Neo-Darwinism is the interpretation of Darwinian evolution through natural selection as it has variously been modified since it was first proposed. It is an attempt to reconcile Mendelian genetics, which says that organisms do not change with time, with Darwinism, which claims they do change. It has been one of the most significant, overall developments in evolutionary biology since the time of Darwin (Noble, 2011).

Darwin’s theory of natural selection was accepted. But his theory lacked an input of modern concepts of genetics and the mechanisms how characters appear and persist in a population. Later Neo-Darwinism emerged by the synthesis of original idea given by Darwin and addition of new knowledge from Mendelian genetics, molecular biology, population genetics and biological species concept. Huxley coined the phrases "evolutionary synthesis" and "modern synthesis" which were synonymously used in his semi-popular work “Evolution: The Modern Synthesis” (Noble, 2011).

Neo-darwinism considers only heritable genetic variation for evolution and explains the reasons for variation, factors for organic evolution, such as variations, mutations, natural selection, genetic drift and reproductive isolation of species. Natural selection favoured the replacement of industrial melanic moth Biston betularia f. typica with the Biston betularia  f. carbonaria due to industrialization in England. Industrial melanism in the peppered moth is one of the best examples of Darwinian evolution (Michael, 2009).

 The conceptual framework of evolutionary biology emerged with the Modern Synthesis in the early twentieth century and expanded into a highly successful research program to explore the processes of diversification and adaptation. With the advances in the field of evolutionary biology in the present era gives insight knowledge in understanding the evolution. It studies few additional factors apart from earlier one, such as evolutionary developmental biology, developmental plasticity and niche construction. In the view of evolutionary developmental biology, no gene in our body assigned first in its function, one does anything until it’s told to do and what activates the first regulatory gene is still a question. Developmental plasticity explains capacity of an organism to change its phenotype in response the environment. Niche construction is the process whereby organisms, through their activities and choices, modify their own and each other's niches (Kevin et al., 2015).

Hoelzel et al., 2002, studied impact of population bottleneck on genetic diversity of northern elephant seals by comparing haplotype diversity in control region of mitochondrial DNA. Five samples were collected from midden sites in nineteenth century used as pre-bottleneck population and compared their haplotype diversity with post-bottleneck population of 109 individuals. Measures of genetic diversity showed a loss of variation consistent with expectations and suggested a strong disruption in the pattern of allele frequencies following the bottleneck which indicate it had a quantifiable effect on genetic diversity by reduction in the variation.

Villa et al., 2019, showed experimental evolution of parasite body size over 4 years (approximately 60 generations) leads to reproductive isolation in natural populations of feather lice on birds. When lice were transferred to pigeons of different sizes, they rapidly evolved differences in body size that are correlated with host size. These size differences among lice influenced the outcome of competition between males for access to females. Results confirmed that divergent natural selection acting on a single phenotypic trait can cause reproductive isolation to emerge from a single natural population in real time.

Michael et al., 2017, examined evidence for pulsed evolution across vertebrate taxa by using maximum likelihood method to compare datasets from 66 vertebrate clades of five vertebrate group containing 8,323 extant species for fitting Levy processes. They applied different modules to know different tempo and mode of evolution like incremental change, incremental stationarity, explosive change and pulsed change. Majority of clades shown pulsed change as an evolutionary pattern which supports punctuated equilibrium model of evolution.

Field of evolutionary biology continued to evolve, allowing incorporation of new theoretical and empirical findings. As a result, today’s evolutionary theory is vastly more sophisticated than the original synthesis and covers a broader range of phenomena. However, while such progress is undeniable, it does not imply that the underlying conceptual framework allows evolutionary biologists to make the most out of progress in biology and other fields. Advances in the field of evolutionary biology broaden the doors for researchers to study and compare the evolution process from prokaryotes till the present day eukaryotes.          

References:

1. Hoelzel, A. R., Fleischer, C. R., Campagna, C., Boeuf, B. J. L. and Alvord, G., 2002, Impact of a population bottle neck on symmetry and genetic diversity in the northern elephant seals.  J. Evol. Biol., 15: 567-575.

 

2. Kevin, N. L., Tobias, U., Marcus, W. F., Sterelny, K., Gerd, B. M., Jablonka, E. and Smee, J. O., 2015, The extended evolutionary synthesis: its structure, assumptions and predictions. Pro. R. Soc. B., 282: 1-14.

3. Michael, E. N. M., 2009, Industrial melanism in the peppered moth, Bistonbetularia: An excellent teaching example of Darwinian evolution in action. Evo. Edu. Outreach., 2: 63–74.

4. Michael, J. L. and Joshua, G. S., 2017, Pulsed evolution shaped modern vertebrate body sizes. PNAS, 114(50): 13224-13229.

5. Noble, D., 2011, Neo-Darwinism, the Modern Synthesis and selfish genes: are they of use in physiology?. J. Physiol., 589(5): 1007–1015.

 

 6. Villa, S. M., Altunaa, J. C., Ruffa, J. S., Andrew, B. B., Lane, I. M., Erik, J. P., Heidi, E. C., Kevin, P. J., Michael, D. S., Sarah, E. B. and Dale, H. C., 2019, Rapid experimental evolution of reproductive isolation from a single natural population. PNAS, pp: 1-6.