Table 2. Selected evolution misconceptions.
MisconceptionTypical phrase or statement evidencing this misconceptionPreferable languageCounterexample from A. mexicanus evolution (or correct concept)
Each trait is influenced by one Mendelian locus.“the gene for blindness”Many traits are polygenetic—determined by more than one gene.Sightedness involves multiple genes.
Individuals adapt to their environment (inheritance of acquired characteristics).“The cavefish loses its eyesight because…”Over many generations, the frequency of sightedness in a cavefish population decreases to zero because…”Individual A. mexicanus fish washed into caves by the most recent rain do not become blind in a single generation.
Natural selection involves organisms trying to adapt.“The fish are trying to get rid of what they don't need.”Individuals with beneficial traits reproduce more often and leave more offspring.Evolutionary change in A. mexicanus is the result of natural selection, pleiotropy, and genetic drift, not individual effort.
Natural selection gives organisms what they need.“The fish need to save energy so they lose their eyesight.”
“The fish lose their eyes because they don't need them.”
Individuals with beneficial traits reproduce more often and leave more offspring.Evolutionary change in A. mexicanus is the result of natural selection, pleiotropy, and genetic drift, not in response to need.
The fittest organisms in a population are those that are strongest, healthiest, fastest, and/or largest.The fittest cavefish are those that are strongest, healthiest, fastest, and/or largest.The fittest organisms are those that are best suited to survive and reproduce in a given environment.Sighted fish are the fittest in pools above ground; unsighted fish with enhanced sensory perception, etc., are the fittest cavefish.
Evolution results in progress; organisms are always getting better through evolution.Evolution strives for perfection.
Humans are the peak of evolution.
Natural selection tends to increase the frequency of those mutations that enhance the potential to survive and reproduce.Evolution in cave A. mexicanus results in LOSS of sight (regressive evolution).
Selective “pressures” directly force change in the species to occur.The lack of light forced the ancestral fish to lose their eyesight.Natural selection tends to increase the frequency of mutations that enhance the potential to survive and reproduce.The environment affects the proportion of blind A. mexicanus by selecting the individuals most suited to the cave environment.