Epigenetic clocks reveal a rejuvenation event during embryogenesis followed by aging

The notion that the germ line does not age goes back to the 19th-century ideas of August Weismann. However, being metabolically active, the germ line accumulates damage and other changes over time, i.e., it ages. For new life to begin in the same young state, the germ line must be rejuvenated in the offspring. Here, we developed a multi-tissue epigenetic clock and applied it, together with other aging clocks, to track changes in biological age during mouse and human prenatal development. This analysis revealed a significant decrease in biological age, i.e., rejuvenation, during early stages of embryogenesis, followed by an increase in later stages. We further found that pluripotent stem cells do not age even after extensive passaging and that the examined epigenetic age dynamics is conserved across species. Overall, this study uncovers a natural rejuvenation event during embryogenesis and suggests that the minimal biological age (ground zero) marks the beginning of organismal aging.

The Scientific Images of the Axolotl by José María Velasco and Their Role in Nineteenth-Century Evolutionary Thinking

This paper examines the study and images of the Mexican amphibian axolotl published by the Mexican landscape painter José María Velasco in 1879. Soon thereafter Velasco encountered the study of the same amphibian written by the German Neo-Darwinist August Weismann. Velasco disputed Weismann’s evolutionary views and defended his own observations. Through an analysis of Velasco’s images, I argue that their aesthetic features were strategic to developing a biological explanation of the creature’s development. This interaction between image and scientific explanation sheds light on the significance of visual objects within the expansion of Darwinism in the late nineteenth century, and within the development of laboratory research. I argue that changes in global scientific networks and the expansion of new techniques of research necessitate a rethinking of the nexus between observation and the scientific image.

Epigenetic clocks reveal a rejuvenation event during embryogenesis followed by aging

The notion that germline cells do not age goes back to the 19th century ideas of August Weismann. However, being in a metabolically active state, they accumulate damage and other age-related changes over time, i.e., they age. For new life to begin in the same young state, they must be rejuvenated in the offspring. Here, we developed a new multi-tissue epigenetic clock and applied it, together with other aging clocks, to track changes in biological age during mouse and human prenatal development. This analysis revealed a significant decrease in biological age, i.e. rejuvenation, during early stages of embryogenesis, followed by an increase in later stages. We further found that pluripotent stem cells do not age even after extensive passaging and that the examined epigenetic age dynamics is conserved across species. Overall, this study uncovers a natural rejuvenation event during embryogenesis and suggests that the minimal biological age (the ground zero) marks the beginning of organismal aging.

Environmentally Induced Epigenetic Transgenerational Inheritance and the Weismann Barrier: The Dawn of Neo-Lamarckian Theory

For the past 120 years, the Weismann barrier and associated germ plasm theory of heredity have been a doctrine that has impacted evolutionary biology and our concepts of inheritance through the germline. Although August Weismann in his 1872 book was correct that the sperm and egg were the only cells to transmit molecular information to the subsequent generation, the concept that somatic cells do not impact the germline (i.e., the Weismann barrier) is incorrect. However, the doctrine or dogma of the Weismann barrier still influences many scientific fields and topics. The discovery of epigenetics, and more recently environmentally induced epigenetic transgenerational inheritance of phenotypic variation and pathology, have had significant impacts on evolution theory and medicine today. Environmental epigenetics and the concept of epigenetic transgenerational inheritance refute aspects of the Weismann barrier and require a re-evaluation of both inheritance theory and evolution theory.

El “darwinismo puro” de Alfred Russel Wallace: aportaciones a la teoría evolutiva moderna

La historia suele ser insistente en recordar el caso de Alfred Russel Wallace como quien, de manera secundaria, apoyó la propuesta de Darwin. Para efectos de este trabajo se presenta lo que Wallace denominó en su obra Darwinism (1889) los elementos básicos del darwinismo puro, que servirían de base para lo que George John Romanes llamaría neodarwinismo, a partir tanto del trabajo de Wallace como del de August Weismann. Esos elementos abarcan ideas que comúnmente se asocian de manera exclusiva con el trabajo de Charles Darwin, como el concepto biológico de especie, los diferentes tipos de variación y su origen, la importancia de la selección natural como el mecanismo preponderante para entender la evolución, el rechazo a los mecanismos lamarckianos, entre otros puntos. A partir de lo anterior, los objetivos de este trabajo son dos: por un lado, rescatar esos conceptos básicos del darwinismo puro de Wallace; y por el otro, establecer algunas posibles explicaciones sobre por qué persiste la idea de que el trabajo de Wallace no parece haber sido de importancia para el desarrollo de la Síntesis Moderna.

Juvenile corals inherit mutations acquired during the parent’s lifespan

Abstract128 years ago, August Weismann proposed that the only source of inherited genetic variation in animals is the germline1. Julian Huxley reasoned that if this were true, it would falsify Jean-Baptiste Lamarck’s theory that acquired characteristics are heritable2. Since then, scientists have discovered that not all animals segregate germline cells from somatic cells permanently and early in development3. In fact, throughout their lives, Cnidaria4–6 and Porifera7 maintain primordial stem cells that continuously give rise to both germline and somatic cells. The fate of mutations generated in this primordial stem cell line during adulthood remains an open question. It was unknown whether post-embryonic mutations could be heritable in animals8–10—until now. Here we use two independent genetic marker analyses to show that post-embryonic mutations are inherited in the coral Acropora palmata (Cnidaria, Anthozoa). This discovery upends the long-held supposition that post-embryonic genetic mutations acquired over an animal’s lifetime in non-germline tissues are not heritable2. Over the centuries-long lifespan of a coral, the inheritance of post-embryonic mutations may not only change allele frequencies in the local larval pool but may also spread novel alleles across great distances via larval dispersal. Thus, corals may have the potential to adapt to changing environments via heritable somatic mutations10. This mechanism challenges our understanding of animal adaptation and prompts a deeper examination of both the process of germline determination in Cnidaria and the role of post-embryonic genetic mutations in adaptation and epigenetics of modular animals. Understanding the role of post-embryonic mutations in animal adaptation will be crucial as ecological change accelerates in the Anthropocene.