Interesting stuff about the science of evolution and the natural world

Look away now.

A few years ago I created a flower meadow in my garden and I like to see what wildlife might make it their home. One very impressive beast which occasionally makes an appearance is the wasp spider (Argiope bruennichi). Every year I keep a close eye out for them and this year I’ve been lucky again after a few years’ absence.

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It was in a slightly hidden position on its web, and as I inched my camera forward through the grass it took fright. But luckily it scampered up the dry stems to a much more exposed position and I could get a clear view – very obliging of it.

I still have a slight arachnophobia, which has gradually faded over the years, but I’ve always found spiders very impressive beasts and this has to be one of the most striking you’re likely to find in the UK.

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New Whale

The Natural History Museum in London has reopened its main hall after closure for a makeover, and centre stage now goes to the blue whale skeleton, suspended high above the visitors, in a diving position.

I paid a visit on the first day and was very impressed. I’ll admit I was a little disappointed when they announced Dippy the dinosaur was to end its stay there, but the new resident of Hintze Hall dominates and fills the space even more effectively. It’s sheer bulk and central overhead position create a dramatic statement never before experienced in the museum’s main hall. My favourite viewing position is probably the balcony – here you get the closest view and can appreciate it’s true size, including the jawbone – the largest bone in the animal world.

The museum have chosen the name Hope for their new star exhibit (though I suspect the name won’t quite capture the public imagination in the same way as ‘Dippy’), and it symbolises the way we must look after the natural world which we live in and are part of. During the hunting era the blue whale came close to extinction, but since the ban in 1966 things are looking much brighter. The population is still small compared to what is was, but it seems to be rising every year.

The exhibits around the edges of Hinzte Hall have also been changed. There are ten bays on the ground floor – five have displays representing various stages in the history of evolution, and five have examples of current life.

A beautiful section of rock shows some highly colourful banded iron formations.

These were created over 2 billion years ago when the first photosynthetic organisms began to oxygenate the atmosphere. There was plenty of dissolved iron around at that time and so iron oxides were created – effectively the world rusted, and created some beautifully coloured rocks. Once all the free iron was used up such an event was never to happen again.

I think my favourite new exhibit is the cabinet of insects.

This is an all glass case with insects of various groups stuck onto glass panes, giving a wonderful impression that they are all flying up towards the roof.

Our Unique Responsibility

I thought I’d write a bit about some of my thoughts on conservation issues, with a particular emphasis on humans as part of the natural world, rather than the way we’re normally seen as something separate. There’s so often a distinction drawn between the natural world and the human world, but I personally think it’s more useful not to make the contrast, since it doesn’t really exist. I’ll also pose a few questions – ones which need answering for each of us to decide where our own thoughts lie.

Extinction is a perfectly natural thing. It’s happening all the time and it’s often one species that causes another to cease to be. One well studied example of this is the Great American Interchange. North and South America were not always joined together – the Isthmus of Panama only linked the two some 3 million years ago, and the previously separated ecosystems were able to mix together. Species migrated both north and south, and there were ultimately bound to be winners and losers – some extended their ranges whilst others became extinct.

Humans also cause extinctions. Homo sapiens – modern humans – evolved around 200,000 years ago in eastern Africa, and began to spread across the globe around 70,000 years ago. They were immediately successful, and proficient hunters – and so began the extinctions of the hunted. But is this to be viewed as a completely natural event? Personally, I don’t see a great deal of difference between this and other extinctions such as those when the Americas joined up, but fast forward a few years and perhaps things need to be viewed in a different light.

I see two major differences. One is the sheer scale of our impact. Not only do we hunt other species to extinction but we destroy vast areas of habitat for our own use, we kill for our own pleasure and we contaminate with chemicals that pollute or alter the world. Though I think these things could still be seen in a natural context – on an individual basis we are just driven by the universal desire to survive and reproduce. However, the other difference is the one that makes us unique. We are the only species to have a consciousness of ourselves and the impact we have on all that is around us. We are the only one to be able to look beyond our own immediate needs and develop a morality concerning the wider impact of our actions.

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So are we to blame, are we at fault? If our actions are simply driven by individual desires of survival in a naturally competitive world, but our collective actions have major negative effects, then surely not. The situation could be compared to evolution. Evolution is driven purely by an individual’s desire to reproduce and pass on its genes to the next generation. Consider a predator for example. It might evolve to run faster and faster to be able to catch its prey. In doing so it might become so successful that it causes the extinction of that prey species, and in turn causing it’s own demise due to lack of food. This sort of scenario happens all the time – evolution has no ability to foresee such problems, it only works on individuals, with the destiny of the species as a whole left to an uncontrollable fate. Humans have only very recently become aware of the problems we create, so should we be let off the hook as far as blame is concerned? Is it no surprise we struggle to deal with the issues when individually we still have to look after our own survival?

So what are we to do with our recently acquired awareness of the wider consequences of our actions – we have no other species to look to for guidance. Undoubtedly we have to make some changes. I think we can draw a distinction between two types of environmental preservation. There is that which looks after the world around us because we know that if we didn’t there would be negative consequences for ourselves. I guess we’re still talking about self preservation here, but one which is more forward looking. Then there is the idea that we should look after things simply because we feel it’s wrong to make other species extinct. Now we’re talking about true altruism, and that’s also something which is probably unique to humans. Altruism goes against the theory of evolution entirely. It either doesn’t exist in the non-human living world or it’s very rare. If an organism does do something to help another (and they very commonly do) then it only does so because it will get something in return (or to put it slightly more precisely, it’s genes will benefit).

One big question is – how much of our thinking about conservation should be driven by this altruism? To put it perhaps slightly more cynically or controversially, is it really quite so altruistic as we might think? If a huge amount of time, effort and money is spent on a specific project to preserve a particular species, how much of the motivation to do this is driven by the fact that we like the species, we find it impressive and we personally want it to carry on existing? Surely there is at least some degree of more self serving thinking going on here.

Take for example the current situation with the decline in bee populations. There’s quite rightly a great concern for what’s happening, but it is very much helped by the fact that there is a lot of warm feelings towards bees. But what about the poor old wasp? OK, it’s not in the same danger, but if it were, would there be as much attention paid. In evolutionary terms it’s very close to a bee, there’s really not much difference between them. Few people like a wasp, and I must admit, I’m as guilty as anyone – I don’t really want them around if I’m honest. But an beautiful hornet on the other hand – now there’s an impressive beast. There’s a lot of inconsistent thinking going on somewhere.

So what of the future? Can we stop even bigger problems arising? The issue really boils down to human overpopulation, bringing us back to that ever present individual desire to survive and reproduce, and this being at odds with the bigger picture. I liken it to economics. Individuals struggle hard to earn money, and borrow even more because it’s the only way to buy a house, but eventually the bigger system breaks down and the bubble bursts, and we have recession or depression. Individuals have to act in a certain way to get by, but that way causes downfall in the longer term – just like the predator running too fast. Surely something similar will happen with the human species. We’ve not got there yet – overpopulation has caused problems but nothing genuinely catastrophic. But it’s still marching on and who can predict the problems of the future.

It was reading about Malthusian thinking that led both Darwin and Wallace to come up with their theories of evolution by natural selection. Malthus wrote about the way human populations are kept in check by limits on the amount of food available and by disease. Our abilities to combat those limits mean that the population goes on growing. But one day will some kind of Malthusian disaster finally come home to roost? One thing we now know is that every species that exists becomes extinct eventually, and a similar fate will befall humans one day for certain. But when and how will it happen? Not for a long time I’m sure, but in the meantime we do need to look after all that is around us. And sorry, there do seem to be rather a lot of questions to answer.

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The Pinnacle of Evolution

Is there a pinnacle of evolution, and if so what might it be? Perhaps, since we’re all humans here, then any answer we might come up with is bound to have a certain bias to it, or at least, it’s just going to be an individual’s viewpoint. Even so, and bearing this in mind, how might we judge and rate a pinnacle of evolution? We humans can get very enthusiastic about finding ways to rank things and then decreeing what is the top dog, leaving the rest to pale in an inferior wake.

So, what means of judgement could be used and what might come out on top? Perhaps something that’s evolved to thrive in temperatures way above that of the usual boiling point of water is pretty amazing from a human standpoint, and ought to make the shortlist. Or maybe the organism that grows to the largest size should be deemed the best – that prize probably goes to the giant sequoia which can grow to about 2000 tonnes. But that’s just an individual organism, wouldn’t it be better to consider a whole species instead? We can do that by working out their biomass – the combined weight of all the individuals within a species – and the answer comes as a bit of a surprise. I’m sure many would think that humans would come out on top here, but it’s actually the humble little Antarctic krill, the staple diet of many a whale. These unassuming crustaceans only weigh about half a gram each, but the combined weight of their 800 trillion individuals adds up to more than any other species. That’s got to equate to success surely?

But why stop at species level – why not look to groups for evidence of evolutionary excellence? We’re going to have a problem about defining what constitutes a group, but that aside, the beetles are going to fare pretty well here. Out of around 1.5 million species of organism currently known, about 400,000 of them are beetles (plus about 3,500 new species are described every year), so they must be doing something right.

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Then, of course, we could look to excellence at a particular feat – some things have clearly evolved features that surely put their ancestors in the shade. But again, what criteria to choose? Flight is a pretty amazing evolutionary achievement, so the prize could go jointly to bats, birds and insects, though perhaps we ought to choose the best flyer amongst them – would that be the fastest, highest, most maneuverable or the long distance record holder?

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Of course there are countless achievements we could pick on, but in our human conceit we’re going to have a natural tendency to keep on returning to brain-power as the natural one to choose over all others. But why should this be? True, the use of our brains probably means we have been able to thrive in more parts of the globe than any other single species, but by all other means of judgement we are inferior to at least some other life forms, and in most areas, vastly inferior.

So the point I’m leading up to, is that making any assessment on evolutionary achievement is arbitrary, subjective and unscientific. It’s easily possible to come up with a thousand different answers depending on how we choose to make a judgement.

But there’s also a more important fundamental issue here. The very idea that evolution has been leading to some kind of pinnacle – or leading anywhere for that matter – is a flawed notion. Evolution is just something that happens. It happens first due to random genetic variation by mutations, then through natural selection causing change in a whole population. This evolution will often have a tendency to create more complexity, but to rate this complexity as superior is purely a human judgement. Evolution doesn’t produce something better – it just produces something better fitted to the ever changing environment.

But of course, not everything needs to change to thrive. I’ll return to the first example I gave as a possible pinnacle of evolution. Something that’s evolved to live in temperatures above the normal boiling point of water seems pretty amazing from our perspective. But current research is suggesting that the very first life forms could have come about in just such an environment. Water in the deep oceans becomes heated in places where larva leaks through the thin crust. The high pressure down here keeps water liquid at higher temperatures than at the surface where it would boil, and it could have been in this type of environment that the first life forms came to be. Similar organisms still exist today in the form of archaea (previously classified as bacteria). So something that seems to us to be pretty extraordinary, perhaps needed no evolution at all to be what it is – it was, after all, the first thing to come into being. But equally fascinating is the fact that the archaea are still very much around today, and still forging a living in basically the same form. They have been evolving for exactly the same duration as a bat a beetle or a buttercup, and they are every bit as successful. In fact almost certainly more successful – after all, they’ve been around for about 4 billion years and they will still be around after those three have long gone.

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So, evolution might sometimes produce more complexity, or sometimes it might not. But to class one thing as better than something else in any way is just a biased, subjective and human-centred opinion. Evolution doesn’t work in that way – it has no agenda and it is not progressive. It cannot react, it can only be buffeted on the waves of happenstance, through the chance of mutation and natural selection. If success is defined by survival of an evolutionary line, then it seems that change is not necessarily a requirement. Sometimes simplicity is perfection, and perhaps sometimes that’s all that’s needed to survive.

Meet Sophie

There’s an exciting buzz at the Natural History Museum in London – a new dinosaur has gone on display, the first for a 100 years. It certainly is something quite special, partly because of it’s near perfect preservation, but also because it’s the genuine fossil on display rather than a cast, and it’s not behind glass – you really can get up close and personal.

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She’s a Stegosaurus and she’s been named Sophie, after the daughter of the main donor that made her acquisition possible, even though the museum scientists actually have no means of knowing if she really was female. But perhaps it’s appropriate – someone did comment that she looked very small and cute and maybe should be carrying a little designer handbag. In fact, the reason she’s small is that she died at quite a young age and was not at all fully grown, but at 5.6m (18 foot) she’s still impressive enough. Her full title is Stegosaurus stenops and she’s the best preserved of only six known fossils worldwide.

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Stegosaurus existed around 150 million years ago, right in the heart of the dinosaur era. This fossil was found in Wyoming in 2003 and it took 18 months to carefully dig it from the rock without damaging it. The museum acquired it a year ago and has since been carefully scanning and photographing it for research purposes. They hope to discover the reason it had the huge plates running along the back and tail – were they for display or heat control? Also it’s a bit of a mystery how an animal with such a small head and jaws managed to eat enough to grow so large.

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The museum has done a superb job with displaying Sophie on a beautifully sculpted plinth in the Earth Hall and you can view up close from ground level as well as from an overhead balcony. Exciting times at the museum – maybe more new exhibits are in the pipeline.

Birds are dinosaurs

This idea is nothing particularly new, but when I first heard it I thought it was stretching the truth a bit – birds may have evolved from dinosaurs though surely they became something quite different. But now I’ve discovered a little more, it seems the two share so much in common they do need to be considered as one.

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In fact the idea began to take form back in the early days of evolutionary thinking. In 1868 Thomas Huxley first showed the similarities between Archaeopteryx and dinosaurs and proposed a link between the two. It was widely accepted at the time, but fell out of favour in the early twentieth century. One reason was the presence of the wishbone in birds. The wishbone is formed by the fusion of the collar bones and at that time no fossil from the dinosaurs that birds were supposed to have evolved from showed any collar bones. More recently collar bones showed up in the fossil record so the theory was back on the table again.

Even more compelling evidence has come from the discovery of some dinosaur fossils that clearly had feathers. Feathers were originally thought to be the exclusive and defining feature of birds, so this discovery certainly put the cat amongst the pigeons so to speak. Or dare I say, the dinosaur amongst the pigeons. There is good evidence to suggest that some well known dinosaurs such as Tyrannosaurus and Velociraptor were feathered.

Anyway, all this has finally shown that birds evolved from dinosaurs, but what about the idea that they are dinosaurs. This becomes clearer when you look at the number of characteristics they share. Consider some bird features:

  • Possession of feathers
  • They walk on two legs
  • They have claws on their toes
  • Three toes point forwards and one back
  • Hollowed out bones form part of the respiratory system
  • They have a wishbone (exclusively amongst living animals)

All these features are also possessed by the group of dinosaurs they evolved from within. True, birds do have further exclusive adaptations, mainly associated with flying, but analysis of the large number of shared characteristics shows that they can be grouped with dinosaurs in modern classification. As I’ve mentioned in previous posts, all classification is arbitrary to some extent, but if we accept some method of grouping things then it does look like we have to merge these two together.

It’s also very illuminating to consider Archaeopteryx, that wonderfully iconic early bird.

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It clearly had feathered wings that were capable of flapping flight, albeit probably rather weakly, so it was undoubtedly a bird, assuming this is the trait we now use to define birds. And yet it retained many of the more primitive dinosaur features. Unlike today’s birds it had teeth, a bony tail (a modern bird’s tail is purely feathers), clawed fingers on it’s forelimbs, many back vertebrae, an unfused pelvis and unfused foot bones. It may have had wings, but bodily it was very much a dinosaur. So if Archaeopteryx was a flying dinosaur, and Archaeopteryx was also a bird, then birds are dinosaurs.

I guess it shouldn’t be such a difficult thing to accept. After all, we have no problem in calling bats flying mammals, so why not? And of course, it also means that dinosaurs never became extinct. Jurassic Park is in your garden right now.

OK, so this statement is completely wrong, but it serves to illustrate the false conclusion of thinking that we are descended from chimpanzees because we evolved from an ape of some sort and they are our closest living relative. But we evolved from them no more than they from us.

What we do share is a common ancestor which we both descended from, and this makes chimpanzees our closest living cousins in species terms, but not our actual ancestors. Understanding common ancestors is vital to understanding evolution and classification, so lets go back in time to trace our little corner of the tree of life.

DNA analysis has shown that the ancestor linking us with chimps existed about six million years ago, and other evidence suggests it was certain to have lived in Africa. No fossil has been found that can be definitely attributed to it, but there are a few contenders. So, since we have no proper name let’s just call it ape A. But what did it look like? It would have been fairly close in appearance to a chimpanzee and it would have walked on four legs (using knuckle walking similar to chimps and gorillas), lived in the forest and been an excellent tree climber.

Around this time the climate began to cool a little and become dryer, meaning the forest in Africa began to thin out and in places open plain took over. This may have caused the population of ape A to become split into two, and therefore each group pursued it’s own independent evolutionary path. One group remained in the forest and so there were few external pressures for it to change – it would eventually evolve into chimpanzees. The other group must have come under some environmental pressure to cause it to change. This may have been a further thinning of the forest it was living in, but for whatever reason, it gradually evolved to become more adapted to living in the plains rather than the forest. This branch eventually became modern humans.

So ape A is the common ancestor we share with chimpanzees and makes them our closest living cousin within the animal world. It also means that the chimpanzee’s closest cousin is us, rather than any other ape. We have both had the same amount of time to evolve since ape A existed, but the reason we look so dissimilar is due to the different path that the environment led us to take – we took to the plains and became hunter gatherers instead of staying in the forests.

The next nearest living relative to us (and chimpanzees) is the gorilla and we need to go back 7 million years from present to find the ancestor we all share – call it ape B. Again it would have lived in the African forest and there would have been a split in the population somehow, one line leading to gorillas and the other to ape A, and subsequently to chimpanzees and us.

Going back even further, about 18 million years from present, we come across the common ancestor to all the great apes. Great apes comprise gibbons, orang utans, gorillas, chimpanzees and humans. They are a separate group from monkeys and the key difference is that apes have no tail whereas all monkeys do (though in a few it is almost reduced to nothing). This is a good illustration of how common ancestors are so useful in defining evolutionary paths and modern classification. If apes are defined as separate from monkeys due to their lack of tail (although it’s actually slightly more complicated than that), then this could be traced back to the one single species that lacked a tail and is ancestor to all subsequent apes.

All major groupings will have a single common ancestor at some point. So for example the first mammal species I talked about in a previous post would have had mammary glands, three bones in the ear, warm blood and fur – and this is why all mammals possess these and why we put them into a group separate from all other animals. As we go back in time there will be common ancestors to larger and larger groupings, until we reach that one first originator of all life with that one huge characteristic that all life shares – DNA.