By Don Lincoln, Ph.D., University of Notre Dame
The survival of the fittest keeps the individuals in any species that can later evolve and form new species. Environment and surrounding conditions change constantly, and once the fittest survive, they need to reproduce even fitter offspring to ensure survival. This is where evolution steps in.
Humans have a different kind of intelligence that has evolved only once throughout the whole history of life. Thus, we wrongly believe that humans are the most evolved species, and other creatures are at lower levels of evolution. The reality is that under any conditions, only the fittest survive. The definition of ‘fittest’ differs in each environment and condition, and so do the means for the survival of the fittest.
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Humans Are Not Cars
A misconception about evolution is that it works in the same way that human-made creatures, like cars, have evolved through the years. Comparing the 1885 Benz Motorwagen to the latest Mercedes products does not show how humans or other species evolve. Indeed, complexity in modern cars or other products is a prominent feature, but is it the same in evolution?
Complexity Through Evolution
Evolution is closely related to the survival of the fittest, and, surprisingly, it is not always the most complex that survives. Life dates back to 3.5 billion years ago, and there is even some ambiguous evidence that claims life formed shortly after the Earth did: 4.2 billion years ago.
Early life, called archaea, was simple: very simple organisms, single cells, with none of the structure found in more complicated forms of life. They were subcategorized as a kind of prokarya, cells with no nucleus. Bacteria also have no nucleus, but they are different forms of life.
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Eukaryotes were the first complicated forms of life, with a cell nucleus that contained DNA. Interestingly, eukaryotes still exist both as single-celled organisms and more complex forms, such as plants and animals. Plants are eukaryotes that contain chloroplasts, the powerhouse of plant cells, and animals are eukaryotes that contain mitochondria, the powerhouse of animal cells. Thus, more complex organisms can form through the same approach. Complexity through evolution can be drawn as a curve.
The Curve of Complexity
The plot for this curve has the complexity of organisms as the horizontal axis and how much of life on earth is of that amount of complexity on the vertical axis. The resulting curve would be an asymmetric bell curve with a short tail on the right for more complex organisms. On the left side, there is no tail. The reason is that creatures need a minimum complexity to live.
Stephen Jay Gould was one of the first people who brought about the topic. The curve has a big bump at low complexity and a long tail for more complexity. The simplest creatures at the left side are archaea and bacteria. Next, there are the eukarya, before the multicellular organisms like algae. They are followed by more complex species like fish, lizards, birds, mammals, and humans. The beginning of all this was the Cambrian explosion, about 540 million years ago.
Back then, there were no fish or mammals, but there were more complex forms of life, such as sponges. If survival of the fittest was bound only to complexity, the curve would have a bump at the more complex end, not the simpler one. However, the bump has remained on the left side with simple creatures.
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Do Only the Most Complex Survive?
The curve of complexity shows that, just like 500 million years ago, the dominant form of life is simple. Gould’s key point was that evolution does not lead to complexity; it leads to variety. The bacteria, the plants, the insects, and all the other simpler forms have evolved as well, but not into more complex things necessarily. They evolved to fit the new environments and survive.
The simple species outnumber humans significantly. For example, there are about 10 million single-celled species and probably over 1030 individual single-celled organisms. For example, the bacteria species ratio compared to humans is 10 million to one. The mass of these species equals the mass of plants found on earth or more than 1017 grams.
Beetles have also largely dominated the planet with over 300,000 to 400,000 species. Adding in the other insects would make the weight of insects on the planet 300 times the weight of humans.
Thus, our world is still full of single-celled and simple organisms that can survive in deepest seas, acid lakes, high temperatures or pressures, and many other environments that would immediately kill the sophisticated and complex species. The survival of the fittest makes sense in the light of the environment and the evolution required for that particular form of life.
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Common Questions about Survival of the Fittest
Survival of the fittest refers to the fact that the ‘fittest’ can survive in any environment, regardless of their complexity. For example, many complex creatures would immediately die in conditions that many bacteria live.
Neanderthals were our genetic ‘cousins’ who had a lot in common with humans but became extinct long ago. Humans more easily adapted to the changes of the environment, and as survival of the fittest explains, they survived.
Yes. The phrase ‘survival of the fittest’ was first used by Charles Darwin to show the genetic flexibility in adapting to new conditions and, hence, surviving.
Yes. The survival of the fittest applies to all forms of life and all environments, including humans at different stages. Neanderthals were not the fittest and did not survive, but humans were among the surviving groups of animals.