Darwinian theory is still able to explain natural reality

The lesson that nature continually gives us, about how very complex adaptations can be produced without any “intelligent design”, purpose or ability to set a goal, thanks to the pure effect of the composition of random genotypes and subsequent Darwinian selection, is one of those that must be remembered every time, because its mechanism is capable of producing objects so perfect that they necessarily seem to be the work of a superior will or being. An example will serve to fully illustrate what I mean. There is a South African plant, a variety of daisy with small, orange flowers called Widespread gory, which has a very accurate reproduction of the female of certain flies on its petals. Through this structure, attracts male insects, which, in repeated attempts to mate with this bait, end up covering themselves with pollen, which is transported from plant to plant during the insect’s repeated attempts to perpetuate its offspring. In the eyes of a diptera, the three-dimensional reproduction of the female is perfect, complete with hairy protuberances, wings closed in repose and white reflections, and from a distance it can deceive even a human being, because these simulacra are mostly scattered in random positions on the corolla of the flower, realistically suggesting the presence of two-three insects intent on feeding.

Now, there are two interesting questions that can be asked, both of which have found an elegant answer in a recently published work. The first, for anyone unfamiliar with natural evolution, is about how such a perfect simulacrum was produced, from a plant that cannot control its work nor can it have any intention. The second, of more specialized interest, is how did such an adaptation emerge in a relatively short timegiven that, compared to most living organisms, the group of plants that includes these plants is very young in evolutionary terms, with an age between 1.5 and 2 million years and considering that the oldest species of this group do not have the fake flies on the petals.

The answer to the first question comes from the comparative analysis of the species within the group to which it belongs Widespread gory. By comparing the different species in the evolutionary tree of this plant, the researchers were able to identify a precise timeline of gradual adaptations leading up to the fake flies: first spots of color appeared, then the positioning of these spots gradually became less symmetrical and their shape more similar to an insect, finally hairs and bumps appeared to perfect the simulacrum obtained. Each of these variations, by itself, incrementally increases the attractiveness of the flower for flies: first of all the dark spots, which could also correspond to food sources (remember that many flies are attracted to darker colours), then the disappearance of the symmetry, which reinforces both the food and sexual signals of dark spots, and finally the further refinements, which definitely point towards the stronger and more specific sexual signal, are all variations with an additive effect, which means that it was not necessary to develop the perfect structure we see today in one go, since each intermediate step already conferred a selective advantage on plants displaying the corresponding traits. But, and here we come to the second question, how was it possible to develop all this through random mutations, in an evolutionarily very short time such as that of the history of this group of plants?

The point is that the whole artifice depends on the expression of three groups of genes, which already existed in the plant because they were essential for other functions. In other words, no new, dedicated genes have evolved: to obtain the false flies, genes already available to the plant were reused, in a different way than usual. The first group of genes, relating to color, is involved in the transport of iron: these immobilize the metal in specific areas of the petals, varying its color from yellow-orange to a dark color of the metallic blue-green type, much more similar to that of a fly. The second group of genes consists of DNA sequences that would normally control flowering, i.e. the expression of other genes necessary for this process: these have been recruited to ensure that the first group is “turned on” in random areas of the petals , thus giving a non-symmetrical arrangement to the dark colored spots and controlling their shape in the smallest details. Finally, the third group of genes is normally active in the formation of root hairs: this controls the arrangement of hairs and humps in the fly simulacrum built by the plant.

As you see, evolution has acted in this case not by creating new genetic inventions, but by controlling the use of pre-existing genetic material in a different way; this allows us to explain the evolutionary speed of the process of adaptation of the plant to its pollinator, and is a perfect example of that “bricolage” often referred to to explain the appearance of complex structures starting from the combination of pre-existing elements, destined for other functions. I don’t know when and if we will end up finding confirmations to the wonderful heuristic revealed by Darwin, perhaps identifying something that is inexplicable or contradictory with the mechanism that he illustrated; to this day, however, the innumerable series of magnificent examples of its validity, to which this last is added, constitutes an intellectual spectacle which has few equals in the edifice of human knowledge.