Absence can speak volumes. The lack of sediment in a flat piece of ground—a track—can testify to the footstep of a dinosaur that once walked on it. The lack of minerals in a solid shell—a hole—can reveal the presence of parasite that was once trapped in it. The world’s museums are full of such “trace fossils”, but so are many of the world’s art galleries.
The image above is taken from a woodcut currently residing in Amsterdam’s Rijksmuseum. It was made by etching a pattern into a block of wood, so that the remaining raised edges could be dipped in ink and used to print an image. These woodcuts were the main way of illustrating European books between the 15th and 19th centuries, and were used for at least 7 million different titles.
But as you can see, the print is littered with tiny white holes. These are called wormholes, and inaccurately so—they’re actually the work of beetles. The adults laid their eggs in crevices within the trunks of trees. The grubs slowly bored their way through the wood, eventually transformed into adults, and burrowed their way out of their shelters. The artists who transformed the tree trunks into printing blocks also inherited the exit-holes of the adult beetles, which left small circles of empty whiteness when pressed onto pages.
The beetles only emerged a year or so after the blocks were carved. The holes they left must have been frustrating, but remaking them would have been expensive. So the blocks were kept and reused despite their defects, unless the beetles had really gone to town. The holes they left behind preserve a record of wood-boring beetles, across four centuries of European literature. These holes are trace fossils. They’re evidence of beetle behaviour that’s been printed into old pages, just as dinosaur tracks were printed into the earth.
Now, Blair Hedges from Pennsylvania State University has used these fossils to study the history of the beetles that made them.
Last Friday, a group of volunteers gathered in the Royal Society in London to edit female scientists into the history books—or at least, into Wikipedia. Their goal was to start fixing the online encyclopaedia’s comparatively thin information about women in science and technology.
I attended the “edit-a-thon”, reporting for Nature. Before I turned up, I wondered about the rationale behind holding a specific event to edit Wikipedia, which can be done at any time and place. I also wondered how much the editors could accomplish in just 3.5 hours. Both concerns were addressed on the day, and in the piece. Take a look. Also, there was an Ada Lovelace/Wikipedia cake.
It relies on a radioactive version of carbon called carbon-14, which is formed in the atmosphere and is taken up by plants (and whatever eats the plants). Once these die, the carbon-14 in their bodies decays away at a steady, predictable rate. By measuring it, we can calculate how old an ancient sample is.
But there’s a catch. The levels of carbon-14 in the atmosphere vary from year to year, so scientists need some way of assessing these fluctuations to correct their estimates. They need long-running timetables, where each year in the past several millennia can be “read”, but where true levels of atmospheric carbon-14 can be measured.
And now, in the bottom of a Japanese lake, scientists have found the best such timetable yet. As I write in The Scientist:
The sediment of a Japanese lake has preserved a time capsule of radioactive carbon, dating back to 52,800 years ago. By providing a more precise record of this element in the atmosphere, the new data will make the process of carbon-dating more accurate, refining estimates by hundreds of years.
The data will allow archaeologists to better gauge the age of their samples and estimate the timing of important events such as the extinction of Neanderthals or the spread of modern humans through Europe.
“It’s like getting a higher-resolution telescope,” said Christopher Bronk Ramsey from the University of Oxford, who led the study. “We can look [with] more detail at things [such as] the exact relation between human activity and changes in climate.”
Image by Christopher Bronk Ramsey
On November 2nd, 2010, more than 61 million adults visited Facebook’s website, and every single one of them unwittingly took part in a massive experiment. It was a randomised controlled trial, of the sort used to conclusively test the worth of new medicines. But rather than drugs or vaccines, this trial looked at the effectiveness of political messages, and the influence of our friends, in swaying our actions. And unlike most medical trials, this one had a sample size in the millions.
It was the day of the US congressional elections. The vast majority of the users aged 18 and over (98 percent of them) saw a “social message” at the top of their News Feed, encouraging them to vote. It gave them a link to local polling places, and clickable button that said “I voted”. They could see how many people had clicked the button on a counter, and which of their friends had done so through a set of randomly selected profile pictures.
But the remaining 2 percent saw something different, thanks to a team of scientists, led by James Fowler from the University of California, San Diego. Half of them saw the same box, wording, button and counter, but without the pictures of their friends—this was the “informational message” group. The other half saw nothing—they were the “no message” group.
By comparing the three groups, Fowler’s team showed that the messages mobilised people to express their desire to vote by clicking the button, and the social ones even spurred some to vote. These effects rippled through the network, affecting not just friends, but friends of friends. By linking the accounts to actual voting records, Fowler estimated that tens of thousands of votes eventually cast during the election were generated by this single Facebook message.
One does not simply start mummifying one’s dead. Mummification is a technically challenging business that involves sophisticated tricks for preparing a corpse. It’s also steeped in intricate cultural traditions. How does such a practice start?
Chilean scientist Pablo Marquet has tried to answer that question by studying the world’s oldest mummies – those created by the Chinchorro people of northern Chile. The Chinchorro were preserving their dead some two thousand years before the Egyptians started doing so. Rather than just mummifying their elites, the Chinchorro preserved all of their dead – man and woman, elderly and infants. They went to great pains to do so. They would remove the organs and muscles of their dead, reinforce the skeletons with sticks, and fill the bodies with earth and vegetation to get the right shape. They covered the body in a mud coat and clay mask, and decorated it with colour.
Marquet thinks he knows why these practices began. Rather than simply looking at cultural factors, he has intimately tied the practice into changing climates and shifting population sizes. At the time that they started mummifying cadavers, the Chinchorro had gone through a population boom, driven by rich coastal seas. But they also lived in the Atacama Desert: the so-called driest place on Earth. In such an arid environment, any buried corpses would have taken their time to decay, if they did at all. The very land around them naturally mummified the corpses, and the Chinchorro simply followed suit.
We’ve all had that annoying feeling when we fail to find a word that’s just at the tip of our tongues. Usually, these moments are passing nuisances, but they are a more severe impediment for a British family known as JR. Eight of them suffer from an unusual problem with “semantic cognition” – the ability to bind words to their meanings during thought or communication.
They can’t remember words, names, or topics of conversation – all of us get this, but the JR family experiences a more extreme version. They make errors in everyday conversations when they use words with related meanings in the wrong places. Their comprehension falters to the extent that reading books or following films is hard work.
These difficulties have caused them much social anxiety, and hampered their ability to cope with school and work. But for scientists, they are undeniably exciting because they seem to stem from a single errant gene. If that’s the case, the gene apparently affects the intertwining of concepts and language, but not any other mental abilities – the affected family members are otherwise intelligent and articulate. The JR family could lead us to new insights about language, thought and memory, just as similar families have done in the past.
The tunes embedded above weren’t written by a composer, but fashioned through natural selection. They are the offspring of DarwinTunes, a program which creates bursts of noise that gradually evolve based on the preferences of thousands of human listeners. After hundreds of generations, tracks that are boring and grating soon morph into tunes that are really quite rhythmic and pleasant (even if they won’t be topping charts any time soon).
DarwinTunes is the brainchild of Robert MacCallum and Armand Leroi from Imperial College London. “We suspected that musical styles evolve through Darwinian natural selection,” says MacCallum. “They are copied and modified from artist to artist and generation to generation, with popular styles more likely to be copied as they get more exposure. “ The duo created DarwinTunes to see if music could actually evolve in this way.
The DarwinTunes tracks are all 8-second-long loops, each encoded by a ‘digital genome’ – a program that determines which notes are used, where they’re placed, the instruments, the tempo, and so on. The genomes of two parent loops can shuffle together in random ways to produce daughter loops, which also develop small random mutations. This mimics the way in which living things mate and mutate. It also mimics the way in which composers merge musical styles together, while inventing new motifs.
The experiment began with 100 randomly generated loops. On the DarwinTunes website, listeners could listen to these and rate them on a five-point scale, from “I can’t stand it” to “I love it”. Every time 20 loops were rated, the top 10 pair off, mate with each other to produce two daughters, and die. At any time, there are only 100 loops in the total population.
To date the loops have been evolving for 3,060 generations, and over 50,000 of them have been born. By taking loops from DarwinTunes’ entire history and asking volunteers to rate them, MacCallum and Leroi showed that they became more appealing with time. For example, they were more likely to contain chords found in Western music and they contained more complex rhythms. “We hoped for slightly more “advanced” music, but were very happy with the results,” says MacCallum.
This upward rise in appeal only lasted for 500 or 600 generations. After that, the loops hit a plateau and apparently stopped evolving. MacCallum and Leroi think that this is because the loops become so complex that their intertwining melodies and rhythms don’t merge very well. The act of mating, rather than combining the best of both parents, ends up splitting up elements that work well together.
Alternatively, it may be that as the loops become well adapted to the tastes of their listeners, it becomes harder to change them without messing something up – they become trapped in an adaptive peak, unable to reach a new peak without first crossing into a valley. Both of these processes have their counterparts in the world of real genetics. MacCallum and Leroi argue that this might explain why many old musical styles tend to be very conservative, changing little over thousands of years.
DarwinTunes is the latest in a line of digital evolution programs, where computer code copies itself, mutates, evolves and adapts. For example, in The Blind Watchmaker, Richard Dawkins describes a programme of the same name that can evolve complex shapes from initially simple collections of lines. These programs never fully reflect the reality of evolution, but they allow scientists to ask basic questions about evolution in a controlled way. They can set up controlled experiments, repeat them, replay evolution from specific points, and analyse how specifically their artificial creations have changed. It’s incredibly hard (but not impossible) to do that with actual living things.
But Michael Scott Cuthbert, who works on computer-aided musical analysis at MIT, is sceptical that the approach tells us anything about the evolution of music. “They have shown that people can sense a glimmer of the things they like about music even when most of it consists of sounds they hate,” he says. “But it doesn’t give any information about why music sounded differently in the past, why people like different things today, or how music might evolve in the future.”
“Suppose you randomly threw car parts into piles and asked people to rate those they’d most like to buy,” he says. “Then you took parts from the highest-rated heaps, and rearranged them into new heaps. People might hate all of them at first, but they’d probably rate the ones with four tires or a trunk in the back or a steering wheel in the drivers’ seat higher than the rest. Do that long enough and I wouldn’t be surprised that you’d eventually get something that looked like a 2011 Honda Civic. But that doesn’t mean that that’s how a car is made.”
MacCallum and Leroi acknowledge that real music changes in a more complex way than DarwinTunes currently captures. Composers write music with their own intentions, while listeners choose music based not just on what it sounds like, but on whether other people like it too. DarwinTunes could be changed to include these dynamics – volunteers could combine the loops themselves, and listeners could see earlier ratings.
“The big question for me is can we bring the quality up a level where you don’t have to be curious about the science to take part?” says MacCallum. “We can do that if we had millions of users, and segregated them based on musical genre preferences. It’s a chicken and egg problem though!”
Reference: MacCallum, Mauch, Burt & Leroi. 2012. Evolution of music by public choice. PNAS http://dx.doi.org/10.1073/pnas.1203182109
Image by Pedro Sanchez
More on music:
We are like dwarves standing on the shoulders of giants. This metaphor, famously used by Isaac Newton, describes how humans build on what has come before. Everything in our culture is the result of knowledge and skills that have slowly accumulated over time. Without this “cumulative culture”, we wouldn’t have our deep scientific knowledge, rich artistic traditions, or sophisticated technology. Simply put, you can’t make a car from scratch – first, you need to invent the wheel.
Are we alone in this respect? Certainly, many other animals can learn knowledge and skills from each other, and many of them have cultural traditions. But Newton’s metaphor involves not just the spread of knowledge, but its gradual improvement. We build on the past, rather than just passing it along. As generations tick by, our culture becomes more complex. Do other species show the same ‘cultural ratchet’?
Lewis Dean from the University of St Andrews tried to answer that question by presenting human children, chimpanzees and capuchin monkeys with the same task: a puzzle box with three, increasingly difficult stages, each one building on the last.
Antique Italian violins, such as those crafted by Antonio Stradivari or Giuseppe Guarneri “del Gesu”, can fetch millions of dollars. Many violinists truly believe that these instruments are better than newly made violins, and several scientists have tried to work out why. Some suspected at the unusually dense wood, harvested from Alpine spruces that grew during an Ice Age. Others pointed the finger at the varnish, or the chemicals that Stradivari used to treat the wood.
The duo asked professional violinists to play new violins, and old ones by Stradivari and Guarneri. They couldn’t tell the difference between the two groups. One of the new violins even emerged as the most commonly preferred instrument.
I originally wrote this feature about the amazing Erez Lieberman Aiden back in June. It’s been one of the most popular posts on Not Exactly Rocket Science over the past year, and it was recently nominated for inclusion in the latest edition of Open Lab, the anthology of the world’s best science blogging. For that reason, I’m giving it another airing.
Erez Lieberman Aiden is a talkative witty fellow, who will bend your ear on any number of intellectual topics. Just don’t ask him what he does. “This is actually the most difficult question that I run into on a regular basis,” he says. “I really don’t have anything for that.”
It is easy to understand why. Aiden is a scientist, yes, but while most of his peers stay within a specific field – say, neuroscience or genetics – Aiden crosses them with almost casual abandon. His research has taken him across molecular biology, linguistics, physics, engineering and mathematics. He was the man behind last year’s “culturomics” study, where he looked at the evolution of human culture through the lens of four per cent of all the books ever published. Before that, he solved the three-dimensional structure of the human genome, studied the mathematics of verbs, and invented an insole called the iShoe that can diagnose balance problems in elderly people. “I guess I just view myself as a scientist,” he says.
His approach stands in stark contrast to the standard scientific career: find an area of interest and become increasingly knowledgeable about it. Instead of branching out from a central speciality, Aiden is interested in ‘interdisciplinary’ problems that cross the boundaries of different disciplines. His approach is nomadic. He moves about, searching for ideas that will pique his curiosity, extend his horizons, and hopefully make a big impact. “I don’t view myself as a practitioner of a particular skill or method,” he tells me. “I’m constantly looking at what’s the most interesting problem that I could possibly work on. I really try to figure out what sort of scientist I need to be in order to solve the problem I’m interested in solving.”
It’s a philosophy that has paid dividends. At just 31 years of age, Aiden has a joint lab at MIT and Harvard. In 2010, he won the prestigious $30,000 MIT-Lemenson prize, awarded to people who show “exceptional innovation and a portfolio of inventiveness”. He has seven publications to his name, six of which appeared the world’s top two journals – Nature and Science. His friend and colleague Jean-Baptiste Michel says, “He’s truly one of a kind. I just wonder about what discipline he will get a Nobel Prize in!”