Editing Heredity (section)

===Modern development of genetics and heredity===
{{Main|History of genetics|History of evolutionary thought}}
In the 1930s, work by Fisher and others resulted in a combination of Mendelian and biometric schools into the [[Modern synthesis (20th century)|modern evolutionary synthesis]]. The modern synthesis bridged the gap between experimental geneticists and naturalists; and between both and palaeontologists, stating that:<ref>Mayr & Provine 1998</ref><ref>Mayr E. 1982. ''The growth of biological thought: diversity, evolution & inheritance''. Harvard, Cambs. pp. 567 et seq.</ref>

# All evolutionary phenomena can be explained in a way consistent with known genetic mechanisms and the observational evidence of naturalists.
# Evolution is gradual: small genetic changes, recombination ordered by [[natural selection]]. Discontinuities amongst species (or other taxa) are explained as originating gradually through geographical separation and extinction (not saltation).
# [[Natural selection|Selection]] is overwhelmingly the main mechanism of change; even slight advantages are important when continued. The object of selection is the [[phenotype]] in its surrounding environment. The role of [[genetic drift]] is equivocal; though strongly supported initially by [[Dobzhansky]], it was downgraded later as results from ecological genetics were obtained.
# The primacy of population thinking: the genetic diversity carried in natural populations is a key factor in evolution. The strength of natural selection in the wild was greater than expected; the effect of ecological factors such as niche occupation and the significance of barriers to gene flow are all important.

The idea that [[speciation]] occurs after populations are reproductively isolated has been much debated.<ref>{{cite journal | title=Genetic Divergence, Reproductive Isolation, and Marine Speciation | author=Palumbi, Stephen R. | author-link = Stephen Palumbi | journal=Annual Review of Ecology and Systematics | date=1994 | volume=25 | pages=547–572 | doi=10.1146/annurev.es.25.110194.002555}}</ref> In plants, polyploidy must be included in any view of speciation. Formulations such as 'evolution consists primarily of changes in the [[allele frequency|frequencies of alleles]] between one generation and another' were proposed rather later. The traditional view is that developmental biology ('[[evo-devo]]') played little part in the synthesis, but an account of [[Gavin de Beer]]'s work by [[Stephen Jay Gould]] suggests he may be an exception.<ref>Gould S.J. ''Ontogeny and phylogeny''. Harvard 1977. pp. 221–222</ref>

Almost all aspects of the synthesis have been challenged at times, with varying degrees of success. There is no doubt, however, that the synthesis was a great landmark in evolutionary biology.<ref>{{cite journal | title=Evolution – The Extended Synthesis. A research proposal persuasive enough for the majority of evolutionary biologists? | author=Handschuh, Stephan | author2=Mitteroecker, Philipp | journal= Human Ethology Bulletin|date=June 2012 | volume=27 | issue=1–2 | pages=18–21 | issn=2224-4476}}</ref> It cleared up many confusions, and was directly responsible for stimulating a great deal of research in the post-[[World War II]] era.

[[Trofim Lysenko]] however caused a backlash of what is now called [[Lysenkoism]] in the [[Soviet Union]] when he emphasised [[Lamarckian]] ideas on the [[inheritance of acquired traits]]. This movement affected agricultural research and led to food shortages in the 1960s and seriously affected the USSR.<ref>{{Cite journal|last=Harper|first=Peter S.|date=2017-08-03|title=Human genetics in troubled times and places|journal=Hereditas|volume=155|pages=7|doi=10.1186/s41065-017-0042-4|issn=1601-5223|pmc=5541658|pmid=28794693 |doi-access=free }}</ref>

There is growing evidence that there is transgenerational inheritance of epigenetic changes in humans<ref>{{cite journal|last1=Szyf|first1=M|title=Nongenetic inheritance and transgenerational epigenetics|journal=Trends in Molecular Medicine|date=2015|volume=21|issue=2|pages=134–144|doi=10.1016/j.molmed.2014.12.004|pmid=25601643}}</ref> and other animals.<ref>{{cite journal|last1=Kishimoto|first1=S|display-authors= etal|title=Environmental stresses induce transgenerationally inheritable survival advantages via germline-to-soma communication in Caenorhabditis elegans|journal=Nature Communications|date=2017|volume=8|doi=10.1038/ncomms14031|pmid=28067237|page=14031|hdl=2433/217772|bibcode=2017NatCo...814031K|pmc=5227915}}</ref>