the extinction. Most people think of birds and dinosaurs as two quite distinct kinds of animal. But birds are just as much dinosaurs as bats are mammals. Many dinosaurs had many of the distinctive features of birds – warm-bloodedness and high metabolic rates (probably), wishbones, an advanced respiratory system, feathers (sometimes brightly colored, sometimes used for courtship), and parental care for nests of eggs and juveniles. It’s even possible that some flightless dinosaurs, like the turkey-sized Caudipteryx, were secondarily flightless, descended from flying ancestors like Archeopteryx. We don’t have to hope for The Lost World or Jurassic Park to come true to see living dinosaurs; a trip to the park, with The Sibley Guide to Birds in hand, will do it.

Leaves of grass

Not as dramatic as the evolution of Triceratops, Tarchea giganta, or T. rex, but of more lasting consequence, is the evolution of grasses (Poaceae). We know from coprolites – fossil feces — that grass was around by the Late Cretaceous, so the coevolution of grass and grazers had already begun with dinosaurs. These early grasses were not widespread. It would take climate shifts and more evolution (toward using carbon dioxide more efficiently) to create the sort of grasslands we are familiar with.

Grasses have played a central role in human evolution and human history. Human beings evolved in tropical grasslands, and some evolutionary psychologists think we still have an instinctive affinity for this environment. The domestication of grasses (wheat, barley, oats, millet, rice, corn) was one of the great revolutions in human prehistory, and grasses provided most of the calories people ate for most of recorded history. Contact along the frontier between grasslands supporting pastoralists and grain growing lands supporting peasants is one of the great engines of historical dynamics.

Grasses grow from the base of the leaf, not the tip of the stem, which is what allows them to recover from being grazed. This makes them a recurring symbol both of the transitoriness of life (“All flesh is grass, and all the goodliness thereof is like the flower of the field,” Isaiah 40:6) and its resilience.

The most famous poem about grass, by Walt Whitman, perhaps strikes the right elegiac note for the dinosaurs, who meet their doom tomorrow:

A child said, What is the grass? fetching it to me
with full hands;
How could I answer the child?. . . .I do not know what it
is any more than he.

I guess it must be the flag of my disposition, out of hopeful
green stuff woven.
Or I guess it is the handkerchief of the Lord,
A scented gift and remembrancer designedly dropped,
Bearing the owner’s name someway in the corners, that we
may see and remark, and say Whose?

Or I guess the grass is itself a child. . . .the produced babe
of the vegetation.

Or I guess it is a uniform hieroglyphic,
And it means, Sprouting alike in broad zones and narrow
zones,
Growing among black folks as among white,
Kanuck, Tuckahoe, Congressman, Cuff, I give them the
same, I receive them the same.

And now it seems to me the beautiful uncut hair of graves.
Tenderly will I use you curling grass,
It may be you transpire from the breasts of young men,
It may be if I had known them I would have loved them;
It may be you are from old people and from women, and
from offspring taken soon out of their mother’s laps,
And here you are the mother’s laps.

This grass is very dark to be from the white heads of old
mothers,
Darker than the colorless beards of old men,
Dark to come from under the faint red roofs of mouths.

O I perceive after all so many uttering tongues!
And I perceive they do not come from the roofs of mouths
for nothing.

I wish I could translate the hints about the dead young men
and women,
And the hints about old men and mothers, and the offspring
taken soon out of their laps.

What do you think has become of the young and old men?
What do you think has become of the women and
children?

They are alive and well somewhere;
The smallest sprouts show there is really no death,
And if ever there was it led forward life, and does not wait
at the end to arrest it,
And ceased the moment life appeared.

All goes onward and outward. . . .and nothing collapses,
And to die is different from what any one supposed, and
luckier.

Griffinoceratops

Blog about dinosaurs and you also end up blogging about the great age of dinosaur discovery that began almost 200 years ago. But dinosaurs hunting didn’t begin with the Victorians. Adrienne Mayor wrote a great book called The First Fossil Hunters, about how many of the monsters of ancient Greek and Roman myth were based on the discovery of the bones of extinct species, from mammoths (likely basis for the legend of Cyclops) to dinosaurs.

The griffin is a fine example. The Greeks from the 7th century BCE picked up stories from the Scythian nomads of the Eurasian steppe about griffins far to the east who guarded treasures of gold. These griffins were supposed to be “four-legged birds” with feathers, wings, eagle-like beaks, and clawed feet. The legendary homeland of the griffins was explored in 1922 by the great fossil-hunting expedition of Ray Chapman Andrews, which discovered abundant remains of the late Cretaceous (about 83 million years ago) Protoceratops, along with dinosaur eggs. The resemblance to the legendary griffins is striking.

griffinceratops copy

Mayor argues that Scythian discoveries of ceratopsian skeletons inspired the story of the griffin. The main difference is the griffin’s wings, which might have been a misreading of ceratopsian collar bones. Remarkably, the ancient idea of the griffin is close to recent reconstructions of feathered agile dinosaurs. The word “dinosaur” literally means “terrible lizard,” but many dinosaurs really were closer to “four-legged birds.”

Dino habilis

When Jane Goodall reported in 1960 that chimpanzees at her field site in Gombe, Tanzania, were making tools, she made headlines. The discovery toppled a supposed pillar of human uniqueness, enshrined in the catchphrase “Man the Toolmaker.” Louis Leakey, upon getting the news from a telegram sent by Goodall, wrote “Now we must redefine tool, redefine Man, or accept chimpanzees as humans.”

We’ve grown more blasé since then, and the gradually accumulating evidence for dinosaur tool use has attracted a lot less attention. The evidence is similar to what we find for early human ancestors, Homo habilis and earlier. It takes the form of manuports, stones that have been transported a long way out of their geological context. Although the inference was resisted at first, it now looks almost certain that they were picked up and carried, probably by dinosaurs who used them as hammers to smash bones (or, less plausibly, to attract mates). Most suspected manuports weigh just a few pounds (a kilogram or two), and the most likely tool users in this case are the various raptors. A small fraction of manuports are much larger – up to fifty pounds (over twenty kilograms) – and may have been carried by larger dinosaurs like Tyrannosaurus rex. T. rex was clearly a carnivore, but people have long wondered how she got her meat, whether by hunting or scavenging. The latest finds raise the possibility that she was a specialized predator, dropping rocks from above to smash armored prey like tortoises and ankylosaurs.

Tool use is sometimes taken as evidence of sophisticated cognition. With dinosaurs, however, we may be seeing something different, the evolution of complex tool-using instincts over many tens of millions of years, no more indicative of high intelligence than honeybee dances or spider webs. If there is a parallel with human evolution it is not that dinosaurs were especially smart, but that the process of evolution, given as a starting point a pair of forelimbs not being used for locomotion, is likely to find (or exapt) some new function for them.

The suggested evolutionary scenario for instinctive tool use in dinosaurs is supported by findings regarding another group of organisms, still abundant today: ethologists discovered decades ago that complex tool using abilities without a high level of intelligence are present among some varieties of gull. More recently, these gull abilities have turned out to be widespread.

Consider her ways

104-98.6 million years ago

There are some pieces of paleontology that really stand out in the popular imagination. Dinosaurs are so cool that even if they hadn’t existed we would have invented them. (Maybe we did, in the form of dragons. And tune in early April for the dinosaur-griffin connection.) Also, as I suggested in the preceding post, transitions from one form of locomotion to another – flightless dinosaurs to birds, fish to tetrapods, land mammals to whales – really grab the imagination (and annoy creationists) because the largest and most distinctive named folk categories of animals (snakes, fish, birds) are built around modes of locomotion.

Evolutionary biologists tend to see things differently. Turning fins into legs, legs into wings, and legs back into flippers is pretty impressive. But the really major evolutionary transitions involve the evolution of whole new levels of organization: the origin of the eukaryotic cell, for example, and the origin of multicellular life. From this perspective, the really huge change in the Mesozoic – sometimes called the Age of Dinosaurs – is the origin of eusociality among insects like ants and bees. An ant nest or a bee hive is something like a single superorganism. with most of its members sterile workers striving – even committing suicide — for the colony’s reproduction, not their own. (100 million years ago – corresponding to March 29 in Logarithmic History — is when we find the first bee and ant fossils, but the transition must have been underway before that time.)

Certainly the statistics on social insects today are impressive.

The twenty thousand known species of eusocial insects, mostly ants, bees, wasps and termites, account for only 2 percent of the approximately one million known species of insects. Yet this tiny minority of species dominate the rest of the insects in their numbers, their weight, and their impact on the environment. As humans are to vertebrate animals, the eusocial insects are to the far vaster world of invertebrate animals. … In one Amazon site, two German researchers … found that ants and termites together compose almost two-thirds of the weight of all the insects. Eusocial bees and wasps added another tenth. Ants alone weighed four times more than all the terrestrial vertebrates – that is, mammals, birds, reptiles, and amphibians combined. E. O. Wilson pp 110-113

E. O. Wilson, world’s foremost authority on ants, and one of the founders of sociobiology, thinks that the origin of insect eusociality might have lessons for another major evolutionary transition, the origin of humans (and of human language, technology, culture, and complex social organization). In his book The Social Conquest of Earth he argues that a key step in both sets of transitions was the development of a valuable and defensible home – in the case of humans, a hearth site.

One trait found in both ants and humans is large-scale warfare. Wilson gives an idea of the nature of ant warfare in fictional form in his novel Anthill. It’s an interesting experiment, but also disorienting. Because individual recognition is not important for ants, his story of the destruction of an ant colony reads like the Iliad with all the personal names taken out. But Homer’s heroes fought for “aphthiton kleos,” undying fame (and got some measure of it in Homer’s poem). The moral economy of reputation puts human cooperation in war and peace on a very different footing from insect eusociality.

Consider her ways” is the title of a short story by John Wyndham, about a woman from the present trapped in a future ant-like all-female dystopia. It was made into an episode of Alfred Hitchcock Presents. The title is from Proverbs 6:6, “Go to the ant, thou sluggard, consider her ways and be wise.”