Thomas Malthus and the Theory of the Principle of Population

Thomas Malthus is the man I believe to of most effected Darwin's theory of Natural Selection. Malthus' contribution to the scientific community was An Essay on the Principles of Population. Although his theory was based around human population growth it is a topic that also follows well with Darwin's Theory of Evolution. Malthus' theory was that the human population tended to expand more while the resources would stay relatively the same, leaving the population to be kept in check by the amount of resources available. This relates to many of the bullet points stated including:

• all organisms have the potential of reproducing exponentially
• what is preventing organisms from reproducing at their potential?
• resources are limited
• organisms with better access to resources will be more successful in their reproductive efforts
•  who gets better access to these limited resources?

Malthus was discussing how populations have the potential to grow but are limited by the resources that are available to them, i.e. limited food and water. He also believed that a lack of food and water created famine and a decrease in population, but only to those who had difficulty obtaining them. To the people who have resources readily available to them they are viewed as more desirable and are able to pass on there traits. It's like a competition between humans for resources not between two different species like previously assumed.

Darwin could not of developed his theory without the help of Malthus he even said:

"In October 1838, that is, fifteen months after I had begun my systematic inquiry, I happened to read for amusement Malthus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long- continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The results of this would be the formation of a new species. Here, then I had at last got a theory by which to work".

                                   -Charles Darwin, from his autobiography. (1876)

Darwin's basis for his entire theory was on the fact that traits are passed on and are changed by surroundings and a need for adaption. Which is what Malthus provides, explanation on why a human population grows and expands or withers and dies based on resources available.

Why it took Darwin so long to publish his work was because at the time it was extremely controversial and the church would not accept it, many still don't. But he feared that going against the status quo would result in threats or the fate Galileo suffered. And the result of his publication was many people ignored it and chose not to believe and but it is now out there and is widely accepted.

Sites 
http://members.optusnet.com.au/exponentialist/Malthus_Evolution.htm
http://www.ucmp.berkeley.edu/history/malthus.html