A couple of weeks ago I wrote a blog post about the Turkish discovery of a 4000-year-old scalpel made of obsidian, along with skulls that had clearly been operated on. Since then I've managed to track down the director of the excavation, Onder Bilgi, at his dig site in Ikiztepe near the Black Sea. He gave me some more information about the find and sent me some photos, so here's an update.

Bilgi told me that life in the early Bronze Age settlement of Ikiztepe was relatively sophisticated. The inhabitants lived in rectangular log houses with courtyards and ovens in front, and they were skilled in metallurgy. They mined copper in the local mountains, then alloyed it with arsenic to make weapons, tools, jewellery and religious symbols. During 37 years of excavations, Bilgi's team have found items such as loom-weights and spindle-whirls used in textile production, bone piercers, flintstone and stone tools, copper pins, small stone hand axes, and fragments of pottery bowls, jugs, jars, beakers, tea pots and pitchers.

The researchers have also gained an insight into the spiritual life of the villagers. For example, they found a huge copper alloy spearhead, 58 centimetres long, next to a circular clay platform with a hole in the centre. Bilgi thinks this may have been a ceremonial platform and that the spearhead was used in some kind of ritual performance. Other finds include a range of abstract religious symbols, such as plaques and pendants. The plaques are decorated with spirals, or bulls' horns, while the pendants are carved into crescent or disc shapes, probably representing the Moon and the Sun, or into female figures. "It is well-known that Anatolia was the homeland of mother goddess and bull cults," says Bilgi.

So what about the surgery? It turns out Bilgi's team has found two scalpels, which are each about four centimetres long and double-sided (see top photo). Each is still incredibly sharp: "they would still cut you today," says Bilgi. In a graveyard on a nearby hilltop, the researchers found 700 skulls, of which 14 appear to have been operated on. A very sharp tool (Bilgi reckons obsidian would have been the only material around at the time that was sharp enough) has been used to cut rectangular openings in the skulls. Bilgi says that the surgery appears to have been done for medical reasons such as relieving a build-up of blood during a brain haemorrhage, removing a tumour, and fixing up a head injury. The skulls show signs of healing, so the patients clearly survived, at least for a few years.

You can read more about all this in my interview, published in this week's New Scientist.

Back in March, I travelled to Los Angeles to participate in an event dedicated to the Antikythera mechanism, held at the beautiful Getty Villa (pictured). I spoke along with Jim Evans of the University of Puget Sound in Washington. He is an expert in the history of astronomy, and author of The History and Practice of Ancient Astronomy, which came in very useful when I was writing Decoding the Heavens.

It turned out to be a fun evening. We discussed the history of research on the mechanism, as well as the latest ideas on what it was, who might have made it and why. Evans also summarised some new research he and his colleagues had just published on the mechanism in the Journal for the History of Astronomy. Very briefly, the device has (among other things) a zodiac dial on the front, on which pointers moving at varying speeds were thought to show the varying movements of the sun, moon and five known planets through the sky. Evans' measurements of the 360 divisions on this dial show that they were unevenly spaced, in quite a deliberate way. He concludes that the movement of the sun was represented not with a pointer moving at varying speed as previously thought, but with a pointer moving at constant speed around an unequally divided dial. Although this might sound quite geeky, this finding was completely unexpected and has some fascinating implications, which I'll be writing about very soon.

Anyway, I'm telling you all this now because the lovely people at the Getty Villa have just posted a video of the March event, which was called Tracking the Cosmos: The Technology of the Antikythera Mechanism. You can watch it here.

When British-born physicist Derek de Solla Price decided to teach himself the history of science in the late 1940s, he didn't mess around. He acquired a full set of the Philosophical Transactions of the Royal Society (supposedly for the library of Raffles College, Singapore, where he had just taken up a teaching position) and used them as bedtime reading.

Starting with the first volume from 1665, he worked his way through the heavy journals, placing the finished volumes into neat, chronological piles on his bedside shelves. Then he noticed something strange. Though each stack covered the same number of decades, each pile was twice as tall as the one before - in effect forming an exponential graph against his bedroom wall.

Price raced to check modern journals in various fields of science and found that the same relationship held. By counting the number of papers published in journals, it was possible to describe mathematically the accumulation of scientific knowledge. Science was accelerating exponentially over time.

Thanks to this bedside observation, Price became fascinated by the measurement and progress of knowledge. He went on to pioneer research into the 2000-year-old Antikythera mechanism (see chapters 4 and 5 of my book, Decoding the Heavens). But he also founded an entire field of research - scientometrics, or the science of science itself. He is best known for his 1963 book, Little Science, Big Science, which explored the incredible expansion of science. There's also a list of his publications here.

Among other things, Price concluded that science had grown by five orders of magnitude (more than 16 doublings) since the formation of the Royal Society, meaning that "80 to 90 per cent of all the scientists who have ever lived are alive now".

He also showed that the pattern of recent citations among the world's scientific papers could reveal areas where research was actively progressing, not to mention the relative importance to science of particular journals, authors, institutions and even countries. And he declared the secret of distinguishing science from non-science: the higher the proportion of citations of newer papers (those less than five years old) compared to old ones (more than 20 years old), the more likely that the article is scientific.

Historians were a little sniffy about Price's quantitative approach, but scientists loved it. Price himself believed he was uncovering universal truths about the nature of knowledge and where it was taking humanity. Little green aliens coming to Earth would understand the Planck constant, the velocity of light, or the wave equation no matter how much they differ from us, Price mused. He felt that they would surely also recognise his scientometrics.

Price (pictured with his model of the Antikythera mechanism) died in 1983. But his scientometrics is still going strong. An article in the Independent yesterday (basically a rewrite of a column by Harvard postdoc and science writer Samuel Arbesman in the Boston Globe last month) describes how Arbesman has been using scientometric techniques to address the question of whether science is getting more difficult.

Arbesman analysed research into mammalian species, asteroids and chemical elements by plotting the average size of new discoveries over time. He assumed that the smaller species and asteroids are, the harder they are to find, and that for elements the reverse is true.

He found that in every case, the ease of discovery is going down over time, not just in a linear fashion, but exponentially. In other words (in these simplified examples at least) it is becoming exponentially more difficult to make new discoveries. "To find a slightly smaller mammal, or a slightly heavier chemical element, you can't just expend a bit more effort," says Arbesman. "Sometimes you have to expend orders of magnitude more."

This doesn't mean that science is slowing down, however. As Price originally pointed out, the number of scientists is increasing exponentially too. Funding levels have also been rising fast, especially for fields such as particle physics and medical research. And in some areas, exponential increases in computer processing power are also keeping the discovery rate high.

That last point is something that Price would have appreciated. Perhaps because of his work on the ancient Antikythera mechanism, he was fascinated by the potential of computers. Back in the early 1980s, when most modern computers were still slow grey boxes with the simplest of circuitry and just a few kilobytes of memory, he predicted that they would become the next technological driver of knowledge.

In fact, he reckoned that the world was entering a "computer age", in which networks of three-dimensional computer chips would allow machines to jump to conclusions and to think creatively, just like people. We'll have to wait and see whether than particular prediction comes true.

In the news today is the discovery of "Britain's oldest house". Found in Scarborough, North Yorkshire, it is estimated to have been built in 8500 BC.

But I prefer another story, which is getting much less attention, about the discovery of a 4000-year-old scalpel blade made of obsidian. Hürriyet News reported yesterday that it was found by archaeologists excavating a site called Ikiztepe Village in the Black Sea province of Samsun, in modern day Turkey.

In charge of the excavations is Istanbul University's Onder Bilgi. He says that the scalpel would have been used in ancient brain surgery.

Intriguing... Yesterday's Hürriyet article doesn't say why Bilgi believes the blade was a scalpel but a small amount of digging turns up an earlier report from the dig site, published on 28 July, which says that 8 out of 690 skulls discovered at a graveyard on a high hill near the village showed "traces of surgical operation".

Actually this isn't as far-fetched as it sounds. There are records of neurosurgery from Babylon and Egypt, using obsidian blades, from as far back as 3000 BC. And skulls bearing traces of centuries-old brain surgery have been found in Europe, Africa, Asia and North and South America. The earliest trepanned skulls date from the Neolithic stone age (see main picture, of a Neolithic girl's skull now held in the National History Museum in Lausanne, France; she survived the surgery).

In the 2005 book Textbooks of Operative Neurosurgery, in a chapter about drills in neurosurgery, Trimurti Nadkarni and Atul Goel write that there would have been three main techniques for getting through the skull - scraping, trepanning and cutting. In the earliest examples, a sharp-edged flint scraper or knife would have been used to make a circular or rectangular groove in the skull.

In ancient Peru, knives of bronze or obsidian were used. The wound was covered with a shell, a gourd, or even a piece of gold or silver. More recently, surgeons would have used a bow drill, made of springy wood with a leather thong wound around it.

So why obsidian? It's a naturally-occurring volcanic glass. It is formed when volcanic lava with a high content of silicon dioxide (silica) cools rapidly. The high silica content makes the lava very viscous, meaning that sizeable mineral crystals can't form before the magma cools. The absence of crystals in the glass means that when it breaks, the fracture surface is very smooth, with extremely sharp edges.

Obsidian was used for ancient projectile points and blades, including a very nasty Mesoamerican weapon called a macuahuitl, which was a 3 to 4-foot-long wooden club, with obsidian blades embedded in it (see pic). It was also polished to create early mirrors.

In fact obsidian blades are sharper even than surgical steel blades, so some modern surgeons advocate using obsidian scalpels today. A 1993 study on rats showed that cuts made with obsidian blades initially formed narrower scars, and healed quicker, than cuts made with surgical steel scalpels. Unfortunately such blades are not generally approved for use on humans, so it looks like we will be sticking with steel scalpels for a while yet.

Wow. I just got back from Sci Foo camp, a meeting of over three hundred people from all areas of science held at the infamous Googleplex in Mountain View, California. Whereas most science conferences tend to be focused around a particular topic, this was an unconference (inspired by similar events held in the technology industry), organised by Google, Nature and O'Reilly Media. There was no theme, no schedule, and no rules particularly except that we were encouraged to attend sessions that we knew nothing about, and talk to people we didn't know.

As well as scientists from all areas there were lawyers, journalists, bloggers, filmmakers and philosophers. History of science was also well represented, with attendees including Will Noel of the Archimedes Palimpsest project, Tilly Blyth, curator of computing at the Science Museum, Nigel Warburton, creator of the excellent Philosophy Bites podcast and Bonnie DeVarco, who for many years was chief archivist for the Buckminster Fuller archive, but is now involved in exploring visualisation technologies. There were also plenty of demos, including a lego model of the Antikythera mechanism made by Andrew Carol, which I'm hoping to write about in a future post.

The result was a fascinating weekend - I ended up in discussions about everything from how virtual reality technologies will affect children's brains, to the end of gravity as we know it. I blogged the event for New Scientist, so rather than repeat myself, here are links to all my posts from the meeting:

Lego to loo seats: an unconference at Google HQ

Are you ready for life in world 3?

Evolution of music and a dancing cockatoo

Rewriting gravity over a tuna roll

And here are some other attendees' posts that I enjoyed:

Letter from SciFoo: The joys and sorrows of the unconference (Carl Zimmer)

Correspondent's diary: Around the campfire (The Economist)

Sci Foo 2010 Un-conference at Googleplex (Nigel Warburton)

Even more links are collected here.