Around 15 million years ago, primates such as Dryopithecus and Ramapithecus existed. According to NCERT, Dryopithecus was hairy and walked like gorillas and chimpanzees, being more ape-like, whereas Ramapithecus was more man-like.

The evolutionary convergence between placental mammals and Australian marsupials shows corresponding adaptive radiation pairs:

• Anteater corresponds to Numbat (anteater) (A-II).
• Bobcat corresponds to Tasmanian tiger cat (B-IV).
• Lemur corresponds to Spotted cuscus (C-I).
• Flying squirrel corresponds to Flying phalanger (D-III).

Five major factors are known to disrupt and affect Hardy-Weinberg equilibrium:

• Gene migration or gene flow
• Genetic drift
• Mutation
• Genetic recombination
• Natural selection
  
  'Genetic equilibrium' is the condition of stable allele frequencies itself, not an external disruptive evolutionary force.

Hugo de Vries believed that mutation causes evolution and not the minor variations that Darwin talked about. Mutations are random and directionless, whereas Darwinian variations are small and directional. De Vries called speciation by a single-step large mutation 'saltation' (jumping).