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.

Hot, cold or in between: thermoregulation and public misunderstanding of science

I recently spotted an intriguing paleontology article concerning the 180 million year old fossil remains of an ichthyosaur, a marine reptile from the Early Jurassic. The beastie, belonging to the genus Stenopterygius,  is so well preserved that it shows coloration patterns (if not the colours themselves) on patches of scaleless skin, as well as a thick layer of insulating fat or blubber. What makes the latter so intriguing is that reptiles just aren't meant to have blubber. Then again, like some snakes and skinks today, ichthyosaurs must have given birth to live young. Thus the gap between reptiles and mammals surely grows ever smaller?

This conundrum touches on some interesting issues about the public's knowledge of science. Several times I've commented on what Richard Dawkins calls the "tyranny of the discontinuous mind", which is the way in which we use categorisation to make it easier to understand the world. It might seem that this is the very essence of some aspects of science, as in New Zealand physicist Ernest Rutherford's famously ungenerous quote that "Physics is the only real science. The rest are just stamp collecting." Indeed, examination of the life and work of many early botanists for example might appear to verify this statement. However, there needs to be an understanding that science requires a flexibility of mind set, a fundamental scientific process being the discarding of a pet theory in favour of a more accurate one.

I'm sure I've remarked countless times - again, echoing Professor Dawkins - that science is in this respect the antithesis of most religions, which set key ideas into stone and refuse to accept any challenges towards them. In the case of the blubber-filled Stenopterygius, it is still a reptile, albeit one that had many of the attributes of mammals. As for the latter, from our pre-school picture books onwards we tend to think of the main mammalian subclass, the placentals, but there are two smaller subclasses: the marsupials, such as the kangaroo; and the monotremes, for example the duck-billed platypus. It has been known since the 1880s that the platypus lays eggs rather than giving birth to live young, a characteristic it shares with the other four monotreme species alive today. In addition, their body temperature is five degrees Celsius lower than that of placental mammals, part of a suite of features presumably retained from their mammal-like reptile ancestors.

Even so, these traits do not justify the comment made by host Stephen Fry in a 2005 episode of the BBC TV quiz show QI, when he claimed that marsupials are not mammals! Richard Dawkins has frequently pointed out that it would be unacceptable to have a similar level of ignorance about the arts as there is on scientific matters, with this being a clear case in point as regards the cultured and erudite Mr Fry. Yet somehow, much of the general public has either a lack or a confusion concerning basic science. Indeed, only  last week I listened to a BBC Radio topical comedy show in which none of the panel members could work out why one face of the moon is always hidden from our view. Imagine the response if it had been a basic lack of knowledge in the arts and literature, for example if an Oxbridge science graduate had claimed that Jane Austen had written Hamlet!

Coming back to the ichthyosaur, one thing we may have learnt as a child is that some animals are warm-blooded and others cold-blooded. This may be useful as a starting point but it is an overly-simplistic and largely outmoded evaluation of the relevant biology; the use of such binary categorisation is of little use after primary school age. In fact, there is series of steps from endothermic homeotherms (encompassing most mammals and birds) to ectothermic poikilotherms (most species of fish, reptiles, amphibians and invertebrates), with the former metabolic feature having evidently developed from the latter.

Ichthyosaurs are likely to have had one of the intermediate metabolisms, as may have been the case for some species of dinosaurs, possibly the smaller, feathered, carnivorous theropods. Likewise, some tuna and shark species are known to be able to produce heat internally, but in 2015 researchers at the US National Marine Fisheries Service announced that five species of the opah fish were found to be whole-body endotherms. Clearly, the boundaries between us supposedly higher mammals and everything else is far less secure than we had previously believed.

At times, science terminology might appear as too abstruse, too removed from the everyday and of little practical use outside of a pub quiz, but then does being able to critique Shakespeare or Charles Dickens help to reduce climate change or create a cure for cancer? Of course we should strive to be fully-rounded individuals, but for too long STEM has been side-lined or stereotyped as too difficult or irrelevant when compared with the humanities.

Lack of understanding of the subtleties and gradations (as opposed to clearly defined boundaries) in science make it easy for anti-science critics to generate public support. Ironically, this criticism tends to take one of two clearly opposing forms: firstly, that science is mostly useless - as epitomised by the Ig Nobel Prize; and alternatively, that it leads to dangerous inventions, as per the tabloid scare-mongering around genetically modified organisms (GMOs) or 'Frankenfoods' as they are caricatured.

Being able to discern nuanced arguments such as the current understanding of animal thermoregulation is a useful tool for all of us. Whether it is giving the public a chance to vote in scientifically-related referendums or just arming them so as to avoid quack medicine, STEM journalism needs to improve beyond the lazy complacency that has allowed such phrases as 'warm-blooded', 'living fossil', 'ice age' and 'zero gravity' to be repeatedly misused. Only then will science be seen as the useful, relevant and above all a much more approachable discipline than it is currently deemed to be.