This week very interesting news were released (except for really stubborn creationists), as Science published an article on the very first account of documented evolution happening by hybridization right in front of scientist’s eyes!
Due to their isolated conditions and high specialization, finches from Galapagos Islands have been the subject of numerous studies regarding evolution – starting with the original observations from Charles Darwin that led him to postulate his theory of evolution by natural selection.
What happened in this instance, was that a male finch from a different species (and a different island) arrived into one of the islands and successfully managed to mate with a female of one of the resident species and produce hybrid offspring. Such offspring was fertile and continued to breed within themselves, until about forty years later they conformed their own population of about 30 birds that now differ in both shape and behavior from other species on the island – and furthermore, do not mate outside of their own group. This means that in only three generations, a new independent species managed to emerge! Which challenges the traditional view of evolution as being an extremely slow and gradual process.
This led me to the point that I want to discuss today: misconceptions about evolution and how it shaped life in our planet.
One book that really changed the way I thought about evolution was Wonderful Life: The Burgess Shale and the Nature of History, written by Stephen Jay Gould.
Gould was a Biologist whose stellar work focused on Evolution. He also produced some of the most enthusiastic, easy to read and engaging science essays, articles and books on the matter; Wonderful Life is a representative example of his brilliancy at presenting interesting, fact-based ideas in an educational but also entertaining manner.
In this book, Gould presents some very innovative, intelligent and well-researched ideas that aim at bringing down some misconceptions that many of us have had implanted throughout education and popular culture. These are some of them:
Misconception #1: Evolution = Absolute progress
How many of us have seen the “march of progress”? That ubiquitous image showing monkey-like creatures walking in procession, progressively transforming into hominid shapes until finally reaching the triumphal Homo sapiens. Such image carries the pervasive connotation that evolution is a process of constant improvement; we can see plenty of it reflected in brand slogans, mottoes and often in inspirational advice:
However, we might be overseeing the fact that evolution, as directed by natural selection, is just a process that brings success to species in a relative way; in other words, the perceived advantages provided by the evolutionary process are only so under very specific, limited circumstances.
If we were to modify any of these circumstances, even a seemingly insignificant one, the species in question would probably not be successful anymore in such environment.
Gould opens up an even more provocative idea in this regard: he proposes an experiment in which we could “Rewind the tape of life”. This means, to start over again from the point of a barren Earth previous to the emergence of even the most primordial living beings, and let things develop and play all over again. Gould claims that if we were to do this while introducing minimal variations in the environmental circumstances, the resulting living organisms would be radically different from those we now know.
This is not only a thought experiment. Very interesting insights were obtained thanks to computer modelling, which boomed in the eighties regarding the development of different life simulation programs with different levels of complexity. People in the field referred to this as Artificial Life, which is a fascinating field on in its own, that opens many interesting scientific and philosophical questions, and will be the topic of a future post.
Still, I should note there is a counterargument of Gould’s proposed implications of “Rewinding the tape of life”. Daniel Dennett, another notable evolutionary biologist, affirms that some structures that are a product of evolution, like sensory organs, provide such a big advantage to their possessors over the other organisms and their environment that would invariably emerge at some point, which argues for evolution as a process with a defined direction.
Misconception #2: “The cone of increasing diversity”
Many of us tend to think that through evolution we have reached now the greatest diversity of existing life forms and organisms. This comes from a very old tradition of thinking, influenced by the way the emergence of species was depicted by early evolutionary scientists. A prime example of this are the "evolutionary trees" shown above, sketched by Ernst Haeckel, an eminent biologist from the 19th century.
The “cone of increasing diversity” is a traditional view of evolution as a progressive diversity that branches out from a single, primordial form. However, the fossil record shows that in very early times (the so called “Cambrian explosion” 541 million years ago, or maybe even before that) a greater diversity was present in terms of “body plans” (i.e. the way an animal body is put together). Such body plans were so radically different to the ones we know on this day and age that they cannot be classified under any of the Phyla* we know.
Still, out this initial wealth of designs only a few were selected and the rest were discarded, truncating their future development.
Hence, the diversity we observe now comes actually from variations of a limited repertoire of body plans (those which survived extinction); in other words, living organisms today represent only a few models (out of many more that existed millions of years ago) with a myriad of tiny variations that make each species unique.
*Note: Phyla is the plural of “Phylum”, and a Phylum is each one of the divisions of the different realms of nature; for example, within the animal kigdom, the Phylum Chordata represents cordate and vertebrate organisms (like us and most of the animals that are part of our diet).
Misconception #3: Evolution always goes from the simplest to the most complex.
Evolution does not have a completely defined, immutable direction, on the contrary, it acts according to the whims of environmental conditions at a certain time.
To understand this, we need to have a more global appreciation of life on Earth and pay closer attention to the mechanisms that result in the evolution of a species. Natural selection requires functionality that provides and advantage over the ever changing living conditions, which means that a complex organ that was useful but perhaps energy consuming, might not be required under certain conditions and actually burden the organism in a new environment.
In many cases, bodily structures have been simplified and specialized notably according to the environment an organism inhabits. One example of this are the legs of insects, which have derived from structures that were much more complex that disappeared through evolution.
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Image sources: All attributed above, except for the first one (bonus points to those geeky ones who recognize where I took it from! offer up your hearts!).