The Great Merger: Modern Synthesis Evolution

If Darwin provided the mechanism for selection but lacked a mechanism for inheritance, and Mendel provided the rules for inheritance, then the combination of their work provides a complete framework for biology.

If we are analyzing the genetic diversity available for evolution within a specific group of interbreeding organisms, then we must look at the total collection of their genes. If this collection is treated as a single resource, then it is the gene pool.

If evolution is driven by shifts in genetic frequency, then factors that change those frequencies must be identified. If selection, drift, mutations, and migration (flow) all alter DNA patterns in a group, then they are the drivers; however, use and disuse is a rejected Lamarckian idea.

If small changes in allele frequencies (microevolution) accumulate over thousands of generations, then they eventually lead to the formation of new species and higher taxonomic groups. If these small steps lead to large results, then the two processes are linked.

If Darwin's theory was purely observational, then it needed a mathematical backbone to be scientifically rigorous. If the synthesis integrated population genetics and statistics, then it provided that essential mathematical basis.

If the synthesis is based on Mendelian genetics, then it follows that only changes in the germ-line (sperm and egg) can be inherited. If physical changes to the body (somatic) do not change the DNA of the offspring, then Lamarckism must be false.

If "adaptation" means a population becoming better suited to its environment, then the process must be non-random and favor survival. If genetic drift and mutation are random and gene flow is just movement, then only natural selection can consistently produce adaptive traits.

If the Biological Species Concept is used, then the ability to exchange genes is the defining factor. If two groups can reproduce and their babies can also reproduce, then they belong to the same species.

If every individual in a population has the exact same alleles, then no mechanism (selection or drift) can change the frequency of those alleles. If there is no change in frequency, then there is no evolution.

If the synthesis relies on the accumulation of small mutations and gradual shifts in the gene pool, then it supports the idea of gradualism. If this process has been happening for billions of years, then it accounts for all the diversity of life we see today.

If evolution is defined as the change in allele frequencies within a population over time, then it cannot occur within a single individual. If an individual's DNA remains constant throughout its life, then only populations can undergo modern synthesis evolution.

If scientists need a "null hypothesis" to see if evolution is happening, then they calculate the expected allele frequencies in a stable population. If those frequencies match the Hardy-Weinberg equation, then the population is in equilibrium.

If a population is physically split by a mountain or river, then the two groups can no longer exchange genes. If they evolve separately until they can no longer interbreed, then allopatric speciation has occurred.

If the synthesis required experts in birds (Mayr), genetics (Dobzhansky), and statistics (Fisher) to work together, then they are the founders. Charles Lyell was a geologist before this era, and Hooke discovered cells in the 1600s.

If any of these factors are present, then allele frequencies will change over time. If the population is large and lacks selection, mutation, or migration, then frequencies stay the same; a small population would actually experience drift.

If the Modern Synthesis moved evolution away from looking at individuals and toward looking at the math of entire groups, then it created a new field. If that field focuses on the genes of a population, then it is population genetics.

If natural selection only "sorts" existing traits, then a separate process must create them. If a random change occurs in the DNA sequence (a mutation), then a brand new version of a gene (allele) is introduced into the population.

If evolution occurs by chance rather than by fitness or adaptation, then the population has "drifted" genetically. If a small group is separated or killed off randomly, then it is an example of genetic drift.

If "gene flow" is defined as the movement of alleles between different populations, then organisms or their gametes (pollen) moving and reproducing in a new group fulfills this definition.

If a small "founding" group carries only a tiny fraction of the original gene pool's diversity, then the new population will be genetically different. If this change is caused by the identity of the starters, then it is the founder effect.