Marion Lamb

Not all of the information that is transmitted between generations of cells and organisms is encoded in DNA sequences. Information is also transmitted through epigenetic systems, which include the non-DNA parts of chromosomes, self-sustaining metabolic loops, self-propagating protein structures, and small RNA molecules. Some of the properties of ep...

Ideas about heredity and evolution are undergoing a revolutionary change. New findings in molecular biology challenge the gene-centered version of Darwinian theory according to which adaptation occurs only through natural selection of chance DNA variations. In Evolution in Four Dimensions, Eva Jablonka and Marion Lamb argue that there is more to he...

A pioneering proposal for a pluralistic extension of evolutionary theory, now updated to reflect the most recent research. This new edition of the widely read Evolution in Four Dimensions has been revised to reflect the spate of new discoveries in biology since the book was first published in 2005, offering corrections, an updated bibliography, and...

The attitude of biologists to the history of their discipline varies. For some, a hazy knowledge of the recent past is all that is necessary to provide an explanatory basis for their work. They take it for granted that everything of value from the less recent past has been appropriately incorporated into present-day thinking. Other biologists see h...

This chapter reports the case of transgenerational epigenetic inheritance. It concentrates on developmental biology, in particular on molecular studies of epigenetics, and on one specific challenge: That of “soft inheritance.” The chapter reviews the assumptions about heredity and development that were built into the late twentieth-century version...

Comparisons have been made between the mutagenic efficiency in Drosophila of 600 meV protons and 250 kvp x-rays. Second chromosome recessive lethal mutation frequencies were measured in 6 successive 3-day broods of offspring. There was no evidence of any difference between the effectiveness of x-rays and protons from the initial beam or from the Br...

This paper presents some of the recent challenges to the Modern Synthesis of evolutionary theory, which has domi-nated evolutionary thinking for the last sixty years. The focus of the paper is the challenge of soft inheritance -the idea that variations that arise during development can be inherited. There is ample evidence showing that phenotypic v...

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, as evolutionary theory was developed further, heredity became identified with genetics, and variation was seen in terms of combinations of randomly generated gene mutations. We arg...

The commentaries on Evolution in Four Dimensions reflect views ranging from total adherence to gene-centered neo-Darwinism, to the acceptance of non-genetic and Lamarckian processes in evolution. We maintain that genetic, epigenetic, behavioral, and cultural variations have all been significant, and that the developmental aspects of heredity and ev...

In responding to three reviews of Evolution in Four Dimensions (Jablonka and Lamb, 2005, MIT Press), we briefly consider the historical background to the present genecentred view of evolution, especially the way in which Weismann’s theories have influenced it, and discuss the origins of the notion of epigenetic inheritance. We reaffirm our belief t...

Maynard Smith and Szathmáry's analysis of the major transitions in evolution was based on changes in the way information is stored, transmitted and interpreted. With the exception of the transition to human linguistic societies, their discussion centred on changes in DNA and the genetic system. We argue that information transmitted by non-genetic m...

We discuss the role of cell memory in heredity and evolution. We describe the properties of the epigenetic inheritance systems (EISs) that underlie cell memory and enable environmentally and developmentally induced cell phenotypes to be transmitted in cell lineages, and argue that transgenerational epigenetic inheritance is an important and neglect...

We discuss the changing use of epigenetics, a term coined by Conrad Waddington in the 1940s, and how the epigenetic approach to development differs from the genetic approach. Originally, epigenetics referred to the study of the way genes and their products bring the phenotype into being. Today, it is primarily concerned with the mechanisms through...

Keywords:Epigenetic inheritance;Lamarckism;somatic selection;acquired characters;post-zygotic isolation

We discuss the role of cell memory in heredity and evolution. We describe the properties of the epigenetic inheritance systems (EISs) that underlie cell memory and enable environmentally and developmentally induced cell phenotypes to be transmitted in cell lineages, and argue that transgenerational epigenetic inheritance is an important and neglect...

Cytosine methylation is widely distributed in multicellular organisms. We present a comprehensive survey of the existing data on the phylogenetic distribution of DNA methylation in invertebrates, together with new data for the crustacean Penaeus semisulcatus, the annelid Aporrectodea caliginosa trapezoides, and the parasitic platyhelminth Schistoso...

Since the Modern Synthesis, evolutionary biologists have assumed that the genetic system is the sole provider of heritable variation, and that the generation of heritable variation is largely independent of environmental changes. However, adaptive mutation, epigenetic inheritance, behavioural inheritance through social learning, and language-based...

Adaptive evolution is usually assumed to be directed by selective processes, development by instructive processes; evolution involves random genetic changes, development involves induced epigenetic changes. However, these distinctions are no longer unequivocal. Selection of genetic changes is a normal part of development in some organisms, and thro...

c1 Marion Lamb, Biology Department, Birkbeck College, Malet Street, London WC1E 7HX, UK.

Several different types of epigenetic inheritance system enable alternative functional states to be maintained in cell lineages that have identical DNA sequences. Both random and guided (directed) epigenetic variations can be transmitted by these systems, and lead to heritable modifications in cell structure and function. Although it is usually ass...

Studies of reproductive isolation between animal species have shown (i) that if one sex of the hybrids between two species is sterile or inviable, it is usually the heterogametic sex (Haldane's rule), and (ii) the genes on the sex chromosomes play a particularly large role in hybrid sterility and inviability. We propose an explanation for these two...

The facts and ideas which have been discussed lead to the following synthesis and model. Heteromorphic sex chromosomes evolved from a pair of homomorphic chromosomes which had an allelic difference at the sex‐determining locus. The first step in the evolution of sex‐chromosome heteromorphism involved either a conformational or a structural differen...

Although it is usually assumed that Lamarckian inheritance does not and cannot occur, molecular mechanisms by which non-mutational changes acquired in one generation can be transmitted to the next are now known. These mechanisms involve changes in chromatin structure, rather than changes in DNA base sequence. It is argued that some parental-age eff...

There is evidence that the functional history of a gene in one generation can influence its expression in the next. In somatic cells, changes in gene activity are frequently associated with changes in the pattern of methylation of the cytosines in DNA; these methylation patterns are stably inherited. Recent work suggests that information about patt...

The state of activity and condensation of the sex chromosomes in gametocytes is frequently different from that found in somatic cells. For example, whereas the X chromosomes of XY males are euchromatic and active in somatic cells, they are usually condensed and inactive at the onset of meiosis; in the somatic cells of female mammals, one X chromoso...

In 1939 Russ and Scott published a report on the long-term effects on rats of chronic exposure to gamma rays. In it they showed that not only was the death rate of the irradiated animals higher than that of the controls during the 24-week exposure period, but it remained higher even after irradiation had ceased. Furthermore,’ six months after the e...

By continuously monitoring the weight loss in dry air at 24.5°C of active individual male Drosophila melanogaster, it was shown that: (i) during the active period, weight loss is a linear function of time, but once the body water content is reduced to below a critical level, activity ceases and the rate of weight loss increases rapidly; the time at...

Virgin female Sarcophaga carnaria maintained on a diet of sugar and water had shorter lifespans than those maintained on a liver, sugar and water diet; there was no significant different between the lifespans of mated females or mated males kept on the two diets. Autoradiographs of mid-gut sections from virgin females which had been fed with [3H]th...

The amounts of DNA in midgut and Malpighian tubule cells of adult maleDrosophila melanogaster have been determined by Feulgen-DNA cytophotometry. The DNA values fall into discrete classes reflecting different levels of polyteny. The maximum level is 64C in the midgut, 256C in Malpighian tubules, and the modal values are 32C and 128C respectively. T...

The widely used fungicide benomyl (methyl-1-(butylcarbamoyl)-2-benzimidazole carbamate) and its breakdown product methyl-2-benzimidazole carbamate (MBC) have been reported to have mutagenic activity in some organisms. In experiments with Drosophila melanogaster we found (i) there was no significant increase in recessive lethal frequency after feedi...

As Drosophila melanogaster ages, the amount of food eaten per day increases. The amount of uric acid excreted falls, probably because there is a decline in the efficiency of synthesis. Reserves of body fat and glycogen also fall. These changes are found both for flies kept on a high fat/low carbohydrate diet and for those kept on a low fat/high car...

The organophosphorus insecticide metrifonate (O,O-dimethyl(1-hydroxy-2,2,2-trichloroethyl)phosphonate), also known as trichlorfon or Dipterex ®, was tested for its ability to induce sex-linked and autosomal recessive lethal mutations in Drosophila melanogaster. There was no evidence of an increase in the frequency of lethal mutations after feeding...

Age-related changes in the water content of adult male Drosophila melanogaster which had been irradiated when they were 2 days old with 35 krad 60Co γ-rays have been compared with those found in unirradiated flies. During the first 8 days of life the average water content fell from over 3·0 to about 2·0 mg water/mg dry weight. Thereafter the averag...

The survival times in dry air at 35°C of adult male Drosophila melanogaster which had been irradiated when 2 days old with 35 krad 60Co γ-rays were compared with those of unirradiated control flies. With increase in age survival times decreased for both control and irradiated flies, but until middle age the irradiated flies survived longer than the...

PREVIOUS investigations of the cumulative effect of irradiation on the fitness of Drosophila populations have concentrated mainly on changes in fitness during the pre-adult stages. In this paper we describe the results of a study of changes in what may be considered as another aspect of fitness, adult lifespan. The irradiated populations which prov...

Data are presented showing that the reduction in life span of male Drosophila melanogaster produced by a given dose of radiation is smaller for doses given later in life. This suggests the hypothesis that radiation shortens life by accelerating subsequent ageing, so that the reduction in life span for small doses is proportional to the dose and to...

HOLLINGSWORTH1 has reported the results of an experiment with Drosophila melanogaster which he claims are not consistent with either of the two theories which have been suggested to explain the fact that poikilothermous animals have a shorter lifespan at high temperatures than at low temperatures. These two theories are the rate of living theory fi...

Adult male Drosophila melanogaster were irradiated with doses of up to 1000 rad of X-rays or neutrons (+10%γ-rays) and germ cells irradiated at pre-meiotic and post-meiotic stages were tested for the presence of 11nd chromosome recessive lethals by the Cy/B1 L method. Lethal mutations found in sperm irradiated at the premeiotic stages were tested f...

Experiments which investigated the effect of X-ray doses up to 60,000 rad on the further expectation of life of triploid and two classes of diploid adult female Drosophila melanogaster are described. Low doses produced an increase in the further expectation of life of triploid and of one of the classes of diploid females, but higher doses produced...

It does not seem possible at present to decide whether radiation reduces the life span of insects primarily by causing mutations in the nuclei of somatic cells. But some tentative conclusions can be drawn: (i) The theory that life-shortening is primarily due to recessive somatic mutations can be rejected, for two reasons. First, if the theory were...

The longevity of adult male and virgin female Drosophila subobscura exposed to single doses of X-rays 4–8 days after eclosion has been investigated. When kept on a maize meal-agar-molasses medium which was replaced every 4 days, males showed a nearly linear reduction in lifespan with increasing dose; females showed an increase in lifespan after dos...