Some prints from my recent exhibition are now available to buy through Saatchi on-line.
The intelligent design movement is a branch of creationism which, although driven by religious convictions, claims to criticise evolutionary theory on scientific grounds. An unbiased assessment of the evidence apparently leads to the logical conclusion that some sort of intelligence must have created the complexity of the biological world. At first glance it certainly seems a fair conclusion to draw, even atheist messiah Richard Dawkins (in one of his most quote minable moments) describes biology as “the study of complicated things that give the appearance of having been designed for a purpose”. Perfection in nature is integral to this way of thinking, things appear designed not only because they are complicated but because they appear so good at what they do but there is a problem; imperfection in nature is very common indeed.
Darwin wrote “It would be impossible to name one of the higher animals in which some part or other is not in a rudimentary condition”. How do we explain the abundance of imperfection, partial adaptations and downright hindrances we see in the natural world? Suboptimal traits exist because evolution makes the most of what is already there; natural selection can only act on the traits present in a population. If a new niche becomes available an organism will fill it; where there are no monkeys, kangaroos may take to the trees; where there is little meat, bears may take to eating bamboo. In the absence of competitors a species which is, at first, only poorly suited to the new environment may still successfully exploit it until, gradually shaped by natural selection, its traits become more suited to its new existence. For this reason complex, specialised organisms that have undergone a significant change in environmental pressures tend to exhibit some of the clearest examples of vestigiality. Cave dwelling fish are one such example; they all derive from ancestors that lived in sunlight but now live in total darkness.
Eyes are useless without light but some cave fish species still have eyes; even if technically capable of function these eyes can be considered vestigial since they have no function in their current environment. Many cave fish have no eyes as would be expected but pertinently some species have non-functional relics of eyes under skin or without connecting nerves to the brain. We often think of transitional species in relation only to fossils but these species are clear transitional forms, existing in a state originally adapted for life in the light and now only partially adapted for life in the dark. An intriguing variation on this theme is the cave fish Phreatichthys andruzzii which develops eyes but then rapidly loses them. The basic process for eye formation hasn’t been overridden instead a new process for rapid eye degeneration ensures the cornea turns into skin whilst the lens disappears entirely. http://www.nrcresearchpress.com/doi/abs/10.1139/z01-084
Many pieces of evolutionary history can be observed through developmental processes in embryos. There is huge similarity in early embryonic forms amongst the vertebrates pointing toward a shared ancestor but far more compelling are the pathways that are traced during an individual’s development.
In this clip you can see the formation of a human face. It is difficult to believe that this otherwise wholly unnecessarily similarity, first to fish and then to primitive tetrapods, was designed from scratch by an honest God. The similarity is not merely one of superficial resemblance but is revealed throughout our bodies and in our genes. Take human ears, for example, they are very complex organs containing the smallest bone in the body. The origin of our ears can be traced through the fossil record to some of the earliest land animals, primitive amniotes called synapsids, who originally heard using their lower jaw as reptiles do today. A bone from the lower jaw migrated into the ear to become the hammer, or malleus, that we use to hear today. Current fossil evidence shows this transition in wonderful clarity and the truth of the matter is further revealed by the way our ears develop in the uterus. The tiny bone that enables us to hear begins as a piece of cartilage in our lower jaw.
In The Origin Darwin cites G. H. Lewes “Salamandra atra, which lives high up among the mountains, brings forth its young full-formed. This animal never lives in the water. Yet if we open a gravid female, we find tadpoles inside her with exquisitely feathered gills; and when placed in water they swim about like the tadpoles of the water-newt. Obviously this aquatic organisation has no reference to the future life of the animal, nor has it any adaptation to its embryonic condition; it has solely reference to ancestral adaptations, it repeats a phase in the development of its progenitors”.
Rick Perry’s recent comments about evolution put the subject back in the spotlight and that led me to this blog article about evolution in US politics.
The author states her opinion of what evolution is and what portion of that definition she is happy to accept: natural selection, she says, is “the process in which individual organisms’ adaptation to their environment selects the traits that will be more frequently passed on to successive generations. There is nothing unconvincing about natural selection.”
Whether or not the author understands natural selection the ‘part of evolution’ that she ‘doesn’t find very convincing’ is common descent. It is a popular belief among those who like to think there is a legitimate basis for denying evolution that natural selection is not only factual but an obvious truism that Darwin deserves little credit for observing and that in arriving at broader conclusions about the origins of biological diversity Darwin simply extrapolated. This, they think, is the difference between the theory and the facts of evolution. Well evolution is both fact and theory but common descent is verifiable fact; so strongly supported by geographical, geological, physiological, radiological and genetic evidence that there can be no question of it ever being challenged by any future evidence. That may sound like an outrageously bold claim, isn’t science always based on current knowledge and susceptible to change? Yes and no, there are some things so rigidly supported by other facts, numerous accepted hypotheses and deeply interconnected with other realms of science that new information can only refine or add to what is there not overturn it.
Natural selection is an observable reality but nonetheless it is more likely to be challenged than common descent. Selection was Darwin’s explanation for how common descent occurred; that we share a direct ancestor with chimpanzees cannot be credibly questioned, any more than the shape of the Earth can, but our understanding of how this divergence took place may itself evolve.
The well-known professor Michael Behe had this to say in the New York Times: “The word ‘evolution’ carries many associations. Usually it means common descent — the idea that all organisms living and dead are related by common ancestry. I have no quarrel with the idea of common descent”. This may not seem a surprising comment from a scientist but this particular scientist is possibly the most prominent individual in the intelligent design movement and having defined what the concept of evolution usually means he then says he has no quarrel with it. If he accepts common descent what does he disagree with? It appears to him that certain instances of complexity within cells are hard to explain through a gradual, step by step selection of random mutations i.e. natural selection. Strangely most of his fans miss the point that he believes humans have evolved, not only from ape ancestors but ultimately from a single cell and that the process took many millions of years. Similar creationist misunderstandings of scientists are common; palaeontologist Jun-Yuan Chen is quoted as saying “In China we can criticize Darwin, but not the government; in America you can criticize the government, but not Darwin.” So is Jun-Yuan Chen a creationist? No, he is very much an evolutionary biologist but that you may jump to that conclusion is maybe why scientists in America aren’t keen on hearing him criticize Darwin.
This growing political minefield has its roots in a misunderstanding of scripture as much as a misunderstanding of biology. Former president Jimmy Carter made his position clear; “There can be no incompatibility between Christian faith and proven facts concerning geology, biology, and astronomy” “There is no need to teach that stars can fall out of the sky and land on a flat Earth in order to defend our religious faith.” In 1912 Woodrow Wilson answered regarding his opinion on evolution; “of course like every other man of intelligence and education I do believe in organic evolution. It surprises me that at this late date such questions should be raised.” He would have been even more surprised to learn that after a full century of exponentially growing evidence and universal scientific acceptance such a question may still hold a bearing on the presidency.
Last week marked the UK release of ’Rise of the Planet of the Apes’ a film that envisages a future where apes rule the Earth. Humans are, of course, apes and so similar are we to other apes that chimps and bonobos actually have more in common with us than they do with gorillas or orang-utans.
Amongst apes we have several unique adaptations, chiefly affecting the size and structure of the brain and skeletal changes favouring bipedal movement over quadrupedal. Perhaps the most obvious visual difference between us and other apes is the amount of body hair; actually a very superficial difference. Humans are still covered in hair but it is much thinner and shorter. When cold or threatened we still exhibit an atavism from our recent evolutionary past; goosebumps should serve to puff out body hair, trap heat or make us appear larger to our enemies. The loss of hair is thought to relate to the evolution of big brains; a bigger and more active brain generates a lot of heat and that would’ve been a problem in the hot area that hominids emerged from, loss of body hair enabled efficient cooling whilst the persistence of head hair protected the brain from the heating rays of the sun.
With such minor differences between us and our ape cousins Hollywood has an ideal subject for an anthropomorphic sci-fi adventure but there is an altogether more important implication of the similarity; apes make ideal subjects for medical testing. There are obvious reasons why this is a double edged sword; the more like us a non-human animal is, the better models they are for human disease but the more serious the ethical ramifications of conducting such research.
Last week a committee from the Institute of Medicine held a two day public hearing in Washington DC to examine whether there is still a need for invasive chimpanzee research. Outside of the USA Gabon is the only country where such research is still legal and there is a growing voice in the international community and from the USA itself that moving away from such practises is the best option ethically, financially and scientifically. A further meeting will be held in October with the IOM’s recommendations to be given by the end of the year. If all invasive experiments on apes were to be outlawed it would be probably be viewed by animal rights campaigners as the greatest step forward in the history of animal testing.
Any aspect of a ‘Goldilocks universe’ that is essential for our existence is not good proof for God since we could never exist in any other universe but that does not mean those universes cannot exist without us. I think a more compelling case for God can be made by focusing on the unessential curiosities of our universe; such as the sizes and relative distances of the sun and moon to Earth that facilitate the appearance of the corona during a solar eclipse. There is no reason why these two celestial bodies, with their vastly different sizes, should find themselves arranged about the earth in such a way that at times they appear exactly the same size but nonetheless that is the case. The result is that when the moon moves directly in front of our view of the sun it completely blocks the light from the sun and the delicate and most beautiful corona becomes visible. In this there is no proof for God either, of course, since it could be argued we only see it because it happens and wouldn’t miss it if had never happened but given the importance of both these bodies to human culture and the awe inspiring effect of witnessing an eclipse I consider it a nice example of the sort of phenomena that could be attributed to the footprint of a subtle and personal creator.
Darwin remarked that “several facts make me suspect that any sensitive nerve may be rendered sensitive to light, and likewise to those coarser vibrations of the air which produce sound.” How right he was.The heat sensitive pits of snakes evolved from chemical sensing ion channels http://wonderfulanimal.wordpress.com/2011/08/08/eye-to-the-past/ and another perfect example again confirms this idea; the evolution of infrared vision in vampire bats.
It has long been observed that vampire bats, which feed at night, are able to make straight for the best available areas of their prey. Being obligate blood feeders it is crucially important that they can find veins quickly and accurately and to achieve this they make use of an infrared sense via facial pits. How exactly this infrared sense worked had remained a mystery until recently.
A study* published last week in Nature looked at whether the same pathway used in the facial pits of snakes was associated with heat detection in vampire bats. It turns out that in bats the structures that allow them to see heat are unique adaptations of nerve cells that do normally detect heat but only at dangerous levels. The heat sensitive protein channel TRPV1 is normally activated by temperatures above 40°C, it is found in humans and involved in the burning sensation you feel when you touch something that is dangerously hot.
In vampire bats TRPV1 exists in two different forms, one about 5% shorter than the other and the distribution of the two isoforms is not random. The longer form is distributed around the body whilst the shorter form is found in high density in the trigeminal ganglia, a cluster of sensory neurones near the eyes, suggesting it may be involved in infrared detection. To test this scientists alternately expressed the two forms of TRPV1 in both human and frog cells in vitro and then measured their temperature sensitivity. The longer, more common, form was activated by temperatures above 40°C but the shorter form was triggered at 30°C. So vampire bats are able to see their prey in total darkness through a simple modification of a pre-existing sensory structure, this is another example of how flexible sensory structures are.
In the sixth chapter of his book Darwin addresses ‘Difficulties On The Theory’ and one of the most famous of the supposed difficulties is how evolution might form so complex and seemingly perfect an organ as the eye. In essence Darwin says that whilst it may seem absurd at first, that natural selection could create such interdependent complexity and apparent perfection, once you consider the individual steps from more primitive eyes to more derived forms it is in fact very easy to accept.
“How a nerve comes to be sensitive to light, hardly concerns us more than how life itself first originated; but I may remark that several facts make me suspect that any sensitive nerve may be rendered sensitive to light, and likewise to those coarser vibrations of the air which produce sound. In looking for the gradations by which an organ in any species has been perfected, we ought to look exclusively to its lineal ancestors; but this is scarcely ever possible, and we are forced in each case to look to species of the same group, that is to the collateral descendants from the same original parent-form, in order to see what gradations are possible”.
“In living bodies, variation will cause the slight alterations, generation will multiply them almost infinitely, and natural selection will pick out with unerring skill each improvement. Let this process go on for millions on millions of years; and during each year on millions of individuals of many kinds; and may we not believe that a living optical instrument might thus be formed as superior to one of glass as the works of the Creator are to those of man?”
What is true for the eye is also true for other complex sensory organs and a nice example of evolution at work can be found in a select group of reptiles. Three groups of snakes; boas, pythons and pit-vipers, are able to ‘see’ the body heat of their prey and can thereby hunt with greater accuracy and in total darkness. They do this through infrared sensitive facial pits. Being able to judge temperature from a distance also aids in predator avoidance and temperature regulation so there are many benefits and selective forces driving the evolution of the trait but how did the highly specialised sensory organs evolve? Well the cells in the pits of these snakes are not adapted from photoreceptor cells like those found in eyes but instead from nociceptor cells; nerve cells that detect chemical damage. Rather than being activated by photochemical transduction of infrared signals the pit organ is activated though radiant heating.*
So, the channel that is used by snakes to detect heat is an adapted form of another sensor that normally performs a very different role. Just as Darwin supposed, cells with one function can easily be sequestered to perform another. Also, as Darwin said, the comparison of species from the same group, “collateral descendants” as he called them, helps us understand how evolution of such organs progressed. In this case the pits of pit vipers are far more specialised and perfected than those of boas and pythons. Pits evolved independently in these different snakes and natural selection has so far managed to fine tune the pits of the pit vipers to a greater extent than those found in boas and pythons. In the absence of a multitude of certain lineal ancestors the existence of more primitive organ structures in similar taxa helps us understand how more specialised derived forms may emerge through gradual modifications of simpler, but still functional, structures.
Mostly when people think about evolution they think of a succession of small modifications over huge time scales. At any one point in time the biological picture should appear to be stationary, meaning evolution could never be observed first-hand and evolutionary relationships could only be deduced from genetic or fossil evidence. This is something that creationists cite when arguing that evolution can never be regarded as proven. There are, of course, many ways to establish truth outside of direct observation but nonetheless it is nice to see that sometimes we find evolution occurring within much smaller time scales.
The second largest family of lizards is that of the skinks. Being a very large family, over a thousand species, there is considerable variation in their appearance and habits but most are snake-like having a very short neck, long slender body and very short legs. Some species have no legs at all and it could be inferred that those which still posses tiny redundant limbs will eventually lose them entirely as natural selection strips them away. So skinks were already a good example of evolution acting now but last year scientists studying a species in Australia made a very interesting observation; individuals in one area reproduce through live birth whilst individuals in another area reproduce through egg-laying. Eggs don’t do well in very cold environments so live birth is a better option, this is such a strong selective pressure that evolution can occur quickly. Since the two populations are now distinct, in locality and in the pressures they face, mutations will occur independently in each population and accumulate until the two populations are no longer able to interbreed and can be considered separate species
To read the original article by Brian Handwerk in National Geographic click here
Many anti-evolutionists think the existence of so called ‘living fossils’ is proof that natural selection doesn’t occur or cannot lead to major changes over time. Needless to say it was actually Charles Darwin who coined the phrase and at the same time gave an immediate explanation of how apparent stasis might arise. “These anomalous forms may almost be called living fossils; they have endured to the present day, from having inhabited a confined area, and from having thus been exposed to less severe competition.”
Far from seeing them as a flaw in his theory Darwin writes about olm and other such species that he is “surprised that more wrecks of ancient life have not been preserved, owing to the less severe competition to which the inhabitants of these dark abodes will probably have been exposed.” Darwin’s explanation makes testable predictions about where and under what circumstances we should expect to find species that have changed little over time.
The olm is interesting from another perspective; being a cave-dweller it has no need of eyes since there is no light. The reduction or total loss of eyes is common in animals that inhabit total darkness and although olm still possesses eyes they are completely covered with skin. This clearly shows the animal to be in a transitional state, having descended from other salamanders that did have eyes; from a creationist point of view it must be difficult to explain why a species would be directly created with such functionless anatomy.
In Jules Verne’s novel, Twenty Thousand Leagues Under The Sea, Prof. Aronnax, states: “As long as I could deny the reality of the fact, I confined myself to a decided negative.”
I love how the character recognises his deliberate unwillingness to move from a preconceived perspective. In this case the professor’s reluctance to believe in a giant tusked whale was well founded but doubts are not always so. In July 1919 whalers off the coast of British Columbia captured a whale that may seem even less likely than the beast in the novel.
Many cetaceans reveal their four legged ancestry through internal vestiges of hind limbs but the discovery of a humpback whale with fully jointed legs protruding over four feet from it’s body is a remarkable thing. I think these bones are a concise and brilliant confirmation of evolution on a macro scale. The transition from small, hoofed, furry land mammal to enormous fish-like sea mammal is probably the most mind-blowing yet one of the best supported transitions of all.
Since I began with a line from Jules Verne’s novel I’d like to finish with another point that I feel is of relevance; The ‘Twenty Thousand Leagues’ of which the title refers to are not in depth, as often believed, but rather in distance travelled. This is better conveyed in the French that it was written. An English reader may be forgiven for thinking that the author believed the sea to be twenty thousand leagues deep and this highlights the problem of literality in translated materials, a problem that is further complicated when the source material is not only in another language but originally intended for a very different culture over 3000 years ago.