Can acquired traits be inherited? What RNA science shows
Worms that inherit small RNA molecules from a virus-infected parent stay resistant for multiple generations even without the genes needed to make that RNA themselves, and a 2019 study traced a one-way signal from a worm's brain to its offspring's foraging behavior three generations later.
- What to do: Treat claims that lifestyle or trauma gets "passed down" through genes with caution until they specify a mechanism, since the proven cases so far involve small RNA in a worm, not confirmed changes to human DNA sequence.
- Why it matters: Two separate barriers, the Weismann barrier between body cells and germ cells, and epigenetic reprogramming that erases about 90% of chemical marks on DNA each generation, were long thought to make inheritance of acquired traits biologically impossible.
- How to apply it: Look for the actual carrier of information, in this case a specific small RNA matching a viral sequence, before accepting that an experience was inherited, since the effect in worms depends entirely on a protein that physically transports RNA to the next generation.
- Metrics: Small RNA-based virus resistance persisted across multiple generations in the study; the brain-to-germline effect on foraging behavior lasted three generations; roughly 90% of epigenetic marks are normally erased between generations.
- Risks: The mechanism has not been confirmed in mammals, which lack the RNA amplification system that sustains it in worms, so extrapolating these findings directly to human inheritance is premature.