Evolutionary Theories: From Lamarck to Punctuated Equilibrium
Hypotheses of Evolution
Lamarckism
Lamarck’s transformisme theory proposed that organisms evolve through the inheritance of acquired characteristics. For example, a worm transforming into a beetle over time or an animal adapting to a contaminated environment.
Evidence of Evolution
Darwin posited that living beings are products of a process involving successive modifications from a common ancestor, driven by natural selection.
Paleontological Evidence
Fossil remains of extinct flora and fauna demonstrate evolutionary change across geological layers.
Comparative Anatomy
Homologous structures in different species suggest a common origin and developmental path.
Comparative Biochemistry
Biochemical homologies provide strong evidence for evolutionary relationships.
Embryological Evidence
Similar embryonic characteristics across species suggest common ancestry.
Adaptation and Mimicry
The peppered moth’s adaptation to industrial pollution exemplifies natural selection. Mimicry allows animals to avoid detection through camouflage.
Geographical Distribution
The uneven distribution of species reflects geographical barriers and dispersal mechanisms.
Evidence of Domestication
Human agricultural and livestock practices demonstrate human-induced evolutionary changes.
Neo-Darwinism
Initially, neo-Darwinism emphasized natural selection as the exclusive mechanism of evolution, opposing Lamarckian ideas. Later, it became associated with the modern evolutionary synthesis of the 1930s.
August Weismann distinguished between the hereditary germ plasm and the soma, arguing that acquired characteristics are not inherited.
Punctuated Equilibrium
Proposed by Niles Eldredge and Stephen Jay Gould in 1972, punctuated equilibrium suggests that species remain stable for long periods (stasis) and undergo rapid evolutionary change during speciation.
Key Proponents
- Niles Eldredge: Initially studied Latin philology before shifting to anthropology.
- Stephen Jay Gould: Co-authored “Punctuated Equilibria” (1972) and “Evolutionary Theory and the Rise of American Paleontology” (1974), arguing for non-uniform evolutionary rates.