Evolution and Population
By Jim Strayer
In 1968, The Population Bomb by Paul Ehrlich was published. He predicted that hundreds of millions of people would starve to death soon if changes were not made. The levels of death that he predicted did not come true. On the other hand, about two hundred million people have died of starvation and hunger-related disease since 1968. When it was written, his detractors said that there would be no problem, that wonderful lives and a wonderful diet could be given to four or five billion people. That hasn't happened either. There is a vast uneven distribution of wealth in the world; even in wealthy nations like the United States.
The world population has grown from 1.6 billion in 1900, to about 6 billion in 2000. The world population is continuing to expand at about 80 million people a year.
Most of the population experts say that the earth can best support a population of about 2 billion people, and the United States about 145 million (at present the US has over 290 million). Industrial leaders, although admitting that there is unequal distribution, say that population is not a big problem.
What does all of this have to do with evolution? After all, evolution is small changes over long periods of time leading to the survival of those most able to produce young. It happens not in a few hundred years, but in thousands, if not millions of years.
There is a very important part to natural selection. It is that all species overproduce and that there must be some selective power to reduce the numbers. If this did not happen, there would be no natural selection.
As an example, a pair of cockroaches could produce 164 billion descendants after only seven months if there was no selection by natural processes. It is a good thing that humans take years to reach reproductive age, have a long gestation period, produce few young, and cannot produce often. Our evolutionary change is much slower than most species. The problem is that there is very little selection by natural causes in our species.
Natural selection can proceed at a faster rate if the species is isolated and has fewer members. The animals on the Galapagos Islands made noticeable changes in just a few million years after isolation. There were differences in humans isolated in China, Australia, and Europe after several thousand years.
The vast numbers of humans that have spread over the earth have almost removed the isolation factor from our species. We so dominate the earth and cause changes to happen in such a short time, that hundreds of species have become extinct and the rest are forced into an unreal world where the evolution of many species either advance rapidly because of pollution, or come to a complete stop because of extension.
What humans have done to bacteria, flies, domestic animals, and hundreds of other living things in just a few thousand years is not measurable on an evolutionary scale. The examples are everywhere: exotic plants and animals have been introduced into areas that they would not have migrated to on their own; chemicals are being produced that do not exist naturally on earth, and natural cycles are being disturbed.
Herbicides, pesticides, and fertilizers have all but destroyed soil in many places of the world. Water everywhere in the world is different from what it was just 100 years ago.
Evolution is a never-ending process. It has been continuing for about 4 billion years. Continents have moved, mountains have arisen and eroded away, magnetic fields have changed, asteroids have collided with earth, plants and animals have evolved, and humans have had an effect similar to a global disaster.
This is why the study of evolution is so important, and why so many scientists are involved in evolutionary research. Humans need to know where we came from and have some idea of where we may be going. But most importantly, we need to understand the impact that we are having on the evolution of life on earth. Nations and individuals tend to think in short terms. We owe the earth and our future generations some long-term planning on environmental issues that will have an evolutionary impact for stabilization.
It does seem impossible that we could reduce the population on earth to 2 billion people without a catastrophe. Obviously wars, famine, disease, and birth control have helped very little in population control when competing with human reproductive power.
Paul Ehrlich is still teaching about population and there are still many who disagree with him. Right or wrong, he gives a point of view that evolutionists must consider:
“The standard that biologists use and environmental scientists is very simple and that is you're overpopulated when you no longer can live on your interest, when you've got to live on your capital. And the three main forms of capital that we're getting rid of very, very rapidly at today's density and today's consumption patterns are deep rich agricultural soils, biodiversity, which is critical, and maybe the most short-term critical is our supplies of groundwater everywhere, which are being overdrafted. So, we are like the profligate child who has inherited a vast pile of resources, in this case from the planet, but every year we write a bigger check on it, but nobody bothers to look at what's happening to the balance, and that's the critical thing.“
About the Author
Jim Strayer has a Master of Science Degree from the University of Michigan. He worked in the biology teacher training program at Eastern Michigan University and he has twelve years of teaching experience at the high school level and twenty-two at the community college level. He is also the liaison for the National Center for Science Education representing central Florida.