A brief moment in the magnificent history of mankind

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Isn’t that beautiful? It’s an ancient footprint in some lumpy rocks in Kenya…but it is 1½ million years old. It comes from the Koobi Fora formation, familiar to anyone who follows human evolution, and is probably from Homo ergaster. There aren’t a lot of them; one series of three hominin trails containing 2-7 prints, and a stratigraphically separate section with one trail of 2 prints and an isolated single print. But there they are, a preserved record of a trivial event — a few of our remote relatives taking a walk across a mudflat by a river — rendered awesome by their rarity and the magnitude of the time separating us.

Here’s one of the trails:

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Tessellated swath of optical laser scans of the main footprint trail on the upper footprint surface at FwJj14E. Color is rendered with 5-mm isopleths.

It’s an interesting bridge across time. There they were, a couple of pre-humans out for a stroll, perhaps on their way to find something for lunch, or strolling off to urinate, probably nothing dramatic, and these few footprints were left in drying mud to be found over a million years later, when they would be scanned with a laser, digitized, and analyzed with sophisticated software, and then uploaded to a digital network where everyone in the world can take a look at them. Something so ephemeral can be translated across incomprehensible ages…I don’t know about you, but I’m wondering about the possible future fate of the debris of my life that has ended up in landfills, or the other small smudges across the landscape that I’ve left behind me.

And what have we learned? The analysis has looked at the shape of the foot, the angle of the big toe, the distribution of weight as the hominins walked across the substrate, all the anatomical and physiological details that can be possibly extracted from a few footprints.

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Optical laser scan images color-rendered with 5-mm isopleths for footprints at both FwJj14E and GaJi10. (A) Isolated left foot (FUI1) on the upper footprint surface at FwJj14E. (B) Photograph of FUI8 on the upper footprint surface at FwJj14E, showing good definition of the toe pads; the second toe is partially obscured by the third toe. (C) Second trail on the upper footprint surface at FwJj14E, showing two left feet. (D) Third trail on the upper footprint surface at FwJj14E, showing a right and a left foot. (E) Print R3 from GaJi10 (22), re-excavated and scanned as part of this investigation. (F) Partial print (FUT1-2) on the upper footprint surface at FwJj14E; the heel area has been removed by a later bovid print. (G) Print FLI1 on the lower footprint surface at FwJj14E, rendered with 5-mm alternating black and white isopleths. (H) Inverted image of the toe area of print FUT1-1 with alternating 5-mm black and white isopleths. Note the locations of the pads of the small toes and the presence of a well-defined ball beneath the hallucial metatarsophalangeal joint. The first, third, and fifth toes are marked D1, D3, and D5, respectively.

The answer is that these beings walked just like us. The tracks are noticeably different from the even older footprints of australopithecines found at Laetoli, from 3.5 million years ago. The foot shape and the stride of Homo ergaster was statistically indistinguishable from those of modern humans, even though we know from the bones associated with these species that they were cranially distinct from us. This is not a surprise; it’s been known for a long time that we evolved these bipedal forms long ago, and that the cerebral innovations we regard as so characteristic of humanity are a relative late-comer in our history.

Remember, though, these are 1½ million years old, 250 times older than the age of the earth, according to creationists. That’s a lot of wonder and history and evidence to throw away, but they do it anyway.

Bennet MR, Harris JWK, Richmond BG, Braun DR, Mbua E, Kiura P, Olago D, Kibunjia M, Omuombo C, Behrensmeyer AK, Huddart D, Gonzalez S (2009) Early Hominin Foot Morphology Based on 1.5-Million-Year-Old Footprints from Ileret, Kenya. Science 323(5918):1197-1201.

Exposing the intimate details of the sex lives of placoderms

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The media is getting another science story wrong. I keep seeing this discovery of an array of fossil placoderms as revealing the origins of sex, and that’s not right. Sex is much, much older, and arose in single-celled organisms. Come on, plants reproduce sexually. A fish is so far removed from the time of origin of sexual reproduction that it can’t tell us much about its origins.

Let’s get it right. These fossils tells us about the origin of fu…uh, errm, mating in vertebrates.

What we have are a set of placoderm fossils from the Devonian (380 million years ago) of Western Australia (The Aussies are going to be insufferable, now that they can claim to be living in the birthplace of shagging) that show two interesting features: some contain small bits of placoderm armor that show no signs of digestion, and so are not likely to be relics of ancient cannibal feasts, but are the remains of viviparous broods — they were preggers. The other suggestive observation is that the pelvic girdle has structures resembling the claspers of modern sharks, an intromittent organ or penis used for internal fertilization.

[Read more…]

There is no one simple evolution story

I’ve never liked this stereotypical portrayal of evolution.

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It implies that evolution is linear, that it is going somewhere, and of course, that it is all about people — all the wrong messages. Yet it is ubiquitous, and probably the most common rendering you’ll find anywhere. Try googling for images of evolution, and you will turn it up, or variants on it, or jokes built on it…it’s a bit annoying and trite.

(Although, when I googled to find that image — which was easy — I also found this one.

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Very nice. I like it.)

This is actually a problem. When we’re trying to get the message of the science of evolution across to people, one thing that helps is having a story — people respond well to narratives. The canonical image definitely tells a story, which is probably why it caught the public imagination so well, but the problem is that it is the wrong story.

Evolution should not be portrayed as an epic tale with a beginning and an end, with a narrative drive to a conclusion, with a single hero or even any heroes at all. Trying to shoehorn it into a simple linear story destroys the meaning. Does this mean our efforts to catch the attention of a fickle public are doomed, because science does not fit the story-telling conventions that best fit the human mind?

Not necessarily. Here’s an interesting analogy, a comparison of the evolution story to a dramatic convention that the public does eat up happily: evolution is like a soap opera. I can see it.

Both have lots of characters and story lines, every one full of anguish and drama, some ending happily (for a while), others ending miserably; individuals come and go, they get their brief period in the spotlight, then poof, everything moves on to the next big new event. There is no one grand goal for the ensemble, just a series of overlapping dramas, some ridiculous, some mundane, and the vehicle to tie them all together is usually something commonplace — a town or a hospital, for instance — and stories can abandon that unifying premise freely. And it never ends!

Days of our Lives has been on the air since 1965. Dozens, probably hundreds, of characters have come and gone. There have been murders, affairs, rapes, and (for all I know) alien abductions. The show isn’t going anywhere. And yet as any soap-opera fan will tell you, their favorite soap has had dozens and dozens of riveting, heart-breaking stories over the years, that make the series so gratifying and rewarding in the long run.

And that’s exactly the deal with evolution. It isn’t going anywhere, and yet it’s going to keep on going and going and going for as long as there’s planet to go on, and even after that it’ll probably be going on someplace else.

Cool. And yet, somehow, all that chaos and confusion and complexity and strangely unresolvable big picture manages to engross viewers day after day after day, in the case of the soaps. There’s a lesson there that we need to figure out: how can we map the science of evolution onto the imaginations of human beings?

Francis Collins will be so disappointed

Collins has argued that one piece of evidence for god is the human moral sense, which he claims could not have evolved. I guess we’re going to have to call monkeys our brothers and sisters then, since researchers have found that monkeys have a sense of morality. (Let me guess; he’ll just push the magic moment of ensoulment back another 30 million years.) Furthermore, they have explanations for how altruism could have evolved.

Some researchers believe we could owe our consciences to climate change and, in particular, to a period of intense global warming between 50,000 and 800,000 years ago. The proto-humans living in the forests had to adapt to living on hostile open plains, where they would have been easy prey for formidable predators such as big cats.

This would have forced them to devise rules for hunting in groups and sharing food.

Christopher Boehm, director of the Jane Goodall Research Center, part of the University of Southern California’s anthropology department, believes such humans devised codes to stop bigger, stronger males hogging all the food.

“To ensure fair meat distribution, hunting bands had to gang up physically against alpha males,” he said. This theory has been borne out by studies of contemporary hunter-gatherer tribes.

In research released at the AAAS he argued that under such a system those who broke the rules would have been killed, their “amoral” genes lost to posterity. By contrast, those who abided by the rules would have had many more children.

It’s a little glib and speculative, but it’s enough to shut down the claim that morality couldn’t have evolved.

I also have deep reservations about some of the claims in the article.

Other studies have confirmed that the strength of a person’s conscience depends partly on their genes. Several researchers have shown, for example, that the children of habitual criminals will often become criminals too – even when they have had no contact with their biological parents.

Ugh. Criminality is too flexible and too easily influenced by the environment — strip me of my income and throw me on the streets, and I’ll become a criminal, too, if it keeps me and my family from going hungry. But then, I suppose anyone could claim those are just the genes of my roots in the lower socioeconomic classes.

Neandertal genome? Or a premature announcement?

In a potentially exciting development, researchers have announced the completion of a rough draft of the Neandertal genome in a talk at the AAAS, and in a press conference, and the latest issue of Science has a number of news articles on the subject. And that is a reason for having some reservations. There is no paper yet, and science by press release raises my hackles, and has done so ever since the cold fusion debacle. Not that I think this is a hoax or error by any means, but it’s not a good way to present a scientific observation.

Also, the work has some major limitations right now. They’ve got about 60% of the genome so far, and it’s all entirely from one specimen. From the age of these bones, degradation is inevitable, so there are almost certainly corrupted sequences in there — more coverage would give me much more confidence.

With those caveats, though, there are some tantalizing hints, and the subject is so exciting that it’s understandable why there’d be rush to announce. So far, they’ve identified approximately 1000-2000 amino acid differences in the coding part of the genome (human-chimp differences are about 50,000 amino acids), but there’s no report of any detectable regulatory differences.

I’m withholding judgement until I see a real paper; for now, you have to settle for a podcast with a science journalist, which just isn’t meaty enough yet.

You are not optimal

Gary Marcus, author of Kluge(amzn/b&n/abe/pwll) (a book I recommend), has an opinion piece in the Wall Street Journal that makes an important point: evolution does not produce rational, perfect, finely-tuned beings. It makes organisms that are good enough. Keep this in mind when looking at anything biological (like, say, an appendix), and it’s also true in economics, as Marcus points out — assuming that human beings will tend to make rational choices will lead to being fooled much of the time.

You are a very short note near the end of the symphony of life

Seed has compiled a short list celebratory articles and media for your Darwin Day — take a look. I rather liked The Evolution of Life in 60 Seconds: it’s very short, but it puts everything in perspective by listing key events in the 4.6 billion year history of the planet with appropriate timing to fit into one minute. If they’d put it into the context of the over 13 billion year history of the universe, it might have been even more dramatic.


Produced by Claire L. Evans.

Happy Darwin Day!

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Get out and celebrate the 200th anniversary of the birth of one of the most important scientists of all time, Charles Darwin, and the 150th anniversary of the publication of one of the most important books in biology, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. It’s that day!

I’m in Minnesota, and you have a couple of options here. The Bell Museum in Minneapolis is having a party!

Darwin Day Party
Thursday, February 12, 2009, 7 to 9 p.m.
Bell Museum Auditorium
$10/ free to museum members and University students

The speakers will present in the auditorium from 7 to 8 pm. Birthday cake and refreshments are served after the presentations.

Celebrate the 200th anniversary of Charles Darwin’s birthday! Part of a world wide celebration, the Twin Cities’ version is at The Bell Museum of Natural History this Thursday night. Join in the fun with cake, drinks and presentations by U of M scientists and educators. They will present funny, outrageous and controversial rapid-fire, media-rich presentations about Darwin and evolution. From the big bang to the human genome, hear the newest research and controversy on evolution and Darwin.

I’m rather far from Minneapolis, unfortunately — if you live in the west central part of the state, or the eastern part of the Dakotas, we’re having an open lecture here at the University of Minnesota Morris. Nic McPhee of the computer science discipline and PZ Myers of biology will be talking about “Paths to Complexity: How Biology and Computation can Build Intricate Processes and Systems” — it’s a kind of anti-intelligent-design talk that focuses on the amazing stuff we do know about how chance and selection can build complex systems and efficient solutions.

We’ll be on the UMM campus in HFA 6, at 5pm this evening. No charge, but come early — we expect to fill the joint up. If you can’t make it, it is going to be recorded and a podcast made available later.

Schinderhannes bartelsi

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Fans of the great Cambrian predator, Anomalocaris, will be pleased to hear that a cousin lived at least until the Devonian, over 100 million years later. That makes this a fairly successful clade of great-appendage arthropods — a group characterized by a pair of very large and often spiky manipulatory/feeding arms located in front of the mouth. Here’s the new fellow, Schinderhannes bartelsi:

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Holotype of Schinderhannes bartelsi. (A) Ventral. (B) Interpretative drawing of ventral side. l, left; r, right; A1, great appendage; A2, flaplike appendage; sp, spine; fm, flap margin; te, tergite; ta, trunk appendage. (C) Partly exposed dorsal side, horizontally mirrored. (D) Interpretative drawing of dorsal side. (E) Interpretative drawing of great appendages, combining information from the dorsal and ventral sides. (F) Radiograph. (G) Reconstruction. Scale bar, 10 mm [for (A) to (G)]. (H) Mouth-part. Scale bar, 5 mm.

There are some significant differences between familiar old Anomalocaris and Schinderhannes. Anomalocaris was a monster that grew to about a meter long; this little guy is about a tenth of that, around 4 inches. He also has those interesting “wings” behind his head, which presumably aided in swimming.

Another significant feature of this animal is that it has characters that place it in the Euarthropoda, which makes great appendages paraphyletic and primitively present in euarthropods. Those great appendages have long been a curiousity, and we’ve wondered whether they are a unique innovation that was completely lost in modern arthropods, or whether they evolved into one of the other more familiar cephalic appendages; the authors suggest that this linkage with the euarthropod family tree implies that chelicera (what you may recognize as the big paired ‘fangs’ of spiders) are modified great appendages.

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Cladogram; tree length, 87. Consistency index, 0.5402; retention index, 0.6552. (1) Peytoia-like mouth sclerites, terminal mouth position, lateral lobes, loss of lobopod limbs, and stalked eyes. (2) Great appendages. (3) Sclerotized tergites, head shield, loss of lateral lobes, and biramous trunk appendages. (4) Stalked eyes in front and loss of radial mouth. (5) Post-antennal head appendages biramous and antenna in first head position. (6) Free cephalic carapace, carapace bivalved, and two pairs of antennae. (7) Maxilla I and II. (8) Exopods simple oval flap. (9) Two pre-oral appendages and a multisegmented trunk endopod. (10) Post-antennal head appendages biramous and tail appendages fringed with setae. (11) Long flagellae on great appendage and exopods fringed with filaments. (12) Trunk appendages uniramous and eyes not stalked. (13) No posterior tergites. (14) Tail spines and chelicere/chelifore on first head position. (15) Proboscis. (16) Six post-antennal head appendages.

Kühl G, Briggs DEG, Rust J (2009) A Great-Appendage Arthropod with a Radial Mouth from the Lower Devonian Hunsrück Slate, Germany. Science 323(5915):771-773.