Category Archives: Science

The evolution of butterfly eyespots

Here’s an interesting observation I made a few years ago that I think makes a good illustration concerning the evolution of eyespots on butterfly wings.
Below is an image of a peacock butterfly, with its very obvious eyespots.

Next, here’s an image of the top edge of the peacock’s upper wings, with beneath it an image of the top edge of another butterfly’s wings that look extremely similar. You can make out the same type of eyespot pattern on both sets of wings.


The second butterfly in the image above isn’t a peacock however, as you can see from the image of the whole butterfly below. It’s a small tortoiseshell, and it doesn’t have eyespots at all.



Assuming that the two species evolved from a common ancestor, how is it that the butterflies might have evolved in such a way that their wing patterns (at least along the top edge) are so similar yet so different?

Here’s a theory.

The common ancestor of the tortoiseshell and the peacock started without eyespots – with wings that were perhaps similar in patterning to the present day tortoiseshell’s (at least in the region of the wings that we’re dealing with).  Small variations to the colouring of the patterning on the wings of some of the butterflies then turned the abstract patches at the top of the wings into what we interpret as eye shapes. These eye shapes turned out to be very useful for the survival of the butterflies that possessed them, and thus the eyespot pattern was passed on and reinforced through the generations. Thus the evolutionary line that developed into the peacock diverged from the line that evolved into the tortoiseshell. It’s important to emphasise that the patterning’s resemblance to eyes is purely fortuitous: it’s nothing more than a small random deviation from the abstract patterning that the tortoiseshell butterfly still has – a bit of light colour added here, a bit of dark there. It’s just that this particular small variation in patterning has such an obvious effect, because most creatures are attuned to homing in on eyes (or anything that looks like eyes). Other small random deviations to the patterning would go almost completely unnoticed.

This explanation for the evolution of the eyespot echoes very nicely the theory of the evolution of the eye itself, in which random variations in a species’ makeup eventually lead to the evolution of what otherwise seems to be a near miraculous organ (See The evolution of the eye. )

It’s also possible that evolution took a different route, and that the common ancestor of the tortoiseshell and the peacock both actually possessed eyespots, and that through evolution the tortoiseshell gradually lost its spots. This however doesn’t explain how the butterflies both acquired their eyespots in the first place. I expect that it would have been through a process very similar to the one that I’ve just described.


One last thing.

A while ago I was watching a peacock butterfly sunning itself on the ground. I was watching it through a pair of close-focus binoculars, so that I has a very close-up view of the insect. It was vibrating its wings, which insects often do when they need to warm up their flying muscles. Through my binoculars the extremely close-up view of the rapidly vibrating eyespots on the wings looked truly sinister and scary. If I’d been a predator (which by definition would mean that I’d be very close to the butterfly and would be very much aware of the vibrating of the eyespots) I’d have fled. So vibrating wings may not only be good for warming up wing muscles, but also for warding off predators (which would be particularly useful when the butterfly hadn’t warmed its wing muscles up enough to be able to fly away itself).





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What are the odds that you exist? The fallacy of your specialness.

What are the chances that you exist? That is, you personally.
I’ve heard this question posited many times.
I think Richard Dawkins mentioned it in one of his books, or maybe in an interview, and I’ve recently seen it on the back cover of the new book by Dr Alice Roberts titled “The Incredible Unlikeliness of Being“, (the book that gets my prize for the wittiest book title of the year, being based, in case you don’t know, on the book title “The Unbearable Lightness of Being” by Milan Kundera).

The question is usually asked in something along the lines of: what are the chances that your mother and father would meet? Maybe your mother turned left instead of right at a street corner and bumped into the man who was later to become your father. What are the chances of that?
And what are the chances that your grandparents met, and that their parents met, and that their parents met before them?
The chances are surely vanishingly minute.
Yes they are.
Your existence is statistically almost infinitely unlikely.
(Hence the title of Alice Robert’s book, The Incredible Unlikeliness of Being.)

However, as incredibly unlikely statistically your own personal existence is, it isn’t actually incredible in the sense of being beyond credibility.

As far as I can work out, the statistic concerning the likelihood of one’s own existence is a trivial or mundane statistic – in that it may be true but it has little significance.

Here’s an analogy to show what I mean.

I’m going to type a list of thirty random numbers.


There it is.
Now, what are the chances of that row of numbers being those particular digits in that particular order?

The chances are one in 1,000,000,000,000,000,000,000,000,000,000.

(A simpler example of the same principal is that the chances of writing any specific list of digits that’s only two digits long is one in a hundred – the combinations being from 00 to 99, or in other words a hundred possible combinations.)

You probably don’t think that it’s incredible that I’ve just written down a list of numbers that has only a one in a million million million (etc) chance of existing. I had to write down a list of thirty digits after all, and every list of thirty digits has the same incredibly low chance of being written. But one of them is inevitably going to be written.

It’s the same with people.
The chances of you existing may be almost vanishingly unlikely, but if it wasn’t you who existed it’d be someone else, in the same way that if it wasn’t that list of thirty digits it’d be a different one. (Your mother may have turned right at the street corner instead of left and bumped into a different man who would father a child who wasn’t you, while your father (who now wasn’t bumped into) continued on his journey to a work appointment at which he would meet his future wife).
We’ve got to end up with someone rather than no-one. It just doesn’t have to be you.
Or if it doesn’t have to be someone it has to be something. Maybe a descendant of the dinosaurs (because the asteroid missed), or more likely something that we can’t even envisage because there are just so many possibilities – just as there are so many possibilities when it comes to writing random thirty digit lists of numbers.
We haven’t even considered random million digit lists of numbers yet. Let’s not bother – just because something’s vanishingly unlikely doesn’t make it special.

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The Rosetta comet probe – alternative designs for the Philae lander

The Philae lander has now left the Rosetta comet-chasing space probe and is heading for a rendezvous with the comet in six hours or so.
Watching television reports about how the probe is designed to land on the comet doesn’t exactly fill me with confidence. The three-legged design looks as though it wouldn’t take much to tip it over, and the surface of the comet certainly looks as though it’s littered with numerous trip hazards.
I can’t quite work out why the designers didn’t go for a more terrain-forgiving landing mechanism that had more latitude for error. Obviously there are issues of cost restraints and factors of technical feasibility that I know nothing about, but here are a few suggestions of my own.
Ideas that come to mind are such things as using a harpoon to anchor the craft to the comet before the craft actually touches down, then the craft could reel itself in no matter what the lie of the land. This method would obviously need the material of which the comet is composed to be harpoonable, which may be why the method was rejected. (The craft actually does have anchoring harpoons attached, but these are designed to be deployed after it’s landed, so they are more of a back-up system than a primary device).
Other landing systems that may have been appropriate could involve flexible or cushioning landing mechanisms such as inflated pillows (that deflate on impact), widely splayed, long, articulated legs (much more flexible and articulated than the rather rigid-looking ones that the spacecraft actually has) that buckle on impact to take on the topography of the landing site, or even the astronautical equivalent of long chains with grappling hooks that could fan out around the craft as it comes in to land to snag on any suitable features of the terrain.
In all of these designs the scientific instruments in the probe could be housed in a self-righting capsule to ensure optimum orientation after touchdown. The design of the probe that’s actually going to land in a few hours’ time doesn’t seem to have any system for realigning itself if it lands awkwardly.

Anyway, Philae is due to land soon, so I hope my misgivings prove to be unfounded. I’m sure the landing site that’s been chosen for the probe is the best possible site that’s available, so – fingers crossed!.

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Why Women’s Menstrual Cycles are Linked to the Moon

Are women’s menstrual cycles affected by the moon?
A menstrual cycle does after all span the same amount of time as a lunar cycle. The word menstrual actually means monthly, and a month is based on a lunar cycle (so it should maybe be called a moonth).
Discussion about the subject often revolves around the fact that the moon creates the tides in the oceans, so logic suggests that it probably creates tides in people too, affecting their bodies in interesting ways – and affecting their brains too, such as turning some of them into ‘lunatics’ or ‘lunar-tics’ at the full moon.
This theory falls down due to the fact that the moon’s gravitational pull on objects on the earth is extremely small. It only affects the oceans to the extent that it does because there’s a lot of ocean to affect – so you notice the effect at the edge as the water goes up and down the beech. You don’t notice the tide in a puddle on the pavement after a shower of rain (and the puddle definitely doesn’t travel several metres as a single entity across the ground following the pull of the moon, covering the same distance as is covered by the tide on a beech). In fact the gravitational pull of a tree outside your house is much greater than the pull of the moon, so the pull of the moon is effectively swamped by everyday objects here on earth.
If the moon does have an influence on menstrual cycles I think that the reason is probably quite prosaic – it’s to do with the brightness of moonlight.
Why would the brightness of the moon affect menstrual cycles?
Because it affects what people in the days before the invention of artificial light could do at night.
The full moon lights up the night sky quite significantly (and conversely, the new moon results in ink black nights on which you can’t see your hand in front of your face). When there was a full moon people could move around at night; when there was no moon they couldn’t (or at least could only do so with much more difficulty). In our modern world we can easily forget this fact, but in the world before artificial light it had a huge impact on after-dark activity.
There are probably numerous scenarios that can by posited in which moonlight and the resulting nght-time activity of humans could play a part in influencing menstrual cycles – here’s one that I’ve devised (as I’m sure have others).

Primitive humans used to live in small family groups, often in competition over territory with neighbouring groups.
Within any particular group it would be common for males and females to mate. Unfortunately, because the member of the group were almost definitely related to each other one of the consequences of mating within the group would be in-breeding, with the resulting degeneration of the genetic stock. Ideally it’s best to mate with someone who isn’t a particularly close relative in order to ensure robustness in offspring due to genetic variation.
It would be preferable for a female in a group to mate with a male from a neighbouring group (even though the members of the two groups would probably all be related to each other to some degree, but not as closely as within each individual group). Unfortunately mating with a neighbour would probably be difficult due to the fact that the groups were in competition for land and resources to the extent that when the groups met the result would be conflict.
The only way in which a female from one group could mate with a male from a different group would be if they were to meet away from the gaze of other group members, and that would probably never happen while the members of the groups were wandering around during daylight hours when it was easy for them to keep an eye on each other.
Meetings between males and females from neighbouring groups were much more likely at night, when it was harder for group members to see what other group members were doing. Not only that, but meetings were much more likely on moonlit nights, when nocturnal activity was at its height.
As a result, females would be much more likely to bear offspring from members of neighbouring groups
following meetings on those moonlit nights.
How would this make women’s menstrual cycles synchronise with the phases of the moon?

In order for a liaison to bare offspring the female has to be fertile at the time of mating. As a liaison between a female and a male from different groups is more likely at the time of the full moon it follows that for such a liaison to bare offspring the female would have to be fertile at the time of the full moon.
The offspring of liaisons between members of neighbouring groups would, on average, tend to be more robust that the offspring of liaisons between members of the same group, and would thus be more likely to grow to adulthood and breed themselves. Thus the characteristics of females who are fertile at the time of the full moon would be more likely to survive into future generations – with one of these characteristics would be the tendency to be fertile at the time of the full moon.

Not only is it advantageous for a female to be fertile at the time of the full moon, it’s equally important for the female to not be fertile at other times of the lunar cycle, when she’s much more likely to mate with members of her own, related group. So, for instance, it would be a disadvantage to be fertile twice during the lunar cycle (especially as, for one of the fertile periods to coincide with the full moon the second fertile period would probably coincide with the new moon, when the sky is at its darkest and mating between members of the same group would be most likely).

I have to impress that I’m not suggesting that the appearance of the full moon in the sky would make the members of different groups actively go out and seek members of other groups to mate with (but equally I’m not saying that that wouldn’t be the case). All I’m saying is that the time of the full moon would be the time when members of different groups mated and thus had offspring who were more robust than the more inbred offspring of mating within the same group. The process involved is simply evolution at work. No special lunar powers are evoked or involved. It’s all to do with the slight advantages of genetic robustness brought about by the production of offspring from the larger gene pool that is available at the time of the full moon.

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Are we alone in the galaxy? Brian Cox thinks so.

Is there anyone out there?
Are there other stars than the Sun in the galaxy that are orbited by planets that support intelligent life?
Brian Cox doesn’t think so.
In his BBC tv series on the human race’s place in the universe – Human Universe – he gives his reasons.
I’m not sure that I agree with him, but here’s his thinking.
In the 1940s Hungarian/American mathematician John von Neumann came up with the concept of self replicating machines (which he called universal constructors) – machines that could reproduce themselves. (Having just stated that von Neumann came up with the concept I’d like to qualify that statement with the observation that most concepts are thought up independently by several people, it’s just that only one of them usually gets the credit).
If such machines were to be launched into space they could land on asteroids, planets etc and mine the mineral resources there, using the minerals to construct replicants of themselves. By a process of asteroid/planet hopping they could thus multiply and spread out through the galaxy. It’s estimated that by such a process the whole galaxy could be colonised in ten million years.
If an intelligent alien race had at some point over ten million years ago (that is, for most of the history of the galaxy) decided to create such machines they’d have spread throughout the galaxy by now and we’d be able to see evidence of their existence.
But we can’t, so they didn’t.
This, according to Brian Cox, is the clincher when it comes to deciding whether advanced, space-going civilisations have existed before. He thinks that because the concept of self-replicating galaxy-colonising machines constructed by advanced alien civilisations is possible in principle we have to construct an argument for why we don’t see them – and he can’t think of any such argument.
He concludes that therefore it’s probable that there never have been advanced space-going civilisations in the galaxy up until now – until we came along.
Personally, I’m slightly uncomfortable with the reasoning here. The lack of evidence of self-replicating alien technology in our vicinity seems like a rather tenuous reason to dismiss the concept of intelligent alien life-forms.

In the tv programme Brian Cox stated that he couldn’t think of any reasons why where wouldn’t be evidence of alien self-replicating machinery, so I assume that he’s weighed up the arguments and has dismissed the ones that give reasons why advanced civilisation may exist and yet may not send out self-replicating machines. Unfortunately he didn’t give us any examples, which is a shame.
I can think of a few off the top of my head. They’re probably all flawed, but here are three of them.
Reason one: advanced alien intelligences have existed that are capable of making self-replicating galaxy-colonising machines, but they decided not to. They may have realised that a galaxy that was full of their machines, self-replicating endlessly – long after the civilisation itself had died out – was not a good idea. They’d probably have tried prototype self-replicating machines on their home planet first, with either inconvenient or dire consequences.
Reason two: the advanced alien lifeforms just weren’t interested in galactic colonisation, for either psychological or practical reasons.
Reason three: self-replicating machines have indeed spread throughout the galaxy, but the machines are hidden from our perception so that they don’t disturb us.

The whole television programme was about the possibility of life elsewhere in the universe (and was actually subtitled “Are We Alone?”), culminating in a discussion about intelligent alien life, so to dismiss the possibility of alien intelligent life on the basis of ‘no self-replicating machines’ without giving his reasons seems a bit lax.
Maybe he thought that the audience for such a programme wouldn’t be interested in arguments that were made in order to be dismissed, or maybe he just ran out of time (Time that could have been found, may I suggest, by cutting the silly sequence in which school children lined up with coloured lanterns to depict, very badly, the Hertzsprung-Russell diagram perhaps. Anyone who could make sense of that sequence probably already knew what the Hertzsprung-Russell diagram was).


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Would you be eternally grateful if you lived for ever?

I’ve just read a review of the book Sapiens: A Brief History of Humankind by Yuval Noah Harari. I’ve also read a short extract from the book in a newspaper and I’ve listened to a few articles about the book on the radio. I haven’t got time to read the actual book itself though, as life is short and I’m a slow reader (This is relevant to the point of this post, so keep reading).
According to the review of the book (in the Guardian, by Galen Strawson), Harari claims that ‘the leading project of the scientific revolution’ is the Gilgamesh Project: ‘to give humankind eternal life’ or ‘amortality’. I’ve never heard of the Gilgamesh Project myself, however I do know that Gilgamesh was a heroic character from a Mesopotamian epic poem who sought to destroy death (although an internet search for Gilgamesh would have you believe that the name is chiefly associated with a fancy restaurant in Camden, London).
Amortality, if you were wondering, is a sort of immortality-lite. Its definition is that you keep living until you die as the result of extreme violence, catastrophic accident or such-like. This is unlike full-blown immortality with which you get to live for ever no matter what.
Harari apparently isn’t certain of the merits of amortality, and doubts that it would bring much satisfaction to people were they to achieve it.

I think he’s probably correct.
Amortality has a certain superficial appeal – for instance it would give me enough time to actually read Harari’s book rather than simply dipping into reviews and articles about it – however here are a few points that need to be considered before judging it to be desirable.

I won’t spend any time here going into the potentially dire problems associated with actual immortality itself. Suffice to say that if you were burdened with eternal life you wouldn’t be eternally grateful for it. (For more on the down-side of eternal life click here.)

With amortality it’s possible to live more or less for ever as long as you avoid anything that’s going to kill you. This sounds great, as it implies that you could live for several hundreds of years or even thousands of years and then choose to die once you’d become bored with existence. The trouble is that I don’t think it would work quite like that in practice.
It’s hard to tell, because we’re not in the state of amortality ourselves, and if we were I’m sure that our outlooks on the subject would shift somewhat, but I think that in an amortal state, in which death is not necessarily inevitable, the status of death would change radically.
Look at it this way – we mere mortals know of the inevitability of death, so for us it’s mostly a matter of when it comes rather than if it comes. We have to confront the subject of death with a degree of grudging acceptance. If however we were amortal and could in theory avoid death simply by being extremely careful, then death would possibly become a totally different problem – it may even become a worse spectre than it is to we mortals. Death for amortals would cut off their access to immortality. True, people probably wouldn’t opt for true immortality if they really thought about it, but once you’ve got the option it’s probably a hard thing to throw away despite its manifold drawbacks. If you were an amortal, death could be a problem because you’d have so much to lose – all those years stretching into the infinite future. On top of this, the fact that death wouldn’t be inevitable would mean that people may not develop a sense of acceptance about it, so it would be a real threat in a different way than it is for us for whom it’s the natural end point of a finite span.

I’m assuming that if people managed to become amortal it would be due to a mixture of medical and technological innovations. Disease would be conquered and injury and wear-and-tear would be remedied by the use of replacement parts or by some form of bio-technical intervention.
If amortality didn’t include the fixing of injuries (other than truly fatal ones of course, such as those caused by falling into a mincing machine) life would eventually become unbearable due to accumulated handicaps, either large or small. Imagine if you lost an arm in an accident one day, then a hundred years later you lost an eye, then some time after that a leg. Then the other eye, the other arm, the other leg. Everyone would be queueing up next to the mincing machine. In such a case the state of amortality would only exist in theory rather than in practice – lifespan would be self-limiting due to assisted suicide.
It’s easy to imagine that people who lived in such a state would be so pathologically risk averse that there lives would be unbearable.

A world in which all injuries are repairable would be preferable, but that inevitably brings its own problems unfortunately, although perhaps less onerous ones. One of these is the downgrading of non-fatal risk. If all risk of injury (other than fatal injury) becomes nonexistent due to the ease of neutralising the consequences then people’s feelings about risk and aggression would possibly change. There’d be no thrill in minor acts of risk such as driving a car too fast or skiing. Obviously. in our world skiing and driving too fast bring with them the possibility of death, however in the world of the amortals I suspect that great efforts would be made to protect the individual from this fate while conducting those activities, such as by the introduction of bizarre headgear that is guaranteed to protect the brain from terminal crushing.
Any high risk activity in which there was the slightest chance of death despite any interventions or safeguards (such as bizarre headgear) would not be indulged in at all.

If we were to acquire an amortal lifestyle the chances are that we’d need our brains to be rewired somewhat in order for us to cope with the consequences of having a potentially very long lifespan – but then with a rewired brain we probably wouldn’t appreciate the fact that we’d acquired such a lengthy existence. So there’d possibly be little point in the whole exercise in the first place.
We only want an extended lifespan because of the brains that we’ve got now, not because of the brains that we’d have then.

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Urban astronomy – seeing stars from cities

It’s usually assumed that attempting to study the stars from urban environments is a waste of time.

This isn’t true, as proved by the discovery of  supernova 2014J last month.

News coverage of the discovery of the supernova here in Britain  concentrated on the fact that it was discovered purely by chance by a lecturer (Dr. Steve Fossey) and a group of students from University College, London. Dr Fossey was demonstrating how to use a particular telescope at the college’s observatory and chose the galaxy M82, in which the supernova lies, purely because of the thickening cloud cover that was obliterating other areas of the sky. What struck me most about this news was that the observatory is in Mill Hill, north London. I drive past it quite often. It is right beside a huge trunk road and is marooned in the the vast expanse of London’s suburban sprawl. Every time I go past it I think how sad it is that such a nice observatory should find itself enveloped in the glare of city lights, making useful observations well nigh impossible – or so I thought until the discovery of the supernova. I’ll look at the place differently in future.

A quick look at the observatory’s web page  shows me that the observatory conducts public tours every few weeks during the autumn and winter, and that, surprise surprise, they are now fully booked for the rest of this season.

Supernovae are perhaps the most distant celestial objects that you’re ever likely to see. Fortunately for the urban astronomer one of the most interesting objects to look at in the night sky is the closest celestial object – the moon. The moon is a little less exotic than a supernova, granted, but due to its proximity to the earth it makes fascinating viewing.

From my base in north London – just a few miles from the observatory that discovered supernova 2014J – a person would be hard pushed to make out even the stars of Orion, the glare in the sky is so bad. Despite this,  it’s well worth training a telescope on the moon. The moon is bright enough to shine through almost any amount of metropolitan fug (in fact the dimming of the moon by the urban air may enhance viewing, as the light from the moon on a clear night in the countryside can be almost too bright when viewed through a telescope). What’s more, the moon changes its appearance every single night as it goes through its phases, with different craters and other features standing out on different nights. Buy yourself a decent lunar atlas and start exploring (I use the Cambridge Photographic Moon Atlas myself).

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