(Questions that were asked by myself along the way to giving lectures in genetics --circa 1992)

Theory of Evolution

  1. The number of organisms of any one type can increase in geometrical proportions. BUT
  2. The actual numbers of organisms of any one type remain constant over long periods.
  3. No two individuals of a type are identical, variation is characteristic, some of the variation is inherited


  1. Because more offspring produced than can be supported, there must be a struggle to survive.
  2. In this struggle, ones whose variations best adapt them to their surroundings, the fittest, survive.
  3. Because the variations are heritable, there will be a change in the proportions of the variations from generation to generation.


1st problem: What is fitness?

  • reproductive rates?
  • gene frequencies?

2nd problem: How do species arise?

  • what is a species?
  • no essential property, no natural kinds
  • reproductive isolation
  • share the same genotype
  • mechanism for a new species to arise?

A teleology is used to explain the organism by uncovering the needs, purposes, goals or functions of the whole system. We say that the genetic material contains information, expressed in a code. We attribute to transfer RNAs the power to recognize and discriminate amino-acid molecules from one another. We describe nucleases as making and correcting mistakes and errors, as editing and proofreading. Similarly , the specificity of an enzyme is described in the terms of its power to recognize substrates by their molecular shape.


Molecular Biology  - reductionist view

What we see at the molecular level is different than what we see at the macro-scale (individuals and communities)? At the level of DNA, how can the end be perceived by the genome?


Darwin at the time did not propose a mechanism as to how the survival of the fittest would work. Neo-Darwinists: took on the concept of the gene from Mendelian genetics, evolution was a change in gene frequencies. There was no detailed picture of what a gene was. From molecular biology we took on the concepts of DNA replication and molecular genetics as the explanation of evolution.

BUT in recent times:

  1. Selection? --- at level of gene, exon or species?
  1. Gene frequencies can be fixed without selection pressure.
  1. Periods of rapid evolution, followed by periods of stability.
  1. Genes are not necessarily independent or passive in the process of evolution.