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.
