In his theory of evolution, Darwin recognized that the conditions of life play a role in the generation of hereditary variations as well as in their selection. However, since the mid 20th century, the Modern Synthesis version of Darwinism expelled developmental responses to environmental changes from the study of heritable variation. It identifi ed heredity with genetics, with hereditary variation being seen in terms of combinations of randomly generated gene mutations. This view has dominated evolutionary theorizing for the last sixty years. Since the 1990s, data coming from developmental biology (particularly the molecular aspects of differentiation and morphogenesis), from ecology (in particular ideas about niche construction and studies of symbiosis), from behavior (where the transmission of information through social learning is a major focus), and from cultural studies (where the relation between cultural evolution and genetic evolution is under scrutiny) is challenging the modern synthesis view. Marion Lamb and I devoted our recent book Evolution in Four Dimensions to this challenge, and identifi ed four types of inheritance (genetic, epigenetic, behavioral, and symbol-based), each of which can provide variations on which natural selection will act. Some of these variations arise in response to developmental and environmental conditions, so developmentally induced or reconstructed heritable variations can be selected and lead to changes in the nature and frequency of phenotypes in populations. Furthermore, under certain conditions, the mechanisms underlying epigenetic inheritance can also lead to the reorganization of the epigenome. In this lecture I review the challenge that comes from the work on epigenetics carried out since the late 1980s, discuss different types of epigenetic inheritance mechanisms, examine the prevalence, stability and inducibility of cellular epigenetic variants, and point to some of the ways in which epigenetic mechanisms have affected micro- and macro-evolution.

V svoji teoriji o evoluciji je Darwin izpostavil vlogo življenjskih razmer v nastanku dednih razlik in v njihovi selekciji. Od sredine 20. stoletja dalje je moderna sinteza darvinizma izključila razvojne odgovore na okoljske spremembe iz študij o dednih razlikah. Dedovanje je izenačila z genetiko, dedne razlike pa opisovala kot kombinacije naključnih genskih mutacij. Ta pogled je prevladoval v evolucijskih polemikah zadnjih šestdeset let. Od devetdesetih let dalje novi podatki iz razvojne biologije (predvsem molekularni vidiki diferenciacije in morfogeneze), ekologije (ustvarjanje niš, raziskave simbioze), raziskav vedenja (prenos informacij prek socialnega učenja) in kulturoloških raziskav (povezave med genetsko in kulturno evolucijo) spreminjajo pogled moderne sinteze. Z Marion Lamb sva o teh izzivih pisali v najini knjigi Evolution in Four Dimensions, v kateri sva določili štiri tipe dedovanja (genetsko, epigenetsko, vedenjsko in simbolno), od katerih lahko vsak predstavlja vir razlik, na katerih deluje naravni izbor. Nekatere od teh razlik izvirajo iz razvojnih in okoljskih razmer, kar vodi v spremembe v naravi in v frekvenci fenotipov v populaciji. Nadalje lahko mehanizmi, ki so odgovorni za epigenetsko dedovanje, pod določenimi pogoji vodijo v reorganizacijo epigenoma. V tem predavanju bom predstavila pregled epigenetskih raziskav od poznih osemdesetih let naprej, nadalje bom predstavila različne tipe oz. mehanizme epigenetskega dedovanja, prevalenco, stabilnost in inducibilnost različnih epigenetskih variant in izpostavila nekatere načine, s katerimi so epigenetski mehanizmi vplivali na mikro- in makroevolucijo.