Overcrowing

Darwin searched for signs of how traits were handed down from one generation to the next and how they changed in the process. . . . .Although he could see signs that species were not eternal, he still didn’t know of any way a species could take on a new form. Lamarck had claimed that animals could change over its life time and pass on its acquired characteristics to its offspring, but there was little evidence that this actually happened. Darwin looked for a different explanation for how evolution could unfold.

He found it in a gloomy book about humanity’s inevitable sufferings. In 1798 Thomas Malthus, a country parson, has written “An Essay on the Principle of Population.” oll.libertyfund.org/title/malthus-an-essay-on-the-principle-of-population-vol-1-1826-6th-ed In it he pointed out that a country’s population, ifit is unchecked by starvation or sickness, can explode in a matter of years. In every couple raised four children, the population could easily double in 25 years, and from then on, it would keep doubling. It would rise not arithmetically - but by a factor or 3, 4, 5, and so on -- but geometrically -- by factor of 4, 8, and 16.

If a country’s population did explode this way, Malthus warned that there was no hope that its food supply could keep up. Clearing new land for farming of improving the yields of crops might produce a bigger hrvest, but it could only increase arithmetically, not gemoetrically. Unchecked population growth inevitably brought famine and misery. The only reason that humanity wasn’t already in perpetual famine was because its growth was continually checked by forces such as plagues, infanticide, and simply putting off marriage till middle age.

Malthus pointed out that the same forces of fertility and starvation that shaped the human race were also at work on animals and plants. It flies went unchecked in their maggot making the world would soon be knee-deep in them. Most flies (and most members of every species) must die without having any offspring.

In Malthus’s grim essay, Darwin found the engine that could push evolution forward. The fortunate few who got to reproduce themselves wouldn’t be determined purely by luck. . . . Page 34