27 February 2009

Psychedelica, the bouncing fish

Recently discovered


Armand Leroi makes a compelling (although very broadbrush) presentation of the thesis that all human music is ultimately related and that its common roots may be traced, just as those of language or our shared genetic inheritance can be. The thesis resonates intuitively. But Leroi has actual statistical evidence .

Something similar obtains in whales (blue, humpback).

The flowers appear on the earth; the time of the singing of birds is come.

Could human music reach far beyond earth (with, say, Berg's Über die Grenzen des All as one kind of early prototype)?

26 February 2009

Hunters and hunted

This post follows a few traces from traditional aboriginal whaling and its echoes. [1]
Bowheads are among the longest lived animals: Nalutaliq, a white-headed bowhead, has been sighted off Baffin Island for more than a hundred years. In 1995 a crew of Iñupiat whalers from Wainwright, Alaska, found two stone harpoon blades in the blubber of a whale they were butchering. Stone points had not been used for more than a century -- not since commercial whalers brought metal tools to the Arctic and traded them to the natives. [2]
A favoured hunting craft was the Baidarka, "a living vessel whose skin caressed the shape of the waves." [3] But in the hunt for the whale, the bodies of smaller animals could become vessels of death:
In some hunts, the bladders of narwhals, walruses and seals were used as floats to the harpoon. Sometimes entire seals, skinned through the mouth with all orifices and wounds sewn shut, were used as drogues. Inflated through a bone tube, each seal float created a drag of about 100kg, exhausting the whale and reducing its chance of escape.
In Inuit mythology, Agloolik, a spirit that lives underneath the ice, gives aid to fishermen and hunters.

Another spirit, Wentshukumishiteu, sometimes terrifies the hunters away:
The Innu say [this] evil creature...is able to travel anywhere on the water and under the water and it is able to break through the ice. It can also travel under the ground and through rocks.
Joe Roman continues:
After the whale was killed, the biggest challenge was the tiresome chore of towing the enormous quarry ashore. Nuu-chah-nulth whalers employed charms...; some tied hummingbirds to the line, others turtles.
A chant from south-west Alaska contains this:
You are dying but your death will no be forgotten.
We will strip your bones of flesh, but we will send them back to the sea
that you may live again, so fear not.
Following a sucessful hunt, writes Roman, communities from Kamchatka to Vancouver Island had a period of ritual mourning of about three days, as long as that for a man.


[1] Aboriginal whaling continues today, but with modern tools. This post follows an earlier one which refers to early modern European hunting of the bowhead.

[2] Joe Roman, citing John J. Burns in the Encyclopedia of Marine Mammals (2002)

[3] The anthropologist Margaret Lantis, notes Roman, suggested that a whale hunting cult extended from Kamchatka to Hudson Bay, and from Point Barrow, Alaska to the coast of Washington State. The cult may even have extended as far as Japan and Greenland (The Alaskan Whale Cult and its Affinities, 1938). According to T. T. Waterman (1920), the Makah whalers of the Olympic Peninsula in what is now Washington State imitated the grey whale quarry before each hunt, diving down deep into the water and staying down as long as possible. Each time they surfaced, the hunter would spout a mouthful of water towards the center of the lake, trying to sound like a whale. The most determined were reported to surface with blood trickling from their ears.

[4] Recorded by Vinson Brown in Peoples of the Sea Wind (1977), and cited by Roman.

25 February 2009

A natural history of violence

The difficulties of imagining an intelligent mollusk are embodied in octopus websites, many of which alternate stories of octopus intelligence with recipes for cooking the animal.
-- writes Eugene Linden. And the point gets a laugh (although many people I know who have actually spent time with live cephalapods refuse to eat them).

It is equally true, but less of a chuckle, that compassion for animals does not necessarily make people less averse to violence against other humans or less ready to profit from it. In a profile of the weapons developer Jerry Baber, Evan Ratliff notes:
When Baber was ten years old, his father took him hunting with a .22 rifle. "My daddy made me shoot a little squirrel", he says. "That poor thing was sitting there, looking at me, and just fell over. I didn't hunt after that".
Baber found a lucrative niche making precision bomb springs at the height of the Vietnam War:
"Everything that came out of airplanes -- timing and detonators -- came from us", [Baber] recalls. "We built two hundred and eighty-five thousand bomb fuses a month, with four or five springs in each one.

According to the profile, Baber's main concern at present is to convince to the Pentagon to deploy his AA-12 mounted on robot platforms.

How long before we see this mother in a Hollywood movie? Move over Chewbacca and the MG42!

24 February 2009

A place for life

This blog has speculated on the Gamburtsevs as a place for future life. It is now reported that liquid water flows in their valleys. Perhaps this already allows strange microbes life to flourish.

P.S. Environment ministers huddle.

Beyond strange

A fuller explanation from MBARI. (Hat tip Deep Sea News)

Also in the news: it looks as if the elephant shark, which evolved about 450 million years ago, may be the oldest vertebrate to have "the colour vision system we know as humans".

21 February 2009

Deep time aeronauts

In The Cosmonaut of the Erotic Future, Aaron Schuster is concerned with the history of levitation. A chapter in The Book of Barely Imagined Beings digresses on pterosaurs -- animals as heavy as or heavier than man but that could actually live the human dream of unassisted flight. The last few years, even months, have been a golden age of discovery regarding pterosaurs. This news about their breathing system is just one recent example.

(See Research article, Hoaxful monsters, Tetrapod zoology)

Chocolate factory

Among those exhibiting is performance artist Eloise Fornieles, who...presented a challenging piece called Carrion which involves her walking naked through piles of second-hand clothes. Also in the room is the hanging carcass of a cow. Onlookers are encouraged to write letters of apology for consumption, which the artist then inserts into the cow.
from a report on Natural Wonders, an exhibition at the Red October Gallery in Moscow staged by a gallery owner Maria Baibakova, 23, the daughter of nickel oligarch Oleg Baibakov.

20 February 2009

Crypto clunckers

Following the discovery of a giant prehistoric snake, a 'real' one pops up in Borneo.

Future minds

Some day, perhaps, my biological colleagues will be using [computers] to simulate many processes including the chemical complexities within living cells, how combinations of genes encode the intricate chemistry of a cell, and the morphology of limbs and eyes. Perhaps they will be able to simulate the conditions that led to the first life, and even other forms of life that could, in principle, exist.
So wrote Martin Rees in a recent article [1].  But Rees, who is giving a talk on 23 February about the world in 2050, thinks that there is a long way to go before "real machine intelligence" is achieved. [2] I know of at least two grounds on which people question this. The first asks you to consider a continuum which extends far lower and higher than the upper and lower bounds of human intelligence, which for convenience are 'village idiot' and 'Einstein'. Machine intelligence (according to this argument) may at present be far below 'village idiot' and inferior, even, to an earthworm in important respects; but it is, or is soon likely to be, increasing fast and by the the time it approaches the lowest level of human intelligence it is likely to be traveling so fast that it will pass by both the lower and upper bands of human intelligence in a very short time. Further (the argument continues), we cannot say with confidence that this will not happen within a few decades. [3]

The second argument is that Rees is looking at the wrong thing. Very roughly speaking, the intelligence that is changing is that of extended mind or minds in which individual human brains are only a part. [4] New technologies are changing the nature of cognition and experience in profound and significant ways. The Minority Report-type technology of the kind shown below could be just a start.


[1] Mathematics: The only true universal language

[2] The example Rees gives in support of this assertion-- that a supercomputer may be able to beat grand master at chess but cannot recognise and manipulate the pieces on a chess board as well as a five year old human -- does not help build a strong case. See, for example, this from Conscious Entities.

[3] This is my very crude account of an argument outlined by Eliezer Yudkowsky at a conference on global catastrophic risks. The hope is for Gandhian AI. An intelligence without compassion could be like the psychopath mentioned by Daniel Goleman here. [Intelligence may be more than one thing in more than one dimension, or course.]

[4] See, e.g., A new kind of mind and Andy Clark's Supersizing the Mind, alluded to at Out of Mind.

Baby Southern Keeled Ocotopus. Photo credit John Lewis

19 February 2009

'Stilled catastrophe'

...is a phrase used by Kathleen Jamie in an essay about a visit to the Surgeon's Hall in Edinburgh, one of Europe's great cabinets of misshapen beings.

She finds solace in a "mawkish piece of Victoriana", Rab and his Friends:
Don't think [the student surgeons] heartless...they get over their professional horrors and into their proper work, and in them pity as emotion ending in itself, or at least in tears and a long drawn breath, lessens -- while pity as a motive is quickened and gains power and purpose. It is well for poor human nature that it is so.

photo: Cephalothoracopagus twins by James Mundie

18 February 2009

Bradán feasa

Salmon can distinguish a single drop from their own river among 8 million litres of seawater.
-- Nature's Great Events: The Great Salmon Run. Some Pacific salmon swim as much as 2,000 miles up river. They move against strong currents with little effort, much as a yacht tacks into the wind.

17 February 2009

Toast (2)

James Hansen writes:
The most threatening change, from my perspective, is extermination of species. Several times in Earth’s long history rapid global warming of several degrees occurred, apparently spurred by amplifying feedbacks. In each case more than half of plant and animal species went extinct. New species came into being over tens and hundreds of thousands of years. But these are time scales and generations that we cannot imagine. If we drive our fellow species to extinction we will leave a far more desolate planet for our descendants than the world that we inherited from our elders. We will leave a world haunted by the memories of what was.
Another unknown over the next few decades or centuries may be whether humans, or their successors, create or deliberately select for the evolution of new life forms, and if so what the consequences may be.

See also Toast, Ghosts and shadows and On the Origin (and Fate) of Species

P.S. Hansen's article appeared in The Observer here on 15 Feb.

Great marine biology videos

Not suprisingly, a top ten selection includes three of cephalapods, including the number one.

16 February 2009

A global stomach

Chiasmodon niger, or the black swallower -- a deep-sea fish that can extend its stomach to three times its size to swallow fish that are larger than itself -- is one of hundreds "bipolar" species spanning between the polar regions.

A BBC report has more detail. One possible explanation may be that:
the deep ocean at the poles falls as low as -1C (30F), but the deep ocean at the equator might not get above 4C (39F).

There is continuity in the ocean as a result of the major current systems...; a lot of these animals have egg and larvae stages that can get transferred in this water.

13 February 2009

I'm a fan

Deep Sea News celebrates the deepest known sea fan, 5,850 meters down.

P.S. I was lucky enough once to spend a few hours with Stephen Cairns, one of those who identified this sea fan. He had, among other things, recently completed research which pointed to a correlation between the diversity of modern deep sea corals and shallow tropical ones.


Ben Beck...once noted that if you give a screw-driver to a chimpanzee it will try to use the tool for everything except its intended purpose. Give one to a gorilla and it will rear back in horror -- "Oh my God, it's going to hurt me" -- then try to eat it, and ultimately forget about it. Give it to an orangutan, however, and the ape will first hide it and then, once you have gone, use it to dismantle the cage.
-- Eugene Linden

(Jason Hribal is angrier)

12 February 2009


I am sometimes asked what 'Anthropocene extinction', a tag used for The Book of Barely Imagined Beings, means. A good place to start is an account from the Stratigraphy Commission of the Geological Society of London, relayed in a stylish piece [1] by Mike Davis:
This new age [they explain] is defined both by the heating trend...and by the radical instability expected of future environments...They warn that "the combination of extinctions, global species migrations and the widespread replacement of natural vegetation with agricultural monocultures is producing a distinctive contemporary biostratigraphic signal. These effects are permanent, as future evolution will take place from surviving (and frequently anthropogenically relocated) stocks." Evolution itself, in other words, has been forced into a new trajectory.

[1] Who Will Build the Ark? The Utopian Imperative in an Age of Catastrophe, linked at Global Dashboard on 12 Feb. Another view (but one with which I do not necessarily wholly agree either) comes from Thomas Homer-Dixon in Our Panarchic Future.

See also Toast (2).

11 February 2009

10 February 2009


The BBC has stunning aerial footage of narwhals

Chimaera, the bestiary blog, posted on other living unicorns last month.

In 2007 Jangeisler in Greenland noted this bloody severed head of a, um, duonodon donoceros [1] spotted by one Aron Aqqaluk Kristiansen from Kangersuatsiaq:

On a lighter note:

Carl Huber at the Warehouse Comic

[1] Another photo here suggests this is not a fake.

9 February 2009

Not so super

Parallels between the ants and ourselves are striking for the light they shed on the nature of everyday human experiences. Some ants get forced into low-status jobs and are prevented from becoming upwardly mobile by other members of the colony. Garbage dump workers, for example, are confined to their humble and dangerous task of removing rubbish from the nest by other ants who respond aggressively to the odors that linger on the garbage workers' bodies.
-- Tim Flannery in a review article of The Superorganism by Bert Hölldobler and Edward O. Wilson.
All of a sudden, a pipe protruding into the drain above his head started spewing out water and human faeces that poured over his body.
-- Rupa Jha on 'My life cleaning Delhi's sewers'

Jumping brains and scary monsters

It's long been observed that, as Michael Brooks puts it [1],
human brains effortlessly conjure up an imaginary world of spirits, gods and monsters, and the more insecure we feel, the harder it is to resist the pull of this supernatural world.
And Brooks does a good job in summarizing and contrasting analysis from Scott Atran, Justin Barrett and others doing useful research into this phenomenon.

This post touches briefly on just one point: the theory mentioned by Paul Bloom at Yale that our brains have separate cognitive systems for dealing with living things on the one hand and inanimate objects on the other ("common-sense dualism"). It is argued, further, that strange things can happen when activity jumps between the two. I have made no proper study of this, but earlier today experienced the following.

Walking in the snow and slush through the local park, I half-noticed a dark blob smaller than a tennis ball on the path a few paces in front of me. Just as I was walking by I felt, as quickly as the involuntary reflex that withdraws a hand from a burning stove, a sudden shock of fear. In what seemed like the quarter or half second that followed, I attended to the object and saw it to be a stuffed cloth toy printed on the side with a picture of a blue tit or other small bird. It was a crude representation, obviously not alive and clearly harmless. [2] It had, however, been enough to spook me. [3]

My intuition is that as I approached the object (and I am aware that I had glanced at it few paces ahead) a system in my brain categorised it as inanimate, but that as I passed by the assessment changed: the object was registered as just possibly alive. The change was sudden and a sharp warning ran through my brain before closer inspection -- yup, it's just a dirty toy in the slush -- shut the warning down.

An evolutionary psychologist would say (I guess) that my ancestral 'wiring' was tripped for potential harm from, say, a snake or poison spider. There may be something to that. What struck me at the time, however, was a sense of flipping rapidly between two different mental states. Anyway, the experience seems to not contradict the idea that there are separate cognitive systems in the brain for living and non-living things.


[1] Born believers - how your brain creates god. See also A natural history of belief

[2] Unless, of course, Al Qaeda's Oxford franchise is planting IEDs inside wee cuddly animals toys.

[3] I think experiences like this are quite common.  P.S.: A friend writes with a simple explanation: "you are not getting enough sleep".

6 February 2009

Kids and kin

When Ahla comes home in the evening after feeding, she will go...through a door to the lambs' enclosure. From here, she can only hear the adult animals but not see them. Once she hears from inside the voice of a lamb that is calling for its mother, she will retrieve the correct lamb and jump through the opening...and put it underneath its mother so it can drink. She does this flawlessly even when several other mothers are calling and several lambs are responding at the same time... She also retrieves lambs and brings them back even before mother and infant have begun calling. Mrs Aston [the farm's owner] noted that "No local personnel and no white person would be able to assign correctly the 20 or more identically looking lambs to the mothers. However Ahla is never wrong".
Ahla, explain Dorothy Cheney and Robert Seyfarth [1], was a baboon. According to their source, she was never trained to recognise the kinship relations between mother goats and their kids:
She does things that she has never observed and that she has never been told. Ocassionaly though, she was punished with a belt when for instance she took a lamb up into the top of the trees where she slept.

[1] Baboon Metaphysics (2007). Cheny and Seyfarth record that goat herding with baboons was practiced by the Namaqua people before it was practiced by people of European descent in Southern Africa. Their source for the story of Ahla is Hoesch, von W. (1961) Uber Ziegen huetende Baerenpaviane. Other amazing baboon stories include Jack the Signalman.

Like mind

[It] is hard to say what is instinct in animals & what is reason, in precisely the same way [it] is not possible to say what [is] habitual in men and what reasonable. …as man has hereditary tendencies, therefore man's mind is not so different from that of brutes.
-- Charles Darwin (1838 a), quoted in Baboon Metaphysics (2007).
Interest in the idea of a herd mentality [in humans] has been renewed by work into mirror neurons - cells that fire when we perform an action or watch someone perform a similar action. It suggests that our brains are geared to mimic our peers. "We are set up for 'auto-copy'," says the psychologist Jonathan Haidt...[who] thinks this research helps explain why fascist leaders, amongst others, use organised marching and chanting to whip crowds into a frenzy of devotion to their cause, though these tactics can be used just as well for peace, he stresses.
-- from How to control a herd of humans.
This notion of the autonomous individual who is in charge of his or her fate is one that I couldn't really subscribe to.
-- W G Sebald quoted by Will Self.

Life on Mars

What do we do if we find life on Mars? It is possible that martian life is on the same tree of life as Earth life because of the exchange of meteorites between the two planets. Alternatively, it may be that life on Mars represents a second genesis--an independent origin of life. Contamination by even one Earth bacterium may be a serious issue of environmental ethics. Furthermore, if we find evidence of a second genesis, then this may open discussions of warming Mars to help that alien life to flourish. Scientists and policy-makers who consider this choice will have to deal with any contamination left on Mars by previous explorers, so that it does not flourish instead.
-- from Biologically Reversible Exploration by Christopher P. McKay.

(See also Should Mars be treated like a wildlife preserve?. Some Mars posts here)

5 February 2009

Hop, skip and a jump

Christopher MacLeod and colleagues at the Robert Gordon University in Aberdeen have taken the idea of evolutionary algorithm to "evolve" an optimal control system for a robot a step further, and developed an incremental evolutionary algorithm (IEA) capable of adding new parts to the robot brain over time:
The team started with a simple robot the size of a paperback book, with two rotatable pegs for legs that could be turned by motors through 180 degrees. They then gave the robot's six-neuron control system its primary command - to travel as far as possible in 1000 seconds. The software then set to work evolving the fastest form of locomotion to fulfil this task.

"It fell over mostly, in a puppyish kind of way," says MacLeod. "But then it started moving forward and not falling over straight away - and then it got better and better until it could eventually hop along the bench like a mudskipper."
-- Unnatural selection: Robots start to evolve

click here for larger image

'Older', and 'everywhere'

  • Traces of [multicellular] animal life have been found in rocks dating back 635 million years.
  • research claims there are at least 361 intelligent civilisations in our galaxy and possibly as many as 38,000. [1]
(See also Just wondering)


[1] 15 Feb: Galaxy has 'billions of Earths'.

4 February 2009


The eldest of the fishermen, Memo, rubs his grizzled chin in somber recollection, for one of our students has just asked a pointed and painful question: Which species have disappeared in his lifetime?

Solemnly, as though he’s reciting the names of his own deceased ancestors, Memo begins: the sea cucumbers, the fan clam, the lion’s paw scallop . . . . He’s working his way back in time, I think, moving from the most recently vanished toward the creatures that disappeared when he was a child.

In the early ’90s, he reaches the sharks; in the ’70s, the sea turtles; in the ’60s, the giant sea bass; and in the years of his childhood, the great totoaba, a six-foot croaker that was once pulled from these waters by the million.
-- Aaron E Hirsh, who argues that a system of “individual transferable quota”, or “fish shares”, is can offer a path to more sustainable fisheries in many places.

[1] See also Saenz-Arroyo, A, et al. 2005. Rapidly shifting environmental baselines among fishers of the Gulf of California. Proceedings of the Royal Society B. DOI: 10.1098/rspb.2005.3175.

Very like itself

Knowing (more or less) what happened next, Maiacetus looks 'transitionary'. But there is something to be said for trying to imagine it just for what it was: a 'complete' being.

Blog posts occasioned by New Protocetid Whale from the Middle Eocene of Pakistan include (in alphabetical order): Greg Laden, Laelaps, The Loom, New Scientist and Not Exactly Rocket Science. (The Wiki overview of cetacean evolution is also useful.)

P.S. New Scientist has a gallery here.

3 February 2009

On not crashing the planet

The discovery [that these jellyfish are spreading almost everywhere] underscores "our remarkable underestimation of the extent to which the ocean has been reorganized." 
-- says the marine biologist James Carlton in a report about "immortal" jellyfish swarming the world's oceans. [1]

Humans, it appears, may be learning ever more about ecosystems and our impacts upon them, but we often do so as a by-product of what looks (with hindsight) like blind stumbling. [2] An example may be the transportation of billions of gallons of sea water around the world as ballast, which Craig Venter calls: 
a giant ecological experiment we have been doing irrationally for decades and decades. [3]
It turns out that, absent human influences, 85% of the DNA sequence in oceanic bacteria, archaea and viruses is (was) unique every two hundred miles.  The consequences of mixing the seas up are not known.

Venter's assertion is reminiscent of Roger Revelle's momentous observation in 1957:
human beings are now carrying out a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future.
Inadvertent 'experiments' -- involving jellyfish, oceanic micro-organisms, the global climate and much else -- arise from a global economy driven by huge social forces on which ecosystem science has to date had only a tiny influence.

Redressing the 'clumsiness' of those forces would probably require huge changes in awareness, among other things. [4] Tools like Google oceans (and, one day, more sophisticated ones) may play a useful role, perhaps more than we presently imagine; but they will have limits. In a reflection from Andy Revkin, Stephen Kellert cautions:
The sad reality is that while more abstract, vicarious/representational awareness of nature and its conservation via the video and computer have grown enormously, concurrently, there has been a profound decline in more commonplace, everyday experience and contact with nature and the often deeper and more realistic and lasting appreciation and action that comes from this personal involvement.


[1] Here's another story on Tracking jellyfish blooms.

[2] (added 4 Feb) In a talk at the Zoology faculty at Oxford University relating to the paper Maximum Entropy and the State-Variable Approach to Macroecology, John Harte suggested that ecology is progressing beyond the gathering of data (the 'Brahe stage') and patterns (the 'Kepler stage' [sic]) towards general laws (the 'Newton stage').

[3] Genomics: from humans to the environment. A lecture at the James Martin 21st Century School. Roughly 34 minutes in to the podcast.

[4] It's not so much that we're riding a tiger, but that we are [part of] the tiger. This is expressed in a way I find compelling but disturbing and partly questionable ("command?") by Roberto Unger (Nature in its place, New writings):
...We are unquiet in nature because the mind concentrates and focuses a quality diffuse in nature: the mind is inexhaustible and therefore irreducible and uncontainable. No limited setting, of nature, society, or culture, can accommodate all we -- we the species, we as individuals -- can think, feel, and do. Our drivenness, including our drive to assert power over nature, follows from our inexhaustibility. We should not, and to a large extent we cannot, suppress, in the name of delight, stewardship, or reverence, the initiatives by which we strengthen our command over nature...

...Nothing should prevent us from tinkering with our natural constitution, inscribed in genetic code, to avoid disease and deformity. The place to stop is the point at which the present seeks to form human beings who will deliver a future drawn in its own image. Let the dead bury the dead is what the future must say back, through our voices, to the present. To let the future go free would show more than power. It would show wisdom.

2 February 2009

Seeing differently

Over at The Other 95% Eric Heupel has a very nice post describing a talk by Roger Hanlon on cephalopod camouflage behaviour.

Cephalopod skin colouration is one of the great wonders of nature. But when it comes to cool, nothing beats Vampyroteuthis.

1 February 2009

The Now

Once Einstein said that the problem of the Now worried him seriously. He explained that the experience of the Now means something special for man, something essentially different from the past and the future, but that this important difference does not and cannot occur within physics. That this experience cannot be grasped by science seemed to him a matter of painful but inevitable resignation. I remarked that all that occurs objectively can be described in physics; and, on the other hand, the peculiarities of mans’ experiences with respect to time, including his different attitude towards past, present and future, can be described and (in principle) explained in psychology.

But Einstein thought that these scientific descriptions cannot satisfy our human needs: that there is something essential about the Now which is just outside the realm of science.
-- Rudolf Carnap, quoted by Lee Smolin in On the reality of time and the evolution of laws (PIRSA:08100049)
Right now we are both alive. Better you and I not think too much about this fact, or we might be overwhelmed and paralyzed by joy.
-- Roberto Unger

[Image: a comb jelly, in vague allusion to the Meduso anthropic principle although, of course, comb jellies and jellyfish are not the same]


Noting gaps in Charles Darwin's knowledge, John Whitefield also highlights of some of ours today:
The debate now centres on whether the patterns seen in the rocks -- mass extinctions, sudden burst of diversification, the timing of the origin of particular groups --reliably reflect the history life, or whether they're artefacts of preservation and sampling. Does diversity, in general, seem to rise through time, for example, because we have more new rocks than old ones?

Molecular clocks -- using DNA differences to estimate divergence times -- have thrown another factor into the mix, because they tend to suggest that most groups originated long before they show up in the rocks.

They had to have arose a bit earlier, of course, but often molecular dates of origin are twice as old as fossil dates. Some molecular studies, for example, put the origin of the animals back to about one billion years ago, hundreds of millions of years before any fossils show up. Some have argued that the improbability of soft-bodied animals being fossilized explains why they don't show up in the rocks. Other think the molecular clocks are wrong.

image: from Knoll & Carroll