The myth of the goldfish’s three second memory has long prevailed in popular culture. However, new research has suggested that unlike humans, fish are able to conserve memories over generations using epigenetic mechanisms.

Epigenetic modifications can change the expression of DNA without changing the DNA code itself. Often this is in the form of DNA methylation, where methyl groups are added to the DNA bases and change the way the cell machinery read the DNA code. These changes can be bought about by a range of environmental and lifestyle factors.

Previous research has suggested that although epigenetic modifications in humans can be acquired over the course of a lifetime, the modifications are not passed onto the next generation. This is due to methylation erasure events during human development. However, in fish epigenetic modifications are conserved in their offspring allowing them to pass down their life experiences to the next generation.

When fish are developing, exposure to altered environmental condition such as heat can change the sex of the fish. Even if the fish has the ZW sex chromosomes that make it genetically female, epigenetic changes can cause the fish to develop into a male phenotype whilst remaining genetically female.

Interestingly, there is growing evidence that epigenetic modifications can be passed down in humans to some extent. Pregnant mothers that experience famine give birth to children who experience higher levels of coronary heart disease, obesity and schizophrenia than the rest of the population. Studies in mice indicate that the when parent mice experience trauma their offspring inherited the trauma effects.

Further research is required to understand how genetic changes are conserved across generations. As many diseases have an epigenetic basis, the research could help develop more effective treatments.