Dogs own us with their eyes
Nothing in Biology Makes Sense except in the Light of Evolution is the title of a paper by Dr. Theodosius Dobzhansky written for The American Biology Teacher. It is not a particularly long paper nor is it highly technical. Rather it is a reaffirmation that evolutionary principles are the foundational basis for all of biology – from the interaction of molecules to the behavior of whole herds of wildebeest.
Simply put, evolution rules. There are many people who still want to treat evolution as “just a theory” in much the same way as we use in public discourse. In explaining some events, such as an ice cream cone falling to the ground, someone will say “I have a theory as to why that happened”. In fact, they have an explanation and it usually boils down to inattention by the person eating the ice cream cone.
Theories in science – the ones which last for long periods of
time – are much more than just a simple explanation. They are a framework into which all of the existing data fits. They allow us to make meaningful predictions and to test predictions against theory.
One of the hallmarks of good science is the facts always win. If facts are discovered which contradict a theory, then the theory is modified. If it can’t be modified in a way which will incorporate the new data, then the theory is the thing which goes. It is called a paradigm shift and major shifts are infrequent but do happen.
The theory of evolution by natural selection was just such a paradigm shift. When Charles Darwin outlined his thesis in On the Origins of Species, he broke with the common view that species had existed forever or at least since the Earth was created. His explanation of how evolution could occur through natural selection provided a mechanism for speciation.
Of course, no one at the time knew anything about DNA or genes or the genome or epigenetics or a whole bunch of molecular biology which ultimately manifests in life. It could be argued all of the wonders of living organisms would have been uncovered in due course without the push the theory of evolution provided but that is not how history has unfolded.
The essential principle behind evolution is life will adapt to changes in the environment, albeit over many generations. It is the generational shift which is critical. Evolution acts by making an individual more or less fit to produce the next generation. Well-adapted organisms reproduce and their genes get carried to the next generation. Those not well adapted get weeded out of the gene pool.
Some organisms, such as bacteria, have very short generational spans. Single celled creatures can produce a whole new generation every 20 minutes or so. This can result in rapid evolution particularly when it is combined with DNA able to mutate or adopt genes from surrounding species. Bacteria are constantly evolving, which is how we have ended up with super bugs resistant to many common antibiotics. They have been under evolutionary pressure brought about by a change in their environment – the introduction of an antibiotic – and only the ones which could deal with the drug survived to produce the next generation.
None of this requires the intervention of any other organism. Or perhaps a better way to put it is evolution occurs naturally because of interactions between an organism and everything else in its environment, including other organisms.
This has recently been demonstrated for our faithful friends, dogs. In a recent paper in the Proceedings of the National Academy Sciences, Julianne Kaminski and colleagues present a case for the evolution of facial muscle anatomy in dogs. Her work examines the facial muscle structure of dogs and compares it to their close relative the wolf. Dogs have evolved a muscle which allows them to open their eyes wider – to give us and others their puppy dog eyes.
Anyone who has ever owned a dog knows they have very expressive faces. They are able to give us a look which we interpret as sadness or longing. This is particularly true for puppies which can melt even the hardest of hearts with a single glance.
While the muscle involved is a very small one, it is a major evolutionary distinction between wolves and dogs. In wolves, the same region contains only a bundle of undifferentiated tissue. Wolves can’t produce the same expression.
It is likely the expressive eyebrows and puppy dog eyes of their earliest ancestors which facilitated the domestication of wild dogs in the first place. Over the course of the last 30,000+ years, we have bred dogs to enhance the trait but it was evolution which allowed them to succeed in the first place and become one of the dominant life forms on this planet.