A new study has revived a long-standing controversy over the evolution of living beings between the French naturalist Jean-Baptiste Lamarck and Charles Darwin.
The team experimented with rice plants and demonstrated that they can pass on learned survival traits to their offspring. This finding confirms Lamarck’s hypothesis and challenges the idea that evolution occurs solely through random genetic variation, as Darwin maintained.
Lamarck and Darwin proposed theories of evolution in the 19th century that have decisively influenced our understanding of evolution to this day. Both opposed the prevailing belief at the time, which assumed the immutability of species, and argued that life forms inevitably change over time.
However, their explanations of how evolution occurs were fundamentally different and are often considered irreconcilable.
A Rivalry That Lasts for Centuries
Lamarck, with his famous theory of giraffes, claimed that these animals’ necks grew so long because they had to stretch to reach the highest leaves in trees. This acquired (epigenetic) trait was passed on to subsequent generations, who also had long necks.
Darwin’s theory of evolution, by contrast, is based on natural selection. The naturalist argued that individuals in a population vary naturally and randomly, and that those specimens with traits best adapted to their environment are more likely to survive and reproduce. This theory has become the dominant scientific explanation for understanding evolution.
For Darwin, giraffes with longer necks could reach more food and were more likely to survive and reproduce, passing this genetic trait on to their offspring.
The recent research by the team from the Chinese Academy of Sciences, published in the prestigious journal Cell, is not the first to reinforce the Lamarckian idea of epigenetic inheritance (the transmission of traits through mechanisms other than changes in the DNA sequence). But it is one of the most direct and robust scientific demonstrations to date of this theory in a natural system.
Frost-Resistant Rice
The team has been able to demonstrate that rice varieties grown in the frigid northeast of China are able to adapt to these extreme conditions in a stable, non-genetic manner. Rice plants are generally very sensitive to low temperatures, and these conditions negatively affect their growth and yield.
The researchers examined several varieties of Asian rice and selected one that was more sensitive to cold and produced fewer seeds in these environments. The team subjected the still-growing plants to cold stress for a week and then allowed them to grow at normal temperatures.
They then collected the seeds from the highest-yielding plant and germinated them again, subjecting them to a low-temperature treatment. The third generation of these plants, they claim, continued to show cold tolerance, which can be maintained for at least five generations, the study indicates.
Irrefutable Proof
These findings led the researchers to study the epigenetic differences between the varieties to discover the cause of their adaptation to cold. The team discovered that the low-temperature-tolerant variety had less DNA methylation, a chemical modification that regulates gene activity.
Specifically, they observed that cold stress reduced methylation near the ACT1 (Acquired Cold Tolerance 1) gene, which plays a crucial role in resistance to low temperatures. They then used epigenome editing tools to modify rice grown at normal temperatures. The results confirmed that this change directly improves cold tolerance by increasing the expression of ACT1.
Later, they restored the original DNA methylation, and the rice plants lost their ability to resist cold. This, the research team says, demonstrates a direct relationship between epigenetic change and cold tolerance.
“Cold-induced alterations in DNA methylation and ACT1 expression in response to cold are stably inherited and are associated with acquired cold tolerance,” the team states in the study.
However, they admit that further in-depth research into these genetic mechanisms is still needed to fully understand how they work.