Marion Julia Lamb (29 July 1939–12 December 2021)

Marion Julia Lamb, a pioneer in the field of evolutionary epigenetics, died in London on the 12th of December 2021 at the age of 82 of lung cancer. Marion was an original and accomplished scientist and her intellectual brilliance was combined with deep political and intellectual courage, a fascination with the natural world and an almost fanatical studiousness. Coming from a natureand bookloving working-class family, she roamed, as a child, the coasts and estuaries of East Anglia, watching birds, investigating rock pools, turning every rotten log, developing the naturalist’s ardent and focused competence. She was always grateful to her parents for the freedom they gave her and for their one demand—that she ‘does her best’—whatever ‘best’ may be. And indeed she did—from decorating her flat to gardening, sailing, teaching and researching. Her intellect was clear and powerful and she excelled in everything she ever put it to—as a 16-year-old lab assistant in Max Perutz’s lab in Cambridge during her high-school vacations, as a brilliant university student (she shared with Robin Weiss the Francis Perch Bedford Prize for the best first degree in University College London), as an inspiring teacher and as a ground-breaking scientist. Marion loved the elegant beauty of genetics, and when John Maynard Smith, her genetics teacher in University College London (UCL) suggested that she does a PhD with him, she was delighted. Her thesis on ‘Radiation and Ageing in Drosophila’ was awarded a PhD in 1965. Her laboratory research was conducted in UCL, Harwell and Birkbeck College (where she became a senior lecturer) and was concerned mainly with various aspects of the biology and genetics of ageing, using Drosophila as a research tool. Her large body of experimental work on ageing, radiation biology and mutagenesis, 25 papers altogether, stood the test of time, and she wrote a highly acclaimed, crystal-clear and concise book ‘The Biology of Ageing’ (published by Blackie, 1), on which several advanced courses in the biology of ageing around the world were based. Evolutionary biology was Marion’s passion and guide since she was a high-school student and read Huxley’s Evolution: The Modern Synthesis. She told me that the first tutorial she ever attended as a first-year student in UCL was on Waddington’s The Strategy of the Genes and that it blew her mind. Our first conversation, in 1973, also happened to be about Waddington (I discovered Waddington, independently, through reading Arthur Koestler’s Ghost in the Machine, well before I knew any genetics). I was a first-year student, and she was my genetics teacher in Birkbeck College, where I spent a year. I asked her if she knowsWaddington and she looked at me with a wry smile and suggested that I learn to walk before I start running. I ended up doing a PhD in genetics. Long before we started writing papers together, Marion sent me evolutionary biology books to Israel, and when we met we discussed the many hot topics of the time—punctuated equilibria, the sociobiology debate, the selfish gene and the neutralistselection debate. We started working together years later, in the early 1980s, exploring the evolutionary implications of epigenetic inheritance. This was not a mainstream topic (to put it mildly) and our interest in it had something to do with our background— Marion was educated in the school of British evolutionary biology, which was, in the 1950s and the early 1960s, far more open to the possibility of unorthodox modes of heredity and evolution than the American counterpart, and I came to biology because of my interest in philosophy and the great debates surrounding evolutionary theory. Our more direct motivations were related to the experimentalwork in genetics and chromatin biology thatwewere doing at the time. In late 1982, I started a PhD in the Genetics department of the Hebrew University on the relationship between DNA methylation and time of chromosomal replication. I used female cell lines where the two X chromosomes could be morphologically distinguished and asked whether the inactive X chromosome can alter its inactive, condensed chromatin conformation and its late time of replication when the cells were treated with a demethylation agent, 5-azacytidine. The answer was positive, but the chromosome-wide effect that I found was transient. This suggested that the dynamics of DNA methylation and chromatin changes are more flexible than hitherto thought. Marion was investigating at that time the effects of ageing on polytene chromosomes in Drosophila and found that chromatin structure was changed with age (unfortunately, she never published these results). We thought that the mix of stable transmissibility of chromatin states in cell lineages on the one hand and the developmental responsiveness of these states on the other open up very intriguing evolutionary questions and possibilities. We argued that it was implausible that all traces of past-induced chromatin variations would become deleted during gametogenesis. As long as totipotency is maintained, chromatin variations, just like genetic variations, could be inherited through the germ line. We reasoned that since chromatin states can be environmentally induced, chromatin variations acquired during development may be passed on between generations. Since our framework was evolutionary, we decided to look at the dynamics of X chromosome activation and inactivation during development and evolution. We focused on the developmental effects of meiotic pairing on chromatin organization and asked how chromosomal developmental dynamics affected the evolution of sex chromosomes. These investigations yielded two papers. Our first joint published paper was ‘Meiotic pairing constraints and the activity of sex chromosomes’ [2] (completed in 1986 but published in 1988 after much toing and froing) and the second