symmetric mutants, which arise when lcyc is heavily methylated. given the importance of floral shape to pollinators, methylation of lcyc homologues (e.g. cycloidea) may have deleterious effects on plant fitness. in animals, numerous studies have shown that inherited epigenetic marks can increase susceptibility to disease. transgenerational epigenetic influences are also suggested to contribute to disease, especially cancer, in humans. tumor methylation patterns in gene promoters have been shown to correlate positively with familial history of cancer. furthermore, methylation of the msh2 gene is correlated with early-onset colorectal and endometrial cancers. putatively adaptive effects experimentally demethylated seeds of the model organism arabidopsis thaliana have significantly higher mortality, stunted growth, delayed flowering, and lower fruit set, indicating that epigenes may increase fitness. furthermore, environmentally induced epigenetic responses to stress have been shown to be inherited and positively correlated with fitness. in animals, communal nesting changes mouse behavior increasing parental care regimes and social abilities that are hypothesized to increase offspring survival and access to resources (such as food and mates), respectively. inheritance of immunity epigenetics play a crucial role in regulation and development of the immune system. in 2021, evidence of inheritance of trained immunity across generations to progeny of mice with a systemic infection of candida albicans was provided. the progeny of mice survived the candida albicans infection via functional, transcriptional, and epigenetic changes linked to the immune gene loci. the responsiveness of myeloid cells to the candida albicans infection increased in inflammatory pathways, and resistance was increased to infections in the next generations. immunity in vertebrates can also be transferred from maternal through the passing of hormones, nutrients and antibodies. in mammals, the maternal factors can be transferred via lactation or the placenta. the transgenerational transmission of immune-related traits are also described in plants and invertebrates. plants have a defense priming system which enables them to have an alternate defense response that can be accelerated upon exposure to stress actions or pathogens. after the event of priming, priming stress clue information is stored, and the memory may be inherited in the offspring (intergenerational or transgenerational). in studies, the progeny of pseudomonas syringae infected arabidopsis were primed during the expression of systemic acquired resistance (sar). the progeny showed to have resistance against (hemi)-biotrophic pathogens which is associated with salicylic dependent genes and the defense regulatory gene, non expressor of pr genes (npr1). transgenerational sar in the progeny was associated with increased acetylation of histone 3 at lysine 9, hypomethylation of genes, and chromatin marks on promoter regions of salicylic dependent genes. similarly in insects, the red flour beetle trifolium castoreum is primed through the exposure of the pathogen bacillus thuringiensis. double-mating experiments with the red flour beetle demonstrated that paternal transgenerational immune priming is mediated by sperm or seminal fluid which enhances survival upon exposure to pathogens and contribute to epigenetic changes. feedback loops and tei positive and negative feedback loops are commonly observed in molecular mechanisms and regulation of homeostatic processes. there is evidence that feedback loops interact to maintain epigenetic modifications within one generation, as well as contributing to tei in various organisms, and these feedback loops can showcase putative adaptations to environmental perturbances. feedback loops are truly a repercussion of any epigenetic modification, since it results in changes in expression. even more so, the feedback loops seen across multiple generations because of tei showcases a spatio-temporal dynamic that is associated with tei alone. for example, elevated temperatures during embryogenesis and piwi rna (pirna) establishment are directly proportional, providing a heritable outcome for repressing transposable elements via pirna clusters. furthermore, subsequent generations retain an active locus to continue establishing pirna, which its formation was previously enigmatic. in another case, it was suggested that endocrine disruption had a feedback loop interaction with methylation of varying genomic sites in menidia beryllina, which may have been a function of tei. when exposure was removed, and m. beryllina f2 offspring still retained these methylation marks, which caused a negative feedback loop on expression of various genes. in another example, hybridization of eels can lead to feedback loops contributing to transposon demethylation and transposable element activation. because te's are typically silenced in the genome, their presence and potential expression creates a feedback loop to prevent hybrids from reproducing with other hybrids or non-hybrid species, which eliminates the proliferation of te expression and prevents tei in this context. this phenomenon is known as a form of post-zygotic reproductive isolation. macroevolutionary patterns inherited epigenetic effects on phenotypes have been well documented in bacteria, protists, fungi, plants, nematodes, and fruit flies. though no systematic study of epigenetic inheritance has been conducted (most focus on model organisms), there is preliminary evidence that this mode of inheritance is more important in plants than in animals. the early differentiation of animal germlines is likely to preclude epigenetic marking occurring later in development, while in plants and fungi somatic cells may be incorporated into the germ line. it is thought that transgenerational epigenetic inheritance can enable certain populations to readily adapt to variable environments. though there are well documented cases of transgenerational epigenetic inheritance in certain populations, there are questions to whether this same form of adaptability is applicable to mammals. more specifically, it is questioned if it applies to humans. as of late, most of the experimental models utilizing mice and limited observations in humans have only found epigenetically inherited traits that are detrimental to the health of both organisms. these harmful traits range from increased risk of disease, such as cardiovascular disease, to premature death. however, this may be based on the premise of limited reporting bias because it is easier to detect negative experimental effects, opposed to positive experimental effects. furthermore, considerable epigenetic reprogramming necessary for the evolutionary success of germlines and the initial phases of embryogenesis in mammals may be the potential cause limiting transgenerational inheritance of chromatin marks in mammals. life history patterns may also contribute to the occurrence of epigenetic inheritance. sessile organisms, those with low dispersal capability, and those with simple behavior may benefit most from conveying information to their offspring via epigenetic pathways. geographic patterns may also emerge, where highly variable and highly conserved environments might host fewer species with important epigenetic inheritance. controversies humans have long recognized that traits of the parents are often seen in offspring. this insight led to the practical application of selective breeding of plants and animals, but did not address the central question of inheritance: how are these traits conserved between generations, and what causes variation? several positions have been held in the history of evolutionary thought. blending vs. particulate inheritance blending inheritance leads to the averaging out of every characteristic, which as the engineer fleeming jenkin pointed out, makes evolution by natural selection impossible. addressing these related questions, scientists during the time of the enlightenment largely argued for the blending hypothesis, in which parental traits were homogenized in the offspring much like buckets of different colored paint being mixed together. critics of charles darwin's on the origin of species, pointed out that under this scheme of inheritance, variation would quickly be swamped by the majority phenotype. in the paint bucket analogy, this would be seen by mixing two colors together and then mixing the resulting color with only one of the parent colors 20 times; the rare variant color would quickly fade. unknown to most of the european scientific community, the monk gregor mendel had resolved the question of how traits are conserved between generations through breeding experiments with pea plants. charles darwin thus did not know of mendel's proposed "particulate inheritance" in which traits were not blended but passed to offspring in discrete units that we now call genes. darwin came to reject the blending hypothesis even though his ideas and mendel's were not unified until the 1930s, a period referred to as the modern synthesis. inheritance of innate vs. acquired characteristics in his 1809 book, philosophie zoologique, jean-baptiste lamarck recognized that each species experiences a unique set of challenges due to its form and environment. thus, he proposed that the characters used most often would accumulate a "nervous fluid." such acquired accumulations would then be transmitted to the individual's offspring. in modern terms, a nervous fluid transmitted to offspring would be a form of epigenetic inheritance. lamarckism, as this body of thought became known, was the standard explanation for change in species over time when charles darwin and alfred russel wallace co-proposed a theory of evolution by natural selection in 1859. responding to darwin and wallace's theory, a revised neo-lamarckism attracted a small following of biologists, though the lamarckian zeal was quenched in large part due to weismann's famous experiment in which he cut off the tails of mice over several successive generations without having any effect on tail length. thus the emergent consensus that acquired characteristics could not be inherited became canon. revision of evolutionary theory non-genetic variation and inheritance, however, proved to be quite common. concurrent with the 20th-century development of the modern evolutionary synthesis (unifying mendelian genetics and natural selection), c. h. waddington (1905-1975) was working to unify developmental biology and genetics. in so doing, he adopted the word "epigenetic" to represent the ordered differentiation of embryonic cells into functionally distinct cell types despite having identical primary structure of their dna. researchers discussed waddington's epigenetics sporadically - it became more of a catch-all for puzzling non-genetic heritable characters rather than a concept advancing the body of inquiry. consequently, the definition of waddington's word has itself evolved, broadening beyond the subset of developmentally signaled, inherited cell specialization. some scientists have questioned whether epigenetic inheritance compromises the foundation of the modern synthesis. outlining the central dogma of molecular biology, francis crick succinctly stated, "dna is held in a configuration by histone so that it can act as a passive template for the simultaneous synthesis of rna and protein. none of the detailed 'information' is in the histone." however, he closes the article stating, "this scheme explains the majority of the present experimental results!" indeed, the emergence of epigenetic inheritance (in addition to advances in the study of evolutionary-development, phenotypic plasticity, evolvability, and systems biology) has strained the current framework of the modern evolutionary synthesis, and prompted the re-examination of previously dismissed evolutionary mechanisms. furthermore, patterns in epigenetic inheritance and the evolutionary implications of the epigenetic codes in living organisms are connected to both lamarck's and darwin's theories of evolution. for example, lamarck postulated that environmental factors were responsible for modifying phenotypes hereditarily, which supports the constructs that exposure to environmental factors during critical stages of development can result in epimutations in germlines, thus augmenting phenotypic variance. in contrast, darwin’s theory claimed that natural selection strengthened a populations ability to survive and remain reproductively fit by favoring populations that are able to readily adapt. this theory is consistent with intergenerational plasticity and phenotypic variance resulting from heritable adaptivity. in addition, some epigenetic variability may provide beneficial plasticity, so that certain organisms can adapt to fluctuating environmental conditions. however, the exchange of epigenetic information between generations can result in epigenetic aberrations, which are epigenetic traits that deviate from the norm. therefore, the offspring of the parental generations may be predisposed to specific diseases and reduced plasticity due to epigenetic aberrations. though the ability to readily adapt when faced with a new environment may be beneficial to certain populations of species that can quickly reproduce, species with long generational gaps may not benefit from such an ability. if a species with a longer generational gap does not appropriately adapt to the anticipated environment, then the reproductive fitness of the offspring of that species will be diminished. there has been critical discussion of mainstream evolutionary theory by edward j steele, robyn a lindley and colleagues, fred hoyle and n. chandra wickramasinghe, yongsheng liu denis noble, john mattick and others that the logical inconsistencies as well as lamarckian inheritance effects involving direct dna modifications, as well as the just described indirect, viz. epigenetic, transmiss'ions, challenge conventional thinking in evolutionary biology and adjacent fields.