The origin of the evolutionary game – the ability of animals (including humans) and plants to reproduce sexually, genetically recombine to repair DNA, and then produce eggs, sperm or pollen – is an unresolved mystery in biology.

In an article published in the July/August issue of BioScience, University of Arizona researchers Harris Bernstein and Carol Bernstein provide insights into the early evolution of sexual organisms and the role environmental stressors had on sexual reproduction as a key survival strategy.

The UA department of cell biology and anatomy researchers argue that eukaryotes, or cells with a nucleus, adapted their meiotic ability to recombine chromosomes sexually into new genetically distinct entities from their ancestors, called prokaryotic cells.

The ability to recombine chromosomes through meiosis gives rise to eggs and sperm in humans. According to the Bernsteins’ theory, meiosis evolved to promote DNA repair, thereby greatly reducing DNA damage in resulting eggs and sperm.

After the repair during meiosis, when an egg meets a sperm, the chance of having a viable fetus is much improved, and the chance that the baby will have a newly arisen genetic defect is reduced.

Prokaryotic cells evolved to develop the ability to repair DNA through a process called transformation, which also promotes chromosome repair through a process called recombination.

In prokaryotic cells (which include bacteria), asexual reproduction is completed through a process called binary fission. In binary fission, each strand of the original double-stranded DNA molecule serves as template for the reproduction of a complementary strand as the cell readies to split into two parts.

Under certain conditions, these cells are capable of the exchange and repair of DNA through a process called transformation. Transformation is the transfer of a fragment of DNA from a donor cell to a recipient cell, followed by recombination in the recipient chromosome. The researchers call this bacterial process an early version of sex.

For eukaryotes, which include higher animals and plants as well as single-celled species such as yeast, reproduction occurs in two ways, through mitosis or meiosis.

In mitosis, one cell divides to produce two genetically identical cells. In cells committed to mitosis, if there is DNA damage, a good deal of the damage can be repaired, especially the damage on one strand of the DNA, where information on the opposite strand can direct the repair on the damaged strand of the double helical DNA.

Meiosis is required in sexual reproduction in eukaryotes. During meiosis, a cell with two copies of each chromosome, one from each parent, undergoes the process of recombination. This allows a special type of repair, not available during ordinary mitosis.
During meiotic recombination, the pairs of chromosomes line up next to each other, and if there is damage on either chromosome, repair can take place by recombination with the other chromosome. Meiotic recombination allows for the repair of damaged DNA as the chromosomes from each parent are broken and joined, resulting in different combinations of genes in each chromosome.

The prevailing theory is that eukaryotes developed the ability for meiosis and sexual reproduction from their ability to reproduce through mitosis and not from their early ancestor’s ability to reproduce through transformation.

“Our proposal, that the sexual process of meiosis in eukaryotes arose from the sexual process of transformation in their bacterial ancestors, is a new and fundamentally different perspective that will likely generate controversy,” the researchers predict.
Harris Bernstein is a professor of cell biology and anatomy. Carol Bernstein is an associate research professor of cell biology and anatomy.

“If it is assumed that meiosis arose only after mitosis was established, there would have been an extended period (while mitosis was evolving) when there was no meiosis, and therefore no sex, in eukaryotes. This assumption appears to be contradicted by evidence that the basic machinery for meiosis was present very early in eukaryote evolution,” the authors state.

A key argument in their hypothesis is that in both prokaryotes and simple eukaryotes, sexual cycles are induced by stressful conditions. Thus, the recombinational repair promoted by transformation and meiosis is part of a survival strategy in response to stress.

“Coping with DNA damage appears to be a fundamental problem for all life. For instance, the average human cell incurs about 10,000 DNA damages per day, of which 50 are double-strand breaks. The DNA damages are mostly due to the reactive oxygen species generated when converting food into energy. Thus, efficient DNA recombinational repair is an adaptation for cell survival and for producing new offspring, in higher organisms, through meiosis,” the researchers contend.

In bacteria – the most common prokaryote – transformation is typically induced by high cell density, nutritional limitation, or DNA-damaging conditions. In yeast, a eukaryote or protist, the meiotic sexual cycle is induced when the supply of nutrients becomes limiting or when the cells are exposed to oxidative stress and DNA damage, the team added.

“Observations suggest that facultative sex in bacteria and protists is often an adaptive response to stressful environmental conditions, as would be expected if transformation and meiosis were related adaptations,” the researchers write.

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A team of astronomers from Germany, Bulgaria and Poland have used a completely new technique to find an exotic extrasolar planet. The same approach is sensitive enough to find planets as small as the Earth in orbit around other stars.

The group, led by Dr Gracjan Maciejewski of Jena University in Germany, used Transit Timing Variation to detect a planet with 15 times the mass of the Earth in the system WASP-3, 700 light years from the Sun in the constellation of Lyra. They publish their work in the journal Monthly Notices of the Royal Astronomical Society.

Transit Timing Variation (TTV) was suggested as a new technique for discovering planets a few years ago. Transits take place where a planet moves in front of the star it orbits, temporarily blocking some of the light from the star. So far this method has been used to detect a number of planets and is being deployed by the Kepler and Corot space missions in its search for planets similar to the Earth.

If a (typically large) planet is found, then the gravity of additional smaller planets will tug on the larger object, causing deviations in the regular cycle of transits. The TTV technique compares the deviations with predictions made by extensive computer-based calculations, allowing astronomers to deduce the makeup of the planetary system.

For this search, the team used the 90-cm telescopes of the University Observatory Jena and the 60-cm telescope of the Rohzen National Astronomical Observatory in Bulgaria to study transits of WASP-3b, a large planet with 630 times the mass of the Earth.

“We detected periodic variations in the transit timing of WASP-3b. These variations can be explained by an additional planet in the system, with a mass of 15 Earth-mass (i.e. one Uranus mass) and a period of 3.75 days”, said Dr Maciejewski.

“In line with international rules, we called this new planet WASP-3c”. This newly discovered planet is among the least massive planets known to date and also the least massive planet known orbiting a star which is more massive than our Sun.

This is the first time that a new extra-solar planet has been discovered using this method. The new TTV approach is an indirect detection technique, like the previously successful transit method.

The discovery of the second, 15 Earth-mass planet makes the WASP-3 system very intriguing. The new planet appears to be trapped in an external orbit, twice as long as the orbit of the more massive planet. Such a configuration is probably a result of the early evolution of the system.

The TTV method is very attractive, because it is particularly sensitive to small perturbing planets, even down to the mass of the Earth. For example, an Earth-mass planet will pull on a typical gas giant planet orbiting close to its star and cause deviations in the timing of the larger objects’ transits of up to 1 minute.

This is a big enough effect to be detected with relatively small 1-m diameter telescopes and discoveries can be followed up with larger instruments. The team are now using the 10-m Hobby-Eberly Telescope in Texas to study WASP-3c in more detail.

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Astronomers have shed light on the mysterious origins of the fastest spinning stars known to science – millisecond pulsars.

Pulsars are dense, highly magnetised dead stars that emit radio waves along their magnetic poles.

These waves sweep around as the star rotates, a bit like lighthouse beams.

Writing in the journal Science, a team has worked out how millisecond pulsars might evolve from a type of binary star system which spews out X-rays.

The results show how old pulsars may start gathering matter from a companion star, emitting first X-rays and then radio pulses.

Observations taken over nine years, from 1998 to 2007, showed a pulsar collecting this mass in a disc, at the same time increasing its rotational speed.

The result uncovers a hitherto unseen step in the evolution of millisecond pulsars.

After collapsing into a neutron star following a supernova, pulsars tend to rotate quickly – every few hundredths of a second or so. But they often slow down with age, taking up to seconds for each rotation and eventually stopping altogether.

No-one put it together that it was going from an X-ray source into a radio millisecond pulsar until we found these radio pulsations Scott Ransom, National Radio Astronomy Observatory

However, a small population of neutron stars has extremely fast rotation – every few thousandths of a second. These millisecond pulsars are the fastest-rotating stars we know of.

One well-known class of system that is bright in the X-ray part of the electromagnetic spectrum but emits no radio waves is known as a low-mass X-ray binary or LMXB.

These systems typically consist of a neutron star with a lighter “normal” star nearby. Astronomers had long hypothesised that LMXBs might be millisecond pulsars in the making.

The idea is that the neutron star steals gas – which blocks radio waves – from its neighbour.

The gas first swirls around the neutron star like water around a plughole, forming an “accretion disc” surrounding it. The momentum the gas carries as it comes to rest on the neutron star increases its rotation speed.

The theory proposes that once the gas runs out, the disc disappears and the pulsar sprays out its radio pulses at higher speeds.

Over the last decade, astronomers have discovered LMXBs that show an accretion disc stage, resulting in a rotating system that spits out X-ray pulses.

But no one had seen these systems emitting the radio wave pulses that characterise millisecond pulsars.

Blink of an eye

In a wide-field survey using the Green Bank Telescope in West Virginia, US, in 2007, the team spotted a millisecond pulsar 4,000 light-years away.

Looking back through prior observations, they found the same object had previously been imaged by the Very Large Array telescope and the Sloan Digital Sky Survey. However, these observations suggested a very different scenario.

In 2000, the object seemed to possess an accretion disc of matter pulled from its companion star.

By 2002, the disc had disappeared again. Then, the 2007 measurements showed it was a millisecond pulsar, spinning around every 1.7 thousandths of a second.

A tiny neutron star gathers matter from a companion, spinning ever faster

“It appears this thing has flipped from looking like an LMXB to looking like a pulsar, as it experienced an episode during which material pulled from the companion star formed an accretion disk around the neutron star,” said co-author Scott Ransom of the National Radio Astronomy Observatory (NRAO).

“Later, that mass transfer stopped, the disc disappeared, and the pulsar emerged.”

He told BBC News: “The system that we found was identified as a weird system based on older optical and X-ray observations.”

“But no one put it together that it was going from an X-ray source into a radio millisecond pulsar until we found these radio pulsations.”

Those radio pulses vary in intensity and can disappear altogether, Dr Ransom said.

The team assumes that, towards the end of the mass transfer, the companion star gave up the last of its mass in fits and starts, so that there was probably a patchy mess of gas surrounding the pulsar that interfered with its regular radio pulses as observed on Earth.

Dr Ransom said the team was exceptionally lucky to have caught the system in the midst of its transition from X-ray emitter to millisecond pulsar – through observations taken over the cosmic equivalent of the blink of an eye.

The researchers say the results provide convincing evidence that the millisecond pulsar formation theory is correct, and Dr Ransom says it has inspired a return to studying known LMXB systems to see if they are intermittently firing out radio pulses.

“So far we’ve been completely unsuccessful. But, who knows, next year one or more of those systems may stop donating gas completely and a radio pulsar pops on.”

Timothy Peake, a 37-year-old test pilot in the Army Air Corps, has been accepted into the European Space Agency’s (Esa) Astronaut Corps.

The spaceman, who hails from Chichester, was unveiled at a ceremony in Paris, along with five other new colleagues from across Europe.

The other recruits to emerge from Esa’s latest trawl for new candidates include a woman astronaut.

There are two Italians, a Frenchman, a German, and a Dane.

But it is the UK citizen who is sure to command a lion’s share of the headlines.

Successive British governments have considered human spaceflight an expensive distraction, preferring to fund robotic exploration instead.

This policy has made it extremely difficult for British-born individuals to get into orbit.

“I hope it will now encourage the British government to contribute,” said Jean-Jacques Dordain, director-general of Esa. “With such a good guy [in Timothy Peake], how can they not contribute?”

Major Peake currently lives in Salisbury, Wiltshire. He is a helicopter test pilot and has a degree in flight dynamics.

He has been in the armed forces for 18 years. He flies primarily Apache helicopters and has over 3,000 hours to his credit.

New recruits

The 37-year-old Briton thanked his friends and family for their support during the selection process. He said: “It has been quite a difficult year and the waiting has been quite difficult during the past few weeks.

“If it wasn’t for the British Army, I wouldn’t be in this position, so I’m very grateful for the training and support I’ve received from them also.”

The first Briton in space was Sheffield-born chemist Helen Sharman. She had to secure private funding to fly to the Mir space station on a Russian Soyuz craft in 1991.

Three British-born astronauts have flown into space under an American flag: Michael Foale, Piers Sellers and Nicholas Patrick.

From 8,000 to six: Esa announced its new astronauts in Paris

The most recent non-governmental British-born astronaut was Richard Garriott. The wealthy games developer paid for his trip, again through the Russians.

But the European Space agency says its new astronauts were judged solely on their ability to do the job, not on national government policy.

Timothy Peake and his new colleagues will now train to fly to the space station and with renewed interest in the Moon, they could conceivably also get to walk on the lunar surface one day.

He reflected on how he might feel, sitting on a launch pad atop a rocket waiting to blast into space.

Meet Europe’s new astronauts It’s ground control to Major Tim

“I think it’s going to be the most incredible experience in the world, without a shadow of a doubt. The adrenalin will be thoroughly flowing at that stage,” he told BBC News.

The other new recruits comprise Frenchman Thomas Pesquet, Italians Samantha Cristoforetti and Luca Parmitano, Germany’s Alexander Gerst, Denmark’s Andreas Mogensen.

“One day hopefully I will have the opportunity to walk on the Moon. That’s the biggest dream I have at the moment,” said Mogensen, who has been working in the UK at the Surrey Space Centre.

The astronauts will begin their basic education in September for a period of 18 months. They will then get assigned to a mission for more specific training.

But it will be a minimum of 3.5 years before they can get into orbit.

Pressed about the selection of a Briton as one of the astronauts when the UK chose not to fund manned spaceflight, Mr Dordain said: “I have taken the decision after consultation and there was unanimity about the ranking of the candidates.”

Mr Dordain named British-born officials who had taken prominent roles in the running of Esa’s human spaceflight programme, adding: “You can contribute with something other than money… you can contribute with expertise.”

Nick Spall, co-ordinator of the UK human spaceflight campaign at the British Interplanetary Society, told BBC News: “The UK astronaut campaign is delighted that a British candidate has been chosen by Esa to join the growing cadre of European astronauts.

“Despite its rich heritage of aerospace experience, for many years the UK has been absent from government-organised human spaceflight activity.

“As a result, the nation has missed out on the science, industrial, exploration and inspirational benefits that this international endeavour has provided for the rest of the developed world”

Jonathan.Amos-INTERNET@bbc.co.uk

A study on recycling suggests Britons are the worst in Europe when it comes to recycling electrical equipment.

Computer manufacturer Dell found that fewer than half of UK residents regularly recycled old hardware, compared with more than 80% of Germans.

Within the UK, the Welsh are the worst when it comes to recycling technology; almost 20% have never done so.

It is thought the UK creates enough electrical waste each year to fill Wembley Stadium six times over.

Environmental consultant Tony Juniper said that lack of awareness was a serious issue.

PERCENTAGE WHO DO NOT RECYCLE E-WASTE Wales: 19% North-West England 17% North-East England 15% East Midlands 15% London 13% Scotland 13% East of England 11% South-West England 11% West Midlands 10% South-East England 9% Northern Ireland 7% Source: Dell

“Governments in every country need to make the disposal of old electrical equipment as accessible and commonplace as recycling old paper, plastics and glass,” said the former Friends of the Earth director.

In early May, mobile operator 02 looked at what electrical equipment was inside a typical home. It found that there was an average of 2.4 TVs, 1.6 computers, 2.4 games consoles, 3 mobile phones, and 2.2 MP3 players.

Historic legislation

Introduced by the European Commission in 2002, although not coming into force in the UK until January 2007, the Waste Electrical and Electronic Equipment Directive (WEEE) was European legislation designed to “reduce the amount of electrical and electronic equipment being produced and to encourage everyone to reuse, recycle and recover it”.

Jean Cox-Kearns, recycling manager with Dell, told the BBC that one of the reasons Britain lagged was because other countries had implemented the WEEE directive two years before.

“The UK had historic legislation that they had difficulty in implementing,” she said.

There are concerns that many items that are disposed of – especially computer equipment – still work but have been rendered obsolete by new technology. A number of charities actively collect IT equipment so it can be used in the developing world.

Ms Cox-Kearns acknowledged that was preferable to recycling, although she did have reservations.

“I agree we should maximise the use of computer equipment. However, we need to find out what happens to the equipment after they [the recipients] are finished with them, otherwise it is effectively dumping.”

A new optical recording method could pave the way for data discs with 300 times the storage capacity of standard DVDs, Nature journal reports.

The researchers say this could see a whopping 1.6 terabytes of information fit on a DVD-sized disc.

They describe their method as “five-dimensional” optical recording and say it could be commercialised.

The technique employs nanometre-scale particles of gold as a recording medium.

Researchers at Swinburne University of Technology in Australia have exploited the particular properties of these gold “nano-rods” by manipulating the light pointed at them.

The team members described what they did as adding three “dimensions” to the two spatial dimensions that DVD and CD discs already have.

They say they were able to introduce a spectral – or colour – dimension and a polarisation dimension, as well as recording information in 10 layers of the nano-rod films, adding a third spatial dimension.

The scientists used the nanoparticles to record information in a range of different colour wavelengths on the same physical disc location. This is a major improvement over traditional DVDs, which are recorded in a single colour wavelength with a laser.

Also, the amount of incoming laser light absorbed by the nanoparticles depends on its polarisation. This allowed the researchers to record different layers of information at different angles.

The researchers thus refer to the approach as 5-D recording. Previous research has demonstrated recording techniques based on colour or polarisation, but this is the first work that shows the integration of both.

As a result, the scientists say they have achieved unprecedented data density.

Their approach used 10-layer stacks composed of thin glass plates as the recording medium. If scaled up to a DVD-sized disk, the team would be able to record 1.6 terabytes – that is, 1,600 gigabytes – or over 300 times the quantity stored on a standard DVD.

Significant improvements could be made by thinning the spacer layers and using more than two polarisation angles – pushing the limits to 10 terabytes per disc and beyond, the researchers say.

Bit by bit

Recent efforts based on holography have shown that up to 500 Gb could potentially be stored on standard DVD-sized disks.

Holographic methods take all of the information to be recorded and encode it in the form of a graph showing how often certain frequencies arise in it.

That means that the recording process is a complex, all-at-once, all-or-nothing approach that would be difficult to implement on an industrial scale.

By contrast, 5-D recording is “bit-by-bit”, like current CD and DVD writing processes in that each piece of information is read sequentially.

That is likely to mean that recording and read speeds would be comparatively slow, but the approach would be easier to integrate with existing technology.

“The optical system to record and read 5-D is very similar to the current DVD system,” says James Chon, a co-author on the research.

“Therefore, industrial scale production of the compact system is possible.”

DVD surfaces now are “2-D”: just the position on the disc matters

Now that the method has been demonstrated in custom-made multi-layer stacks, the team is working in conjunction with Samsung to develop a drive that can record and read onto a DVD-sized disc.

Dr Chon says that the material cost of a disc would be less than $0.05 (£0.03), but there are a number of advantages in moving to silver nano-rods that would bring that cost down by a factor of 100.

For optical data storage expert Tom Milster, at the University of Arizona, the beauty of the approach is in its simplicity.

“It’s not just elegant – there are a lot of experiments that are elegant – it’s relatively straightforward,” he told BBC News.

For the moment, Dr Milster says, the equipment needed to write the data would make a commercial system expensive. However, that has not stopped the development of optical storage solutions in the past.

“For example, a Blu-ray player is not an easy system to realise; they’ve got some wonderful optics in there,” Dr Milster said. “People thought that would be pretty difficult to do, but others managed to do it.”

The tropical mockingbird’s elaborate tune puts the brown trembler mockingbird to shame

Unpredictable weather seems to stimulate chatter among birds – as well as humans – according to researchers.

A team of US scientists has found that mockingbirds living in variable climates sing more elaborate songs.

Complex tunes, sung by males to impress females, are likely to signal the birds’ intelligence.

Published in Current Biology, the findings suggest that females seek mates with superior singing skills – smart enough to survive harsh climes.

Carlos Botero, a researcher from the National Evolutionary Synthesis Center in North Carolina, led the study.

He and his colleagues compared recordings of 29 species of mockingbird, studying patterns in their songs including the number of different notes, the number of syllables and the birds’ abilities to mimic other sounds.

Carlos Botero’s approach to song recording

His team then compared weather patterns in the birds’ habitats with the patterns in the songs.

Dr Botero told BBC News that it was “very exciting” to see a strong correlation between song complexity and climate.

“The birds are not born knowing how to sing; they have to learn,” he explained. The fact that the males sing more variable tunes in a more variable climate could demonstrate the “sexual selection of intelligence”.

This means that females may be looking for a tuneful signal that their prospective partner is a good catch.

Singing challenge

Local climate patterns are good indicators of how challenging life is in a given location, Dr Botero explained.

“Survival and reproduction become more complicated when weather patterns are unpredictable because you don’t know when food will be available or how long it will be around.

“In really difficult or demanding environments you would expect females to be choosier.”

St Lucia’s white breasted thrasher sings a simple song

He added that researchers might be able to use this simple, measurable behaviour in the birds, to provide clues about the evolution of important human developments such as language, music and art.

Sandra Vehrencamp from Cornell University, who was also involved in the study said that, to fully test this explanation, the team would need to design an intelligence test for the male birds, and examine their relative breeding success.

During the course of the study, Dr Botero embarked on a solitary month-long tour of South America, seeking out elusive birds and recording their songs.

Thanks to his expedition, some key gaps in the library of birdsong at Cornell University, where he was based during the study, are now filled.

“I had to try to visit as many different countries as possible at exactly the right time – when the birds were breeding,” he said, adding that some of the remote locations he visited were like “mockingbird paradise”.

It all felt a bit ominous. With a rucksack packed with five litres of water I was struggling my way up the Hindu Kush mountain range, thousands of feet above sea-level.

Behind me was a man carrying a yellow sack – a yellow sack packed with explosives, that is.

And then on the way up the narrow path, I spotted three or four green Islamic flags marking a gravestone.

What happened there, I wondered. Well, it seemed that someone had been taking a rest – his last as it turned out – when he was struck by a rock fall.

But the reason for all the pain and high-altitude panting was simple: we were heading to the emerald mines.

Flying stones

The journey had started three hours earlier in the village of Kheng.

It was the kind of place that seemed strange even by Afghan standards.

Most of the shops were a neat row of shipping containers. And almost everyone seemed to have slips of white paper they would unwrap for you to reveal emeralds.

The stones weren’t dazzling; in fact, they looked like dull shards of glass. They only shine after they are cut and polished.

The mountains here are like Swiss cheese, burrowed with mine shafts

But for the few hundred villagers of Kheng – it meant money – and lots of it.

The source of that wealth, the mines, was above the snowline.

At first, there wasn’t a lot to look at – apart from flying stones that hurtled their way down the slopes.

But once you had caught your breath, and looked closer, you saw it for what it was: a frontier post perched high on a mountain.

Parts of the mountain were like Swiss cheese – burrowed with mineshafts.

About 300 men worked up here – living in caves, or, if they were lucky, in mud houses. Some stayed up here for weeks on end.

They worked in teams – miners, diggers, explosive experts, cooks, and suppliers. They shared the profits of any emeralds that were found.

‘Need luck’

You could buy in as part of a syndicate – and provide, say, a donkey-load of rice which would guarantee you a share.

But you needed luck in this place if you wanted to get rich.

Mohammed, the manager of one of the mines, told me that he had seen people work for 10 years and find absolutely nothing.

Some miners strike lucky quickly – others not at all

And then he had seen people mining for two weeks walking away with a haul of the precious stones.

More worryingly, Mohammed told me that 30 miners had been killed or seriously injured by explosions or fumes in the mineshafts in the past 10 years.

Unsurprisingly, there wasn’t a great deal of science or safety considerations when it came to mining here.

At the entrance to one of the operational mines, four miners, looking like sooty moles, appeared to be enjoying the daylight after hours of darkness.

Armed only with a torch, I walked into their gloom. I was forced to scramble up steep inclines. The air quality got worse and worse the further I went. It felt like walking into a smoker’s lung.

After walking for a few minutes, the noise of a drill started echoing through the rough-cut tunnel.

There were two young men. They packed the drilled hole with explosives scooped out of a plastic bag. And then fitted it with a charge.

Hasty turn

I didn’t fancy hanging about to see the explosion going off.

So I made the hastiest turn of my life and half-stumbled down the mineshaft, trying to mind my head and trying not to drop my torch.

I then shouted at Mahfouz – the BBC’s ever-patient producer – that we needed to stick together – it’s very dangerous! We can’t be messing about at times like this.

Accidents have killed or wounded 30 miners in the past decade

A few seconds later he arrived – face puffing – and calmly said: “Martin you’re going the wrong way.”

When the explosions went off – I wasn’t actually out of the mine. Instead, I was at a so-called “safe” distance.

I didn’t really hear very much – it was so loud – I just felt a rush of dust passing over my face and then my ears popped.

After the dust and my nerves started to settle, I asked one of the miners how he felt when he saw an emerald. He told me that he forgot the hardship and fatigue of a year’s work.

He then motioned to go back up the shaft to see whether the explosion had hit a seam of emeralds.

But I decided not to take him up on the offer.

To be perfectly honest, I’d had enough for one day – emeralds or no emeralds.