Showing posts with label Alfred Russel Wallace. Show all posts
Showing posts with label Alfred Russel Wallace. Show all posts

Monday 15 March 2021

Distorted Darwin: common misconceptions about evolution and natural selection

A few months' ago, I discussed how disagreements with religious texts can lead the devout to disagree with key scientific theories; presumably this is a case of fundamentalists denying the fundamentals? Of all the areas of scientific research that cause issues today, it is evolutionary biology that generates the most opposition. This is interesting in so many ways, not least because the primary texts of the Abrahamic religions have little to say on the topic beyond the almost universal elements seen in creation myths, namely that one or more superior beings created all life on Earth and that He/They placed humanity at the zenith.

Thanks to opposition to the modern evolutionary synthesis, there is a plethora of misinformation, from material taken out of context to complete falsehoods, that is used to promote Creationist ideas rather than scientifically-gleaned knowledge. Even those with well-meaning intentions often make mistakes when condensing the complexity of the origin and history of life into easy-to-digest material. I've previously written about the concepts of evolutionary bushes rather than ladders, concurrent rather than consecutive radiation of sister species and speciation via punctuated equilibrium (i.e., the uneven pace of evolution) so here are a few other examples where the origin, implications and illustrations of natural selection has been distorted or overly simplified to the point of inaccuracy.

I've previously mentioned that Charles Darwin was the earliest discoverer - but only a decade or two ahead of Alfred Russel Wallace - of natural selection, and not as is often written, evolution per se. However, this is not completely accurate. Darwin's hypothesis was more complete than Wallace's, in the sense of being entirely scientific and therefore testable. Wallace on the other hand maintained there must have been divine intervention in the creation of our species, making us different from all other life forms.

In addition, there were several precursors who partially formulated ideas regarding natural selection, but who were unable to promote a consistent, evidence-based hypothesis to anywhere near the extent that Darwin achieved. For example, as early as 1831 the Scottish agriculturalist Patrick Matthew published some notes on what he termed 'new diverging ramifications of life' as he thought must occur after mass extinctions. Nevertheless, he failed to expand and fully explain his ideas, seemingly unaware of where they could lead. In this sense, he is a minor figure compared to the thorough research Darwin undertook to back up his hypothesis. 

Darwin appears to have been unaware of Matthew's ideas, although the same could not be said for Robert Chambers' (anonymous) 1844 publication Vestiges of the Natural History of Creation, which although highly speculative contained some kernels of truth about the mechanisms behind biological evolution. Just as Thomas Malthus' 1798 An Essay on the Principle of Population inspired Darwin, so the mid-nineteenth century contained other combinations of ideas and real-world inspiration that provided,an ideal background for the formulation of natural selection. In other words, the conditions were ready for those with the correct mindset to uncover the mechanism behind evolution. What Darwin did was to combine the inspiration with an immense amount of rigour, including examples taken from selective breeding.

Another frequently quoted fallacy is that evolution always maintains a single direction from earlier, simpler organisms to later, more complex ones. I've covered this before in discussions of the evolution of our own species, as many popular biology accounts seek parallels between technological progress and a central branch of animal evolution leading ever upwards until it produced us. 

Modern techniques such as genetic analysis and sophisticated examination of fossils - including scanning their internal cavities – has negated this appealing but incorrect idea. For example, mammals evolved around the same time as the dinosaurs (and over one hundred million years before flowering plants) while parasitic species often have a far more rudimentary structure than their ancestors. 

Despite this, we still see countless illustrations showing a clear-cut path from primordial organisms 'up' to Homo sapiens. No-one who has seen the cranial endocast of a dinosaur would consider it to be superior to even the least intelligent of mammals, although the later medium-sized carnivorous species were on the way to developing a bird-like brain-to-body mass ratio. Yet throughout the Jurassic and Cretaceous periods, dinosaurs filled most ecological niches at the expense of the mammals; you would be hard-pressed to state that the latter were the dominant type of land organism during the Mesozoic!

Research published last year shows that New Zealand's unique tuatara, the sole remaining member of the Rhynchocephalia, is a reptile that shares some genetic similarities to the Monotremata, the egg-laying mammalian species known as platypus and echidna. In addition, a report from the beginning of this year states that the ancestors of today's five monotreme species diverged from all other mammals 187 million years ago; therefore, they have spent approximately three times as long on their own evolutionary journey as they did when part of all the other mammalian lineages. As a result of retaining many ancestral features, the platypus genome is in some ways more like that of birds and reptiles rather than placental and marsupial mammals. But we still include them amongst the mammals rather than as a hybrid or separate class; both platypus and echidna have fur, are warm-blooded and produce milk (although with a unique delivery system!) This allows their inclusion in Mammalia; does this mean we arbitrarily allow certain traits and discard others?

Would it be fair to say that the boundaries we make between organisms are more for our convenience than the underlying reality? Are you happy to label birds as 'avian dinosaurs' and if not, why not? If they had feathers, nests and even underground burrows, some dinosaurs were clearly part of the way there; physiologically, it was teeth, bony tail, and a crocodilian-type brain that provided the differentiation from birds. Scans of fossils show that dinosaur hearts may have been more like birds than other reptiles, which along with the possible discovery of bird-like air sacs, means that they could have had something of the former's more active lifestyle. 

This doesn't confirm that they were warm-blooded: today there are eight species, including leatherback turtles, that are mesothermic and therefore lie between warm- and cold-blooded metabolisms. Eggshell analysis suggests that some of the theropod (carnivorous) dinosaurs could have been warm-blooded, but as dinosaurs existed for around 165 million years it may be that some evolved to be mesothermic and others to be endothermic (i.e., fully warm-blooded). In this respect then, some meat-eating dinosaurs especially may have had more in common with us mammals than they did with other reptiles such as lizards and snakes.

All this only goes to show that there is far more to life's rich pageant than the just-so stories still used to illustrate the history of life. Science communication to the public is fundamental to our society but it needs to present the awkward complexities of evolution via all the tortured pathways of natural selection if it is not to fall victim to those who prefer myths of the last few thousand years to the history of countless millennia, as revealed in the genes and rocks waiting for us to explore.


Tuesday 23 December 2014

Easy fixes: simple corrections of some popular scientific misconceptions

A few months' ago I finally saw the film 'Gravity', courtesy of a friend with a home theatre system. Amongst the numerous technical errors - many pointed out on Twitter by Neil deGrasse Tyson - was one that I hadn't seen mentioned. This was how rapidly Sandra Bullock's character acclimatised to the several space stations and spacecraft immediately after removing her EVA suit helmet. As far as I am aware, the former have nitrogen-oxygen atmospheres whilst the suits are oxygen-only, necessitating several hours of acclimatisation.

I may of course be wrong on this, and of course dramatic tension would be pretty much destroyed if such delays had to be woven into the plot, but it got me thinking that there are some huge fundamental errors propagated in non-scientific circles. Therefore my Christmas/Hanukkah/holiday season present is a very brief, easy -on-the-brain round-up of a few of the more obvious examples.

  1. The Earth is perfect sphere.
    Nope, technically I think the term is 'oblate spheroid'. Basically, a planet's spin squashes the mass so that the polar diameter is less than the equatorial diameter. Earth is only about 0.3% flatter in polar axis but if you look at a photograph of Saturn you can see a very obvious squashing.

  2. Continental drift is the same thing as plate-tectonics.
    As a child I often read that these two were interchangeable, but this is not so. The former is the hypothesis that landmasses have moved over time whilst the latter is the mechanism now accepted to account for this, with the Earth's crust floating over the liquid mantle in large segments or plates.

    Geologist Alfred Wegener suggested the former in 1912 but is was largely pooh-poohed until the latter was discovered by ocean floor spreading half a century later. As Carl Sagan often said, "extraordinary claims require extraordinary evidence".

  3. A local increase in cold, wet weather proves that global warming is a fallacy.
    Unfortunately, chaose theory shows that even the minutest of initial changes can cause major differences of outcome, hence weather forecasting being far from an exact science.

    However, there is another evidence for the validity of this theory, fossil fuel lobbyists and religious fundamentalists aside. I haven't read anything to verify this, but off the top of my head I would suggest that if the warm water that currently travels north-east across the Atlantic from the Gulf of Mexico (and prevents north-western Europe from having cold Canadian eastern seaboard winters), then glacial meltwater may divert this warm, denser seawater. And then the Isles of Scilly off the Cornish coast may face as frosty a winter as the UK mainland!

  4. Evolution and natural selection are the same thing.
    Despite Charles Darwin's On the Origin of Species having been published in 1859, this mistake is as popular as ever. Evolution is simply the notion that a population within a parent species can slowly differentiate to become a daughter species, but until Darwin and Alfred Russel Wallace independently arrived at natural selection, there really wasn't a hypothesis for the mechanism.

    This isn't to say that there weren't attempts to provide one, it's just that none of them fit the facts quite as well as the elegant simplicity of natural selection. Of course today's technology, from DNA analysis to CAT scans of fossils, provides a lot more evidence than was available in the mid-Nineteenth Century. Gregor Mendel's breeding programmes were the start of genetics research that led to the modern evolutionary synthesis that has natural selection at its core.

  5. And finally…freefall vs zero gravity.
    Even orbiting astronauts have been known to say that they are in zero gravity when they are most definitely not. The issue is due to the equivalence of gravity and acceleration, an idea which was worked on by luminaries such as Galileo, Newton and Einstein. If you find yourself in low Earth orbit - as all post-Apollo astronauts are - then clearly you are still bound by our planet's gravity.

    After all, the Moon is approximately 1800 times further away from the Earth than the International Space Station (ISS), but it is kept in orbit by the Earth's pull (okay, so there is the combined Earth-Moon gravitational field, but I'm keeping this simple). By falling around the Earth at a certain speed, objects such as the ISS maintain a freefalling trajectory: too slow and the orbit would decay, causing the station to spiral inwards to a fiery end, whilst too fast would cause it to fly off into deep space.

    You can experience freefall yourself via such delights as an out-of-control plummeting elevator or a trip in an arc-flying astronaut training aircraft A.K.A. 'Vomit Comet'. I'm not sure I'd recommend either! Confusingly, there's also microgravity and weightlessness, but as it is almost Christmas we'll save that for another day.
There are no doubt numerous other, equally fundamental errors out there, which only goes to show that we could do with much better science education in our schools and media. After all, no-one would make so many similar magnitude mistakes regarding the humanities, would they? Or, like the writer H.L. Mencken, would I be better off appreciating that "nobody ever went broke underestimating the intelligence of the (American) public"? I hope not!

Monday 27 August 2012

Ancestral claims: why has there been comparatively little research into human origins?

It has been said that we live in a golden age of dinosaur discoveries: from Liaoning Province in China to the Dakota Badlands, new species are being named on an almost monthly basis. But if there is a plethora of dinosaur palaeontologists why has there seemingly been so few scientists studying the origin of Homo sapiens? Surely deciphering the ancestry of mankind is one of the great challenges?

The image of hominins has certainly evolved over the past thirty years, even the naming changing in scientific circles (from the broader term hominid), although as the title of the 2003 BBC series' Walking With Cavemen showed, popular perception has been slow to adopt new research. As a child, I had an early 1970s plastic model kit of a Neanderthal Man. I seem to recall it bore more than a passing resemblance to the Morlocks from the 1960 film adaptation of H.G. Wells's The Time Machine, a far cry from the individuals portrayed in Walking With Cavemen and other, more recent, series. Yet this idea of a shambling, zombie-like creature is still to some extent prevalent. Why should this be, when there is now evidence for Neanderthal ritual and art? Are we simply afraid of finding yet more nails in the coffin of human uniqueness (apologies for the rusty metaphor)?

There are still clear elements of taboo to the subject: the humbling  notion of humans being but a 'monkey shaved' was also felt by early evolutionists, with even natural selection co-founder Alfred Russel Wallace believing humanity the product of divine fiat. Perhaps a sense of embarrassment (try watching zoo visitors as they observe apes) combined with Western religious thought has prevented the discipline becoming popular in the way the love of all things dinosaur has skyrocketed since the 1970s.

Then again, it still seems that people misunderstand evolution via natural selection, considering progress as via ladders rather than differentiating bushes. The 2004 discovery of yet another new hominin species, Sahelanthropus tchadensis, led the Christian Science Monitor to describe it as that hoary old misnomer the 'missing link'. This is despite three decades of popularising by the likes of Dawkins, Fortey, Jay Gould, etal, to dispel the notion. You only have to read archaeologist (note: not palaeontologist) Mark Roberts’ account of the seemingly shoestring Homo heidelbergensis excavations at Boxgrove in England to realise that hominin research has been attracting about one per cent of the news (and a zillionth of the funds) directed towards cutting-edge particle physics.

A primary cause for the dearth of public knowledge can be put down to the actual lack of direct fossil evidence. Although Neanderthal remains were the first actually recognised as belonging to a human ancestor, it took several decades after the initial 1829 discovery before the identification was scientifically confirmed. Into the Twentieth Century the lack of finds allowed such embarrassments as the poor-quality Piltdown fake to be taken at face value. It is easy to see at least one key reason why this should be: human ancestry carries so much emotional baggage that it took over forty years before British scientists saw the obvious, instead of following the patriotism and jingoism inspired by the finds.

As it is, the history of hominin palaeontology has been riddled with contention, serendipity, unfortunate accidents and amateur bungling. If anyone wants to disprove the myth of science as a sterile, laboratory-conditioned activity, this sphere provides key evidence par excellence (good to get a rhythm going). From Eugene Dubois hiding his Java Man (Homo erectus) remains for several decades early in the Twentieth Century to the disappearance of Peking Man (also Homo erectus) fossils during the Second World War - not to mention the grinding up of yet more erectus bones for Chinese traditional medicine - the fate of finds is enough to make a dedicated specialist weep.

In addition, the fact that humans and their ancestors primarily evolved in what are today remote African locations with limited infrastructure can only exacerbate the situation. The work can be tedious, physically arduous and rewards few and far between. Yet fossil remains are the backbone of the discipline (almost a pun there, if you really look for it). After all, an increase in the number of finds can also lead to a paradigm shift in understanding: in the last few years it has been possible to undermine the opinion given on the BBC documentary The making of Walking with Dinosaurs, first broadcast back in 2000, that we would never know the colour of any dinosaur, courtesy of feathered Chinese theropod fossils (try saying that three times fast).

However, the last few decades has seen an improvement in the number of finds as funding has been allocated and professional enthusiasm increased. The problem has been that rather than solidifying the story of our ancestral line the number of species has multiplied without aiding the overall picture; there are still plenty of dashed lines on the human family tree. This indeterminacy has meant that a consensus is hard to find. If you examine any two charts of human ancestry, the chances are that they won’t agree. In the face of limited evidence it seems relatively easy for palaeoanthropologists to promote their own theories as to which species are our direct ancestors. Human nature being what it is, the favoured species usually happen to be those discovered by the said promoter. Such behaviour led to a thirty-year rift between two of the key players, Richard Leakey and Donald Johanson, partially over the number of branches on the direct ancestral tree. If anyone thinks the days of feuding scientists as long past (consider for example the Nineteenth Century American dinosaur pioneers Cope and Marsh) this quarrel ought to set the record straight.

One area of research that has undoubtedly given a boost to the understanding of human origins is the ability to retrieve and read ancient DNA. That’s not to say that it has yet produced much in the way of definitive evidence, but it undoubtedly widens the knowledge that can be gained from a paucity of finds. A recent report suggested that Homo sapiens and Neanderthals did not after all interbreed but share a similar genome via common ancestry. This is a reversal of a previous report that in turn countered earlier genetic evidence...and so on.

The relatively recent demise of the Neanderthals has provoked some interesting theories that show how science can reflect the concerns of contemporary society, namely that the violent aspect our species may have been directly responsible. There is currently no firm evidence for deliberate genocide, with other likely culprits ranging from inability to adjust to climate change to a less flexible neural architecture (specifically, missing out on the 'Great Leap Forward' via imaginative cogitation). Recent texts have attempted to downplay innate human aggression but writers closer in time to the world wars and to the heyday of Freudianism, especially Australian anthropologist Raymond Dart and American author Robert Ardrey, had a major influence on the subject with their promotion of the 'killer ape' theory. From 1960 onwards the first serious, sustained research on wild chimpanzees by Jane Goodall inadvertently reinforced the notion of mankind as a predominantly violent species. Given such notions, it is perhaps little wonder that funding has been lacking.

The new century has so far seen something of an improvement, with a large increase in the number of popular books and television programmes reflecting and in turn further developing public interest. The controversy surrounding the nature of the Homo floresiensis finds of 2003 has proved fortuitous, with general news media at long last paying serious attention. The ball may have been started rolling by the Chalcolithic ice mummy Otzi, who was discovered in the Alps in 1991. A young upstart at a mere 5,300 years old, the incredible preservation of the man, his clothing and tools have helped bridge the gap in how we relate to our prehistoric ancestors.

So times they are a-changing. The Ancient Human Occupation of Britain project is a sustained, well-funded effort to examine the past 700,000 years of evidence in the United Kingdom using a plethora of cross-discipline techniques in addition to conventional archaeology and palaeontology. The use of advanced dating methods such as electron spin resonance and the ability to analyse ancient DNA suggest that even without new finds, hominin research in the near future will generate some surprises. All I can say is that it's about time, too!