The evolution of horses has fascinated us for a long time – perhaps because horses contributed so importantly and in so many ways to our societies for several millennia, but also because many of us still have relationships with horses. We know that to understand an animal better we need to know where it came from and what it came from.
The evidence for horse evolution has been the most illustrated evolutionary story in the history of school and university textbooks, and museum display. It was the first popularised evolutionary series.
The horse has also played a central role in the development of evolutionary science. How the evidence for horse evolution has been interpreted and explained over the last 150 years is an interesting case-study of science in our society. It illustrates how science grows knowledge and changes us and our communities, but also how we influence science and limit knowledge.
A post introducing evolution is required early in this blog because evolution is central to modern biology, including our understanding of horse physiology, behaviour and ecology.
In the minds of many, evolution and adaptation are the same but they are not. Evolution is simply biological – living and inherited – change through time. Evolution is a fact – populations and species do inherit changes through time. That evolution has occurred and continues to occur is indisputable. With simple tools and a keen eye, you and I can measure evolution as it occurs.
For example, when populations of fish are harvested in ways that consistently remove the largest fish subsequent generations reach sexual maturity faster and at smaller sizes. With more technical expertise we could measure rapid evolution in greater detail. For example, animal diseases have evolved and now infect people, like human immunodeficiency viruses – HIV – and fish become resistant to poisons.
More dramatic evolutionary changes over many millennia can be measured using modern comparative genetics and seen in the preserved remains of once living things – fossils.
Scientific debates about evolution are not about whether or not evolution occurred or occurs. The evidence for evolution is accepted. The scientific debates are about HOW evolution occurs or, for specific living things, WHAT caused their evolution.There are many mechanisms that cause evolution. Some are sudden and dramatic like the global catastrophe of a meteor impact or rapid climate change that cause extinction of species and populations. Some mechanisms will be more subtle and occur slowly, like the differences that emerge between two populations of the same species when they are prevented from exchanging members. Our goal is to try and understand how changes occur and what causes those changes.
In future posts under the category Evolution I will describe the evolution of horses and other Perissodactyla. I will investigate what is understood about how they evolved and what caused their evolution. I will examine how the accumulating evidence for horse evolution modified scientific thinking. Perhaps more interesting still, I will consider how scientific thought has been constrained by the interaction of that evidence with the expectations and prejudices of contemporary society. This will not just be a journey in science, but science in society.
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