Bare Bones Biology 018 – The Most Important Thing I Know About Evolution

Evolution is a change in a gene pool over time. That’s what I said. But is that really a naïve, reductionist definition? Yes, it is. Certainly the evolution of one species is a change in its gene pool over time, but there really is no such thing as a change in one species over time. Everything in the living ecosystem changes together, and all things in one way or another influence other things.

The word that describes this is Co-evolution. Co-evolution is the way in which two or more species influence each other as conditions of their lives change over time.

For example, think of two gene pools that influence each other. Here is a mouse species. Above is a species of hawk. The hawk eats some of the mice; the remaining mice are able to pass their genes into their mouse gene pool. If the hawk is not able to catch mice, or if it catches so many that there aren’t enough left to eat, it will starve and will not be able to pass its genes on to the next generation of hawk gene pool. Over time the two species co-evolve to reach a balance, so that there normally are enough mice, not too many hawks, the mice are good at getting away, and the hawks are good at catching food.

But, in reality we must consider also that there is another species of hawk in the same space, and it eats mice in competition with the first hawk species. This competition also leads to co-evolution of the two species of hawk, along with the mice. There are other prey species for the two hawks and there are predators upon the hawks. There are also owls and other birds, and coyotes and cats, and deer. All of them are co-evolving. Their gene pools are in a constant process of change over time as a result of selection by all the other organisms. Furthermore, it is not only predator/prey relationships that influence this dance of life. There are parasites, availability of nesting sites, availability of water, climate requirements, and availability of organic food energy. And then the animals pass their feces and then they die and other organisms find their supply of organic food in the remains and provide fertilizer for more plants.

You could imagine the gene pools of all the species in an ecosystem as overlapping shapes, like Venn diagrams, drawn on a piece of paper, and then they move forward through time like a movie, changing the boundaries of the diagrams where their gene pools overlap and influence other species.

But there’s even more, when we consider that the mice and the deer and many of the insect species that are eaten by smaller birds, these all eat plants. In fact, the plants are the only source or organic food energy that keeps this whole enormous blue/green marble of an earth ecosystem alive. Organic energy from photosynthesis is the source of all life on earth, and there are many, many kinds of plants and other organisms on earth that can do photosynthesis. These are food for the life of the ecosystem, and the ability to get food is the biggest kind of selection over the life of any organism of any species.

All the mice and deer and the insects and other organisms that eat plants — all these can pass on their genes if they survive. But if there are too many of them — they will eat up all the food plants and then they will not be able to pass on their genes because they will starve. Then there won’t be enough mice and deer to feed the coyotes and hawks and insect-eating birds, and they will not be able to pass on their genes because of starving.

In other words, the concept of evolution is a simplistic human construct. The real purpose of evolution is to maintain the dance of balance among all the parts of life, so that none of the species destroys any of the other species and all together give life to the whole earth ecosystem that gives life to them. The fittest organism is not the one that disrupts this dance of balance.

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