What drives the incredible diversity of life on Earth? How can random changes lead to such complex and well-adapted organisms?
According to Daniel Dennett, a fascinating algorithmic process transforms simple genetic changes into the rich tapestry of life we see today. In his book Darwin’s Dangerous Idea, he contends that the evolutionary algorithm is a repeated process of two steps over a long period of time.
Read on to learn how the two steps of evolution—random mutations and natural selection—work together to create the remarkable adaptations we observe in nature.
The 2 Steps of Evolution
Dennett writes that one of the most controversial Darwinian principles is that the natural world emerged not through intentional design but through an algorithmic process. This evolutionary algorithm, like all algorithmic processes, is a set of rules that follow scientific or mathematical principles. One example of an algorithmic process that occurs in nature is how a river shapes a landscape. Imagine a vast, flat plain with a river running through it. The river doesn’t have a “mind” or a “plan,” but it follows simple “rules” or steps based on physics: As the water flows downhill, parts of the river where the water runs fast will erode more soil, and parts where the water flows slowly will deposit sediment. These simple rules, acting over thousands of years, can transform a landscape into something complex and beautiful, like the Grand Canyon.
Dennett argues that evolution likewise unfolds according to an algorithmic process. The steps of evolution, when repeated for millions of years, produce the diversity and complexity of life we see around us—without needing a conscious designer to guide the process.
| Haldane’s Dilemma and the Rate of Beneficial Mutations Haldane’s dilemma, proposed in 1957 by British geneticist J.B.S. Haldane, presents a significant challenge to the view of evolution as a simple algorithmic process. At its core, the dilemma points out that the rate of beneficial genetic mutations appears to be too slow to account for the observed pace of evolutionary change in nature. Haldane calculated that the number of deaths required to fix a single detrimental gene in a population would be about 30 times the number of individuals in a generation, suggesting that each beneficial mutation would take an extremely long time to occur. Given the limited length of Earth’s history, Haldane’s calculations imply that there hasn’t been enough time for all the observed evolutionary changes to occur through this process alone. This challenges the idea that evolution proceeds solely through a simple, step-by-step algorithmic process of random mutation and natural selection. Haldane’s dilemma may suggest that our understanding of how evolution works is incomplete, that the rate of beneficial mutations is much higher than Haldane calculated, or that there are other mechanisms accelerating evolutionary change. |
Next, we’ll explore the two key steps of evolution: random mutation and natural selection.
Step #1: Random Mutation
Random mutation, writes Dennett, is a series of unplanned, undirected changes in genetic material. These mutations occur spontaneously during DNA replication or as a result of environmental factors like radiation or chemical exposure. Random mutations can lead to changes in the physical characteristics (known as the phenotype) of an organism, such as differences in appearance, structure, or the function of body parts.
According to Dennett, these changes are not guided by any intelligence or purpose; instead, they happen purely by chance.
Most Mutations Are Insignificant or Harmful
Dennett notes that most mutations don’t lead to improved features or enhanced survival capabilities. In fact, he writes, the vast majority of mutations either have no discernible impact at all or tend to corrupt or degrade features rather than improve them—resulting in malfunctions or abnormalities that can be detrimental to an organism’s survival chances. Dennett emphasizes that only a very small percentage of mutations result in beneficial changes that enhance an organism’s genetic fitness for survival and reproduction and therefore get passed on.
Step #2: Natural Selection
Dennett writes that the second step of the evolutionary algorithm is natural selection. Organisms with beneficial mutations have an increased chance of surviving long enough to reproduce and pass those same advantageous traits onto their offspring. Over generations, these beneficial traits become more common within the population.
The Role of Environmental Pressure
According to Dennett, the environment in which organisms live largely determines which mutations are beneficial (and thus more likely to get passed on) and which aren’t. This is because different environments present different challenges and opportunities with respect to climate, food availability, predators, and competition for resources. Organisms with mutations that happen to be advantageous in their specific environment are more likely to survive and reproduce.
For example, imagine a population of wild, brown rabbits that evolves a mutation causing their fur to turn white in the winter. If these rabbits live in an area with snowy winters, this mutation will help them blend in during those months. Because it helps them survive, the mutation will be passed down to future generations. However, if this mutation appeared in a population of rabbits from a region where it doesn’t snow in the winter, it would not afford them the same survival advantage. Instead, it would make them more visible to predators during winter months and thus less likely to survive and pass the mutation on to subsequent generations.
