Is Science Popular?

Scientists often despair at the general lack of scientific understanding by the general public. And to be fair, that understanding is not brilliant, evidenced by regular surveys. I have summarised a snapshot of a series of surveys from across the world below to illustrate the point.

Percentage of people getting the right answer to a selection of science literacy questions by country. Complied from: Ipos MORI Survey, commissioned by the Government Department of Business, Innovation and Skills in 2014. Pew Research Center Poll in collaboration with the American Association for the Advancement of Science (2015) The National Science Foundation, 2014. National Science Foundation, Division of Science Resources Statistics, Survey of Public Attitudes Towards Understanding of Science and Technology, 2001, University of Michigan, Survey of Consumer Attitudes 2004. How well would you do?
The correct answers are: 1 – false, 2 – True, 3 – True, 4 – True, 5 – False

The other side of the coin is that scientists are sometimes seen as arrogant and aloof and science as unfathomably complicated. Nevertheless, similar surveys to those examining the scientific literacy of the public also report that there is a growing enthusiasm to understand it, and a huge 90% agree that it’s the sciences that will define our future prosperity. Neil deGrasse Tyson’s 2014 television series Cosmos topped 40-million viewers and Brian Cox’s recent tour sold out more than 150,000 tickets. Spurred on by all this I decided to try and write a popular science book myself but then some points of reality hit home.

In the United States, home of Young Earth Creationism and the anti-vaccine movement, popular science is still number five on the list of non-fiction genres amounting to over $155 million in sales in 2017 (published in 2019 by Statista). The genre is dominated by a few authors such as the aforementioned Brian Cox and generally speaking a celebrity figure is much more likely to get a book accepted for publication than just an everyday scientist. The publishing business is a commercial enterprise after all, bringing to mind the Monty Python Struggling Architect sketch and, “not caring a tinker’s cuss about the struggling artist”. As I embark upon a long and difficult journey in book writing I have to be realistic and accept the fact that many more books get written than ever published.

So why bother? It’s partly a matter of personal philosophy. I have always been passionate about the public understanding of science and in the past I have organised some memerorable public events (if I say so myself). Moreover, researching my own book has opened my eyes to how the general public may indeed get the view that science can be aloof.

I am a scientist with around 30-years working with isotopes one way or another but when I try to research areas adjacent to my own specific field I still end up having to compile a dictionary of technical terms. It’s an understandable problem when experts take their specific language for granted but it makes it difficult for others to cut through the jargon. Of course if they are scientific publications aimed at other scientists in the field its understandable but when the intension is for wider communication it’s a different matter. Just as an example, I was looking at a summary of how isotopes are used to follow the flow of nutrients from rivers into the oceans and came across terms such as “sediment porewater” and “aquifer” as if they were everyday terms like, drain or sewer. They are absolutely everyday terms to an oceanographer but to anyone else what do they mean? (If you’re interested I’ll let you look them up as I had to).

I would say to all scientists, new or old (old like me) dedicate just some of your time to the wider communication of your subject but watch that jargon. There’s a thirst for science and you’ll be doing your discipline a great service. And perhaps a few of you might have a try at your own popular science book …. and you never know…

… damn lies and statistics

The saying, “there are three kinds of lies: lies, damned lies, and statistics” is attributed to Mark Twain but may have originated from Benjamin Disraeli. It’s one of those phrases that has been misquoted more times than I can remember because in truth statistics is a branch of mathematics essential to understanding the world. Statistics is like a scalpel; in the hands of a skilled surgeon it can save lives, but in the hands of a serial killer it is an instrument of death. And the worse serial killers of statistics are marketing executives and politicians.

Probably the most common statistical parameter used by the news media is the average. The average size of family, or the average income; it has become so familiar it hardly gets a second thought. An average is calculated by adding up all the numbers in a data set and then dividing by the number of data points. An average can be useful as it reduces a lot of data to one easily understood number, but it can also mislead for precisely the same reason. The problem with average is that it says nothing about the way the data are distributed. An average is most useful when the data are what is known as a Gaussian, or normal distribution, whereby they are evenly distributed and the spread of numbers is bell-shaped (see Figure-1).

Random events such as the height of individuals in a country, or the weight of grains of sand on the beach will form a classical Gaussian distribution. Other data, such as earnings in the UK are not Gaussian, they are skewed to one side. To take an extreme example to illustrate what I mean, fifty people might have an average salary of £30,000 per year but that average could equally arise from all fifty earning £30,000 each or from forty-nine having a salary of one pound per year and one person having a salary of £1,499,951.

I want to be careful not to make political points rather than focus on the use – or misuse – of statistics. All politicians, in my experience, have selected statistics to suit their purpose at one time or another but it just happens that a particular example has recently come along. There was a Tweet from UK politician Dominic Raab saying real wages are rising at the fastest rate for 10-years (Figure-2).

The plot shows average weekly earnings versus year. It shows the latest average weekly wage as £495, which is equivalent to £25,740 per year. The first thing that strikes me is that the graph is pretty flat across 2016-2018 and to my eye, the fastest rate of increase was around 2015. The claim that wages are rising at the fasted rate for 10-years therefore seems to me to be somewhat ambitious based upon the graph in the Tweet.

Nevertheless, putting the basics of graphical interpretation to one side, the use of average is fine if the data have a Gaussian distribution such as in Figure-1 but, as I’ve already said, UK earnings are not Gaussian. Take the 2013/14 earnings statistics for example (Figure-3). In such cases, two other parameters are more meaningful: the median and the mode. (For a Gaussian distribution, the average, median and mode all coincide, but these parameters part company if the spread of data leans one way or another).

The median shows the point at which the data are centred, that is the mid-way point. Since those earning lower wages are more numerous than those earning higher wages, then the average will always be a higher number than the median. The mode sits at the apex of the data, coinciding with the most frequently occurring number. For the 2013/14 statistics the mode was around £16,500 per year and given the distribution pattern it’s going to be a lower number than the median and the average. You can see the mode of £16,500 is around 56% of the mean of 29,172, a very significant difference. In short, the use of average with non-Gaussian wages data will always give a more favourable number than the median and mode. This is important because the use of average in this case hides the income for most wage earners.

Does this really matter? Yes it does. If a democratic society is to have informed opinions then at the very least those who are elected to office should present a complete picture of what’s happening in the country. We hear a lot about fake news – which is frankly, just stuff made up. The misuse of statistics however, is much more subtle. It can give an air of authority but also be perniciously misleading. Whether the politicians are spinning the statistics to suit their preconceived beliefs or whether they are just ignorant, I will leave to the reader to decide. In the meantime, beware of political statistics and remember Mark Twain.

Old in a young age

The stereotype of people of my age is someone who, when asked to press “any key” on the computer, asks, “where’s the anykey”. I’m not like that. Although my children might smile when I claim to be technically savvy, I like technology and I’m generally the antithesis of a Luddite. Just recently, for example I was introduced to Apple Pay and the idea of holding all my plastic credit and cash cards in a virtual wallet on my iPhone, I find quite inspiring.

I am nevertheless of an age where I can remember a world long before the internet – actually even before the common use of the transistor. I thought perhaps I’d take a short journey down memory lane so these young whippersnappers who take modern technology for granted, understand what it was like – all within a single lifetime.

My first memory of virtual money was in the 1960s when the Co-op man came to visit. In those days it was always a man. He came round once a week and my father deposited money into a Co-operative fund. Co-operative stores were not little corner shops but places where us working class bought clothes, furniture, Christmas presents and anything else you could think of. Money deposited in the Co-op fund was recorded in a book – yes by pen and ink – and then placed into the Co-op man’s brown leather satchel. He carried a lot of cash around and “the Co-op man’s been robbed again”, was an often heard phrase. When you wanted to spend some of the fund, he issued you with Co-op money, also from his satchel.

These were tin tokens that you could then exchange for goods in Co-op stores. I think the idea was you got discounts if you used Co-op money as opposed to real money, which of course they still accepted. That was a time of mostly cash. My father got his wages paid in cash and although cheques were about, many people didn’t have bank accounts. Down the street where I lived, cheques were considered a little bit posh.

I got a bank account when I started work in the 1970s. To get cash meant queueing up in the bank and handing over a cheque. Banking hours were 10 am to 4 pm and so it wasn’t unusual to run out of spending money. By the 1970s a new innovation arrived – the cash machine. They were available 24 hours a day – a huge improvement, but they were nevertheless, a little different back then.

The bank issued a plastic punch card which dished out a set amount of money – typically £10 from the cash machine. They retained the card and then posted it back to you in the mail to arrive a few days later. Pause for a moment and imagine that – a snail mail cash card.

I’ll skip the part when transistor radios first arrived. In those days you needed a radio licence, just like a TV licence today*, and I remember inspectors from the BBC going around sunbathers on the beach asking if they had a licence for their transistor radio. I’ll mention that I also remember when telephones became common. These were big black heavy devices a long way from today’s mobiles. My next-door neighbour had a telephone installed, the only one in the street. They were, my father said, getting a bit above their station. My mother didn’t like telephones, she said it would ruin the art of letter writing.

Credit cards came to the UK in the form of an ACCESS card – “your flexible friend”. To use it in the shops, it had to be placed in a little machine that took an imprint which was followed by a physical signature. Credit card fraud rose dramatically and over time, other innovations were introduced such as PINs then chip and PIN.

Internet banking came in by the 1980s. I recall many saying it wouldn’t catch on because it was too impersonal. I remember the actor, Robbie Coltrane, advertising internet banking, telling everyone it was liberating. I guess it was but remember this was the time of dial-up modems with speeds equivalent to the rate grass grows. Email was born around the same time (in common use anyway) but again, there were some who resisted because they thought it would replace the telephone and ruin the art of conversation. I worked for ICI at the time and they adopted one of the first email systems called all-in-one. It only worked internally within the company but we loved it because you no longer had to write a memo and put it into the internal post.

The first computer I bought was an Olivetti with, what was then, a massive 100 MBytes of memory. You might laugh but this was when word processors replaced the old typewriter and gallons of correction fluid. It was bliss, I can tell you.

So as I now add my cards to Apple Pay and it does it by scanning the card via the phone’s camera, I spent just a moment remembering what life was once like. And I wonder, when my grandchildren get to working age, what will things be like then? Impossible to say, I think, but I hope I live to see it because I am, in truth, a bit of a technology geek.

* if you are from the USA it might surprise you to hear you need a TV licence in the UK, when you are from a country where a gun licence is optional.

A Plastic Revolution

Plastic and the pollution it causes is in the news. There’s the plastic free challenge and the UK government has set aside £60 million to fight plastic waste.

I could not agree with all this more whole heartedly and have tried hard to reduce my personal use of plastic. It’s only when you take time to think about the amount of plastic that get’s thrown in the bin that you realise how bad the problem is. Just as an example I no longer buy laundry detergent in plastic bottles and have switched to powder in a cardboard box. Having said all this however, just recently I disposed of mounds and mounds of plastic, over which I had no control.

I have just had a new kitchen installed. The old one was 20 years old and was certainly showing it’s age. The majority of the materials in the new kitchen are recyclable being mostly wood products from renewable sources. Indeed the kitchen suppliers advertise their environmentally friendly credentials on this basis. All this seem laudable but nevertheless misleading because the amount of plastic packaging that comes with all the “environmentally friendly” stuff was overwhelming.

All the units where wrapped in plastic. The doors were covered in a plastic film that had to be peeled away and every cabinet came with it’s own plastic bag of screws. The hob was wrapped in enough plastic bubble wrap to choke a blue whale. By the time the kitchen was installed there were no fewer than dozen bags full of plastic waste.

The reason given for all this packaging is of course to protect the customer’s expensive purchase, but I am just not convinced. Everything in the old kitchen had to be packed away and I was tempted to purchase plastic bubble wrap for glasses and crockery. Instead of plastic however, I found a paper-based alternative. A sort of corrugated cardboard made from recycled paper that goes by several names, including Ecorap, Corrugated papercan and Cushion Paper amongst others. It was little more expensive, but in terms of the cost of a new kitchen it was trivial.

This exorbitant use plastic packaging doesn’t just apply to new kitchens, it’s everywhere you look. Every new appliance, furniture or household item is likely to be packed in either bubble wrap or contained in a plastic bag. I am therefore left with the felling that even if I reduced my own personal plastic usage to zero, it would be but a carrier bag in the ocean compared to its industrial use. Avoiding detergent in plastic bottles seems an almost pathetic effort in context of the reliance on plastic in packaging. Industry will continue to use plastic packaging because it’s cheep and convenient, until such times that environmental taxes change that attitude, and that takes government action and the will of the people!

You say 'aluminum,' I say 'aluminium' let's call the whole thing off

News headlines are buzzing over Donald Trump kicking off a trade war. In amongst the smoke and mirrors of politics one thing is very clear, the name of the 13th element is pronounced differently in North America and Europe. In Europe the discussion surrounds US tariffs on steel and ‘aluminium’, while in North America it’s steel and ‘aluminum’: why the difference you may wonder? I am told it’s a classic case of the United States messing up the English language, like they did when they removed the U from color. But is this true?

Tracking the name of the 13th element back to its origins, it was first called ‘alumium’ by the English chemist Sir Humphrey Davy in 1808. Then in 1812, in his Elements of Chemical Philosophy, he called it ‘aluminum’, the same as in North America today. The use of ‘aluminium’ was subsequently adopted in Britain because it was considered to have a more classical sounding name.

Both ‘aluminium’ and ‘aluminum’ therefore evolved from a common extinct ancestor, ‘alumium’. Both terms are officially accepted today and it’s hard to argue one is more valid than the other.

And for the record, the origin of ‘color’ is from the latin ‘color’ and colour came from the Anglo-Norman ‘colur’. I’ll leave the final comment to the philosopher Bertrand Russell who said, “It is a misfortune for Anglo-American friendship that the two countries are supposed to have a common language.”

A surprise from old lead piping

I’m having construction work done on my house. The chimney breast in the kitchen is being removed to open out the space, which has turned out to be an arduous and dirty job. There have however, been some interesting surprises. At the back of the chimney breast I found an old water boiler, probably close to 100-years old, along with some lead piping. Lead from the 1920s is interesting for an unusual reason. To explain, let me switch stories for a moment to a laboratory where I once worked.

My career has, more or less, been spent measuring radioactivity emitted from medical radioisotopes. I’ve focused on measuring tiny amounts of radioactivity using various highly sensitive techniques. One technique, called autoradiography, involved tagging biological material with a radioisotope and then visualising its physiological distribution by exposing the sample to photographic film. The levels of radioactivity are small and the film is insensitive and so exposure times for the photographic plates are very long – up to several weeks. The problem with this is that radioactivity is everywhere. It comes out of the sky as cosmic radiation and it even emanates from the human body from radioactive carbon and potassium. Over long time periods the photographic plates become fogged from this background radiation.

To get around this problem, the photographic plates are placed in a box made of lead. But then there’s another problem. The atomic bomb tests of the 1960s injected small amounts of radioisotopes into the atmosphere which become trapped in molten lead as it solidifies. This small amount of radioactivity was enough to fog the plates when exposures were particularly long. The lead boxes shielding the photographic plates were therefore constructed from pre-1950s lead, hammered into shape without melting. One supplier of these boxes told me they got most of their lead from the roofs of old churches during demolition. That way they could verify the age of the lead, which was often from the Victorian age.

The lead piping from my kitchen would have therefore served well for an autoradiography box but there’s probably not enough for anyone to be interested. In the meantime, I’ve kept a sample of the piping and I’ll encase it in plastic as a reminder of a bygone age.

New migraine drug hails the future of therapeutic development

If you follow the science sections of the general media, you may have seen reports of a new migraine drug called Erenumab. The drug is not yet on the market but shows promise having just come through the final phases of clinical testing.

Erenumab, made by Novartis, is one of several similar drugs being developed for migraine, including Eptinezumab (Alder Biopharmaceuticals), Fremanezumab (Teva) and Galcanezumab (Eli Lilly). All good news for migraine suffers but these drugs are also examples of modern drug development and that’s the story I want to tell here.

As a general concept, drugs are designed to correct, or adjust, some biochemical or physiological malfunction within the body. This requires the drug to interact with a biochemical process, either activating it, or blocking its action. Making therapeutics which interact with specific biochemical targets – or in the jargon of pharmacology, to develop drugs with high specificity, has been a major goal of pharmaceutical science for several decades. One of the founders of chemotherapy and winner of the 1908 Nobel Prize for Physiology, Paul Ehrlich coined the phase “magic bullet” to describe the concept of specificity. Achieving high specificity has been more challenging than Ehrlich expected however, as in reality rather than a sniper’s bullet, a shotgun blast would be a better metaphor for many drugs. And like a shotgun blast, non-specific drugs hit many unintended targets leading to unwanted side effects.

Traditional treatments for migraine have utilised drugs developed for other indications. Lisinopril, for example, can be prescribed as an anti-migraine drug, although its primary use is to treat high blood pressure. Drugs used for other indications such as depression and epilepsy are also sometimes used as migraine treatments, in effect exploiting their non-specificity for alternative uses. This new range of migraine drugs is different however, in that they were developed to block a specific target; that target being a peptide called calcitonin gene-related peptide, or CGRP for short.

Produced within nerve cells (neurones) it comprises 37 amino acids and comes in two forms known as alpha and beta. As an aside, capsaicin in chilli (the subject of another blog post ) mediates the release of CGRP which is one reason for its association with pain. Neuronal production of CGRP has also been correlated to the onset of migraine and therefore moderation CGRP was identified as a suitable drug target.

But how is a drug developed to block CGRP alone, and not other related peptides? To answer this, we turn to the immune system and the way it fights infection. If you want an example of biochemical and physiological complexity, then look no further than the immune system. Since I have to avoid the tomes of textbook explanations, I’ll over-simplify enormously and just explain that in response to infection the immune system produces proteins called antibodies. The three-dimensional shape of antibodies specifically recognises other proteins on the surface of infecting organisms, where they lock-on acting like flags to white blood cells which then attack and destroy the invaders.

Evolution has honed antibodies to be extremely specific as it’s important they attack invading organisms and nothing else, such as your own body tissues. Drug developers have exploited this high specificity so that instead of locking onto infective organisms, the antibodies bind to, and block, specific biochemical targets. You might say they are the laser guided equivalent to Ehrlich’s magic bullet. The antibodies are biologically engineered in sterile cell cultures with each cell being an exact copy, or clone, of each other. This gives them their name of monoclonal antibodies – or mABs for short. You may have noticed that the names of all the new migraine drugs above end in mab – indicating their origin.

Especially designed to block CGRP with great specificity, the new mAB drugs are the pinnacle of therapeutic pharmacology. Before we get too smug however, remember that the interactions within the human body are extremely complex and it’s impossible to predict all the implications of therapeutic intervention. Little is known of how CGRP is regulated for example, and so there’s always the possibility that some unforeseen side effect lurks in the fog of complexity. Moreover mAB-type drugs have to be injected as they are not absorbed if taken orally. Development of orally-administered mABs is something drug developers are now attempting but there’s still a long way to go. The job of pharmaceutical development is not over quite yet.

Now is not the time to be complacent about plastic pollution

Some of us are old enough to remember when a polyester suit was fashionable. Although still used in clothing today, polyester has diminished in appeal since the 1970s. There is however, plenty of polyester still around but in a different guise as PET or polyethylene terephthalate which is the major constituent of plastic drinks bottles.

Patented in the 1940s as a thermoplastic polymer, PET provided a cheap and readily available packaging material. That economic dream however has now turned into an environmental nightmare as a mountain of discarded plastic has built up across land and sea.

The news media over the past few days have hailed the accidental discovery of a mutant enzyme that breaks down PET as the solution to the plastic pollution problem. As a biochemist I thought the general news media was somewhat short on detail and so I thought I’d take a closer look.

PET comprises repeating units of a chemical called terephthalate and ethylene glycol joined together with oxygen-containing links called esters. Esters and related chemical bonds are common in nature and are generally vulnerable to enzymes collectively called hydrolases, which include esterases, lipases, and cutinases. They all add water across chemical bonds resulting in cleavage of the individual molecules. Blood, for example, is rich in esterases that break down a variety of chemicals, including neurotransmitters such as acetyl choline. The nerve agents recently featured in the news, work by stopping esterase from breaking down acetyl choline thus interfering with normal nerve function.

The trouble with PET however, is that because of its molecular structure the bonds are not accessible to hydrolases although the exact molecular process of enzymic PET hydrolysis is not clearly understood. This doesn’t mean PET is immune from biodegradation, it just means it happens very slowly. All enzymes are what are known as catalysts, in that they don’t react directly rather than just speed up existing chemical reactions. The discovery of the mutant enzyme in the news is just such a catalyst that speeds up the rate of hydrolysis of PET. The effect is highly significant, speeding up the natural process from hundreds of years to just days.

This new mutant enzyme is called PET hydrolase (or PETase for short) and was found in a species of bacteria called Ideonella sakaiensis that lives in the plastic mountains of Japan. This bacteria can live off plastic, breaking it down and using it as a carbon source in much the same way we utilise sugar.

It is however, not the first biological weapon against plastic to be discovered. Last year there were reports that wax moth larvae could break down PET although the effect was likely to be due to bacteria living in the worm’s gut.

The big question is, will these discoveries solve the problem of plastic pollution? The answer is probably, but there is always a lag of many years from the basic science until development of effective technologies. In the meantime, now is not the time to be complacent and reducing plastic consumption remains an important endeavour.

Hot stuff

A 34-year-old man has ended up in hospital after eating a Carolina Reaper chilli.

I have some sympathy because during my first post-doc, I was working in a laboratory at the University of Glasgow where a researcher was extracting capsaicin and some related compounds from chilli peppers. Capsaicin is the chemical that gives chilli its hot flavour and it’s pretty powerful stuff which is why it’s used in pepper spray. This particular researcher made the mistake of dropping a vial of capsaicin, which broke on the floor and spread into the laboratory. We had to evacuate in a manner resembling a teargas attack.

Capsaicin is not just the macho ingredient of curry, it is also used medically. Dermal patches containing capsaicin are used to treat neuropathic pain. It is also used under more dubious credentials such as oral tablets to treat osteoarthritis, and some even claim it cures cancer. Neither, in my view has any validity.

Brain cells and the atomic bomb

Reports appeared in the press recently proclaiming that humans produce new brain cells throughout their lives (for example, The Guardian ). This account appears to contradict previous reports such as

in The Conversation and in Discover Magazine

Don’t we all wish these scientists could make up their mind (pun intended)?

The most recent accounts that the brain generates new cells throughout life did not surprise me as it’s something that has been known for some time. The surprise was that the newspapers thought this was some new breakthrough. I had the enormous privilege of sitting on the Scientific Advisory Board of the Karolinska Institute’s Human Regenerative Map Project where this very subject was studied several years ago. Before I say anything about the results, let me explain the background to the experiments because that, at least for me, is the really interesting part.

The atomic bomb tests of the 1960s released radioisotopes into the atmosphere. One was a radioactive isotope of carbon called carbon-14. The amounts released were surprisingly high as the atmospheric concentrations almost doubled from the pre-1950s levels. (The absolute amounts are still tiny – in the parts per trillion and so there’s no need for alarm). Over time carbon-14 sequestrated into the oceans and following the 1963 treaty to limit testing, the levels fell again. The Figure shows a plot of atmospheric carbon-14 versus year which has become known as the bomb pulse (units of percent modern carbon represent atmospheric carbon-14 concentrations).

During the time of the bomb pulse everyone on Earth accumulated a little extra carbon-14. Let’s take some hypothetical person born in 1963 at the peak of the bomb pulse, we’ll call her Alice. When she was born, the cells of Alice’s body contained peak levels of carbon-14. As time went by and Alice grew up, some cells in her body died away to be replaced with new ones. The new cells, being formed at a later time along the bomb pulse had lower levels of carbon-14. Other cells in her body lasted much longer. In fact some cells in her body may never have been replaced, so they held onto the 1963 levels of carbon-14 to the day she died. This means that the levels of carbon-14 in the cells are proportional to the rate at which particular cells types are replaced by the body over time (known as the turnover rate). If Alice died in 2012 and some given cell type in her body had levels of carbon-14 equal to that of 1963, then the conclusion would be that these cells were the same as those she was born with, at least for the 49 years of her life. If another cell type dated to 2012, then these cells were recent and so were being replaced rapidly within her body.

As part of the human regenerative map project, samples of tissue were taken from consenting Swedish individuals after they died. The dates of birth and death had been recorded and so all that was necessary was to measure the carbon-14 in the tissue and the cellular turnover rates could be calculated. Of course it wasn’t really that simple because cells contain a plethora of substances all of which might be replaced within the body at different rates. To get specific results, it was necessary to measure carbon-14 in the cell’s DNA, which is technically very challenging. An extremely sensitive instrument called an accelerator mass spectrometer (AMS) was used to do this and a picture of an AMS control console decorates the home page of this blog.

Incredibly therefore, the death and destruction following development of the atom bomb has now been put to a much more beneficial use towards understanding the human body.

Before I leave this post, I should mention what the carbon-14 data told us. To do so, I need to give a little technical background. The hippocampus is the region of the brain involved in consolidating information from short-term to long-term memory. Within the hippocampus sits the dentate gyrus which is believed to be involved in new episodic memory and problems in this area are stereotypical of the older generation. The functioning nerve cells of the hippocampus, and the brain generally, are called neurons but unlike the majority of other cells in the body neurons cannot divide. This is itself evidence that brain cells are never replaced but as ever, let’s not make superficial conclusions and look a little deeper and consider where neurons come from.

Track them back and they originate from neural stem cells which then differentiate into a sort of primitive nerve cell called a neuroblast. Neuroblasts are then committed to divide and differentiate into neurons. Neurons themselves cannot divide and so when they die they are gone forever but is it possible for new neurons to be formed from the differentiation of neuroblasts? This has been a point of debate for many years bearing in mind there is a large number of neuroblasts in the dentate gyrus of infants that rapidly decreases and are virtually absent in the adult. This somewhat circumstantial evidence pointed towards minimal neurone regeneration at least in this area of the brain and so the old adage may well be correct.

What was actually found through measurement of carbon-14 from the bomb pulse, was that around a third of the cells of the hippocampus are subject to exchange, which is approximately 1.75% per day. This is good news for those of us who have more years behind us than to come, in that there was little decline in this regeneration with age.

There is however another side to this story. Within the forebrain of vertebrates sits the olfactory bulb. As its name implies, the function of the olfactory bulb relates to smell. The olfactory bulb in rodents changes markedly after giving birth as a result of the generation of new neurons. The same is observed in adult monkeys and is believed to be related to olfactory signals from the new born. The same is not true in humans however, and the neurons of the olfactory bulb date pretty much to the day you were born. Don’t ask me why, I don’t know. Perhaps humans have evolved other ways of recognising our young than smell and so it is no longer necessary but this is of course, pure speculation.

So the answer to the question, do humans produce new brain cells throughout their lives? It depends on which part of the brain you’re talking about. Now isn’t that a surprise.